ORCID Profile
0000-0001-5180-1041
Current Organisation
Monash University
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Analytical Chemistry | Separation Science | Separation Science | Biological And Medical Chemistry | Analytical Spectrometry | Environmental Science and Management | Other Instrumental Methods | Natural Products Chemistry | Instrumental Methods (excl. Immunological and Bioassay Methods) | Chemical Spectroscopy | Organic Chemical Synthesis | Chemical Sciences not elsewhere classified | Chemical Sciences Not Elsewhere Classified | Food Chemistry and Molecular Gastronomy (excl. Wine) | Causes and Prevention of Crime | Environmental Impact Assessment | Environmental Management And Rehabilitation | Instruments And Techniques | Organic Geochemistry Not Elsewhere Classified | Forensic Chemistry | Pharmaceutical Sciences And Pharmacy | Analytical Biochemistry | Environmental Chemistry (incl. Atmospheric Chemistry) | Environmental Monitoring | Civil Geotechnical Engineering | Medicinal and Biomolecular Chemistry | Electroanalytical Chemistry | Environmental Technologies | Chemometrics | Civil Engineering | Theoretical And Computational Chemistry Not Elsewhere Classified | Organic Chemistry not elsewhere classified | Atmospheric Sciences Not Elsewhere Classified
ANZSRC Socio-Economic Objective (SEO)
Chemical sciences | Scientific instrumentation | Expanding Knowledge in the Chemical Sciences | Essential Oils (e.g. Tea Tree, Eucalyptus, Lavender, Peppermint, Boronia, Sandalwood) | Primary plant products not elsewhere classified | Environmental Management Systems | Emerging Defence Technologies | National Security | Air quality | Physical and Chemical Conditions of Water for Urban and Industrial Use | Environmental education and awareness | Treatments (e.g. chemicals, antibiotics) | Fresh, Ground and Surface Water Flora, Fauna and Biodiversity | Other | Technological and organisational innovation | Oils and Fats (incl. Margarines) | Higher education | Integrated (ecosystem) assessment and management | Biofuel (Biomass) Energy | Oil and Gas Refining | Ecosystem Assessment and Management of Urban and Industrial Environments | Industrial Energy Conservation and Efficiency | Environmental health | Scientific Instruments | Treatments (e.g. chemicals, antibiotics) |
Related Links
Publications
Analysis of underivatised low volatility compounds by comprehensive two-dimensional gas chromatography with a short primary column
Publisher: Elsevier BV
Date: 02-2017
DOI: 10.1016/J.CHROMA.2017.08.069
Abstract: Comprehensive two-dimensional gas chromatography (GC×GC) approaches with cryogenic modulation were developed for the qualitative analysis of selected low volatility compounds in raw coffee bean extracts, without derivatisation. The approaches employed short first (
Comparative study of Eucalyptus dunnii volatile oil composition using retention indices and comprehensive two-dimensional gas chromatography coupled to time-of-flight and quadrupole mass spectrometry
Publisher: Elsevier BV
Date: 07-2008
DOI: 10.1016/J.CHROMA.2008.05.070
Abstract: In the present work, the composition of volatile oil from leaves of Eucalyptus dunnii was studied using comprehensive two-dimensional gas chromatography (GCxGC) techniques. Structurally related compounds were found to elute mainly in specific regions of the two-dimensional space, showing orderly distribution with chemical class. Mass spectra of essential oil components were obtained from two different mass spectrometry detection methods: quadrupole (qMS) and time-of-flight (TOFMS), using the same GCxGC system under the same chromatographic conditions. Higher values of Similarity (average S of 914 with TOFMS compared to 880 with qMS) and Reverse (average R of 944 with TOFMS compared to 881 with qMS) were obtained with GCxGC/TOFMS showing its superior performance, which was most likely due to better sensitivity and resolution arising from the TOFMS system, and lack of spectral bias. Also, the number of compounds found in E. dunnii essential oil was 15% higher when TOFMS was used. Most of these are lower abundance components or exhibit low quality mass spectra this supports the improved sensitivity obtained with TOFMS. A linear relationship (r2=0.998) between experimental retention indices (LTPRI) of 30 standard compounds obtained with GCxGC/TOFMS and GC with flame ionization detection literature retention indices is reported as an aid for compound identification.
Methods for generating second dimension retention index data in comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 11-2003
DOI: 10.1016/J.CHROMA.2003.09.006
Abstract: Two methods of generating transportable second dimension retention data are outlined for comprehensive two-dimensional gas chromatography (GC x GC). They are both refinements of a previously outlined procedure, which adapted 'isovolatile' curves to retention prediction maps developed in our laboratory, extended to a more polar homologous series, the linear primary alcohols. The earlier work investigated maps based on alkanes and methyl ketones and methyl esters here the method of data collection to generate the retention map has also changed, extending the retention base range. The resulting retention map permits a retention basis to be used for GC x GC data, however, a more polar retention set than alkanes is required. The calculation of 'retention indices' is aided by the generation of 'fractional reference compound' curves, by either direct manipulation of data local to the solute, or generation of a discrete curve coincident with the retention co-ordinates of the target compound.
Comparison of odor-active compounds in the spicy fraction of hop (Humulus lupulus L.) essential oil from four different varieties
Publisher: American Chemical Society (ACS)
Date: 23-12-4724
DOI: 10.1021/JF070739T
Abstract: The "spicy" character of hops is considered to be a desirable attribute in beer, associated with "noble hop aroma". However, the compounds responsible have yet to be adequately identified. Odorants in four s les of the spicy fraction of hop essential oil were characterized using gas chromatography-olfactometry (GC-O) and CharmAnalysis. Four hop varieties were compared, namely, Target, Saaz, Hallertauer Hersbrucker, and Cascade. Odor-active compounds were tentatively identified using comprehensive two-dimensional gas chromatography (GCxGC) combined with time-of-flight mass spectrometry (TOFMS). An intense "woody, cedarwood" odor was determined to be the most potent odorant in three of the four spicy fraction s les. This odor coincided with a complex region where between 8 and 13 compounds were coeluting in each of the four spicy fractions. The peak responsible was determined by (i) correlating peak areas with Charm values in eight hop s les and (ii) heart-cut multidimensional gas chromatography-olfactometry (MDGC-O). The compound responsible was tentatively identified as 14-hydroxy-beta-caryophyllene. Other important odorants identified were geraniol, linalool, beta-ionone, and eugenol.
Evaluation of Coptidis Rhizoma-Euodiae Fructus couple and Zuojin products based on HPLC fingerprint chromatogram and simultaneous determination of main bioactive constituents
Publisher: Informa UK Limited
Date: 12-08-2013
DOI: 10.3109/13880209.2013.793719
Abstract: Coptidis Rhizoma-Euodiae Fructus couple (CEC) is a classic traditional Chinese medicine preparation consisting of Coptidis Rhizoma and Euodiae Fructus at the ratio of 6:1, and used to treat gastro-intestinal disorders. Alkaloids are the main bioactive component. This research provides comprehensive analysis information for the quality control of CEC. To develop a high-performance liquid chromatography-diode array detection fingerprint for chemical composition characteristics of CEC and its products. The s les were separated with a Gemini C18 column by using gradient elution with water-formic acid (100:0.03) and acetonitrile as mobile phase. Flow rate was 1.0 mL/min and detection wavelength was 250 nm. Similarity analysis and principal component analysis (PCA) were employed to evaluate quality consistencies of analytes. Mean chromatograms and correlation coefficients of analytes were calculated by the software "Similarity Evaluation System for Chromatographic Fingerprint of Traditional Chinese Medicine". Fingerprint chromatogram comparison determined 20 representative general fingerprint peaks, and the fingerprint chromatogram resemblances are all better than 0.988. Consistent results were obtained to show that CEC and its related s les could be successfully ided into three groups. Contribution plots generated by PCA were performed to interpret differences among the s le groups while peaks which significantly contributed to classification were identified. Seven bioactive constituents in the s les were verified by quantitative analysis. The chromatographic fingerprint with similarity evaluation and PCA assay combined with quantification of seven compounds could be utilized as a quality control method for the herbal couple.
Retention time reproducibility in comprehensive two-dimensional gas chromatography using cryogenic modulation: II. An interlaboratory study
Publisher: Elsevier BV
Date: 11-2003
DOI: 10.1016/S0021-9673(03)00938-5
Abstract: An interlaboratory survey was conducted to determine the reproducibility of retention times in both the first (1D) and second dimension (2D) axes of the two-dimensional separation space, using the longitudinal cryogenic modulation comprehensive two-dimensional gas chromatographic approach. Intralaboratory reproducibility has been demonstrated in part 1 of this investigation [J. Chromatogr. A 968 (2002) 161]. Confidence in absolute retention times (hence component positions) in the two-dimensional separation space is critical to component identification. Comparing data from four independent laboratories, five independent gas chromatographs, five independent LMCS units, and numerous operators has determined that the LMCS cryogenic modulation approach provides reliable comprehensive two-dimensional GC results.
Headspace solid-phase microextraction combined with comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry for the determination of volatile compounds from marine salt
Publisher: Elsevier BV
Date: 08-2010
DOI: 10.1016/J.CHROMA.2010.06.050
Abstract: In this work, a methodology to characterise the volatile and semi-volatile compounds from marine salt by headspace solid-phase microextraction (HS-SPME) and comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GCxGC/TOFMS) was developed. S les from two saltpans of Aveiro, in Portugal, with erse locations, obtained over three years (2004, 2005, and 2007) were analysed. A 50/30microm inylbenzene/carboxen olydimethylsiloxane SPME fibre was used. The volatiles present in the headspace of the solid salt s les (crystals) were equilibrated overnight at 60 degrees C and extracted for 60min prior to injection in the GCxGC/TOFMS. 157 compounds, distributed over the chemical groups of hydrocarbons, aldehydes, esters, furans, haloalkanes, ketones, ethers, alcohols, terpenoids, C(13) norisoprenoids, and lactones were detected across the s les. Furans, haloalkanes and ethers were identified for the first time in marine salt. The large number of co-elutions on the first column that were resolved by the GCxGC system revealed the complexity of marine salt volatile composition. The existence of a structured 2D chromatographic behaviour according to volatility, in the first dimension ((1)D), and primarily polarity, in the second dimension ((2)D), was demonstrated, allowing more reliable identifications. The resolution and sensitivity of GCxGC/TOFMS enabled the separation and identification of a higher number of volatile compounds compared to GC-qMS, allowing a deeper characterisation of this natural product.
Comprehensive two-dimensional gas chromatography-mass spectrometry analysis of Pelargonium graveolens essential oil using rapid scanning quadrupole mass spectrometry
Publisher: Royal Society of Chemistry (RSC)
Date: 2003
DOI: 10.1039/B304371A
Cumulative solid phase microextraction sampling for gas chromatography-olfactometry of Shiraz wine
Publisher: Elsevier BV
Date: 09-2012
DOI: 10.1016/J.CHROMA.2012.03.084
Abstract: Solid phase microextraction (SPME) coupled to gas chromatography-olfactometry (GC-O) is now commonly used for determination of aroma-active compounds, but the method sensitivity and selectivity is restricted by the small volume and limited type of fibre coating phases. In an attempt to enhance the method performance, a cryogenic trapping (CT) approach was investigated in this study by coupling multiple SPME s ling events for wine headspace using GC-O analysis. By performing multiple SPME s ling employing different chemical polymer coatings, desorbed solute from the integrated s ling is accumulated by the CT at the front section of a Wax separation capillary column prior to chromatographic analysis. Results show that the CT was capable of retaining apolar alkane volatiles of decane and greater, and tested polar alcohols, including methanol. Chromatographic signals eluting later than the ethanol peak were found to progressively increase in response, and correlated well, with the cumulative number of SPME s lings. The approach was developed for GC-O screening of potent odorants in Shiraz wine collected from fibre coatings of polyacrylate (PA) and the triple-phase coated polydimethylsiloxane/ inylbenzene/carboxen (PDC). The aromagram for solute derived from a combined introduction of both PA plus PDC fibres (i.e. sequential fibre introduction into the injector termed as PADC) compared well to the sum of those s led by using a single fibre coating alone, which comprised of odorants derived from both fibre coatings. Accumulation in the CT of volatile solutes derived from up to 6 repeat PADC s ling events revealed a similar pattern of their aromagrams, though with stronger olfactory stimulus response. This study demonstrated a simple and effective way for enhancing SPME sensitivity and potentially less discrimination during the analysis of wine volatiles. However, the single dimensional GC separation method requires development of an improved separation strategy to better separate in idual compounds.
Principles and applications of comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 09-2002
Intake of total and added sugars and nutrient dilution in Australian children and adolescents
Publisher: Cambridge University Press (CUP)
Date: 28-09-2015
DOI: 10.1017/S0007114515003542
Abstract: This analysis aimed to examine the association between intake of sugars (total or added) and nutrient intake with data from a recent Australian national nutrition survey, the 2007 Australian National Children’s Nutrition and Physical Activity Survey (2007ANCNPAS). Data from participants ( n 4140 51 % male) who provided 2×plausible 24-h recalls were included in the analysis. The values on added sugars for foods were estimated using a previously published ten-step systematic methodology. Reported intakes of nutrients and foods defined in the 2007ANCNPAS were analysed by age- and sex-specific quintiles of %energy from added sugars (%EAS) or %energy from total sugars (%ETS) using ANCOVA. Linear trends across the quintiles were examined using multiple linear regression. Logistic regression analysis was used to calculate the OR of not meeting a specified nutrient reference values for Australia and New Zealand per unit in %EAS or %ETS. Analyses were adjusted for age, sex, BMI z -score and total energy intake. Small but significant negative associations were seen between %EAS and the intakes of most nutrient intakes (all P ·001). For %ETS the associations with nutrient intakes were inconsistent even then they were smaller than that for %EAS. In general, higher intakes of added sugars were associated with lower intakes of most nutrient-rich, ‘core’ food groups and higher intakes of energy-dense, nutrient-poor ‘extra’ foods. In conclusion, assessing intakes of added sugars may be a better approach for addressing issues of diet quality compared with intakes of total sugars.
Detector Technologies and Applications in Comprehensive Two-Dimensional Gas Chromatography
Publisher: Wiley
Date: 25-07-2011
Characterization of nitrogen-containing compounds in heavy gas oil petroleum fractions using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry
Publisher: American Chemical Society (ACS)
Date: 18-05-2010
DOI: 10.1021/EF1002364
Longitudinally Modulated Cryogenic System. A Generally Applicable Approach to Solute Trapping and Mobilization in Gas Chromatography
Publisher: American Chemical Society (ACS)
Date: 07-1997
DOI: 10.1021/AC961310W
Abstract: This paper describes a novel approach to solute trapping and remobilization. It involves the use of a subambient trap, with a narrow capillary column passing through the cooled region. A mechanism allows for longitudinal movement of the trap relative to the chromatographic column or narrow transfer line through which analytes travel. Either the trap or the column can be moved, and the frequency or manner of relative movement determines the type of result obtained. A series of preliminary studies are described that define the general approach to using this device and demonstrate the unique benefits that may arise from the modulation movement. Significant improvement (reduction) in peak width occurs if the device is placed immediately prior to the detection system, and consequently a great increase in detection limits results. With a 25 cm length of capillary column between the trap and detector, it is calculated that the plate height of dodecane is 0.082 mm, equivalent to 12 100 plates/m. This was found to be much greater than that for dodecane analyzed on a 25 m column. By slow displacement of the column through the trap, it is demonstrated that the solute is trapped in the first 1 cm (or less) of the column located in the cold trap.
A limitation of the Microtox® test for toxicity measurements of nonionic surfactants
Publisher: Wiley
Date: 07-1996
Investigation of folic acid stability in fortified instant noodles by use of capillary electrophoresis and reversed-phase high performance liquid chromatography
Publisher: Elsevier BV
Date: 12-2008
DOI: 10.1016/J.CHROMA.2008.09.098
Abstract: A single enzyme treatment with alpha-amylase, prior to the quantification of added folic acid (FA) in fortified instant fried Asian noodles with analysis performed by capillary zone electrophoresis (CZE) and reversed-phase high performance liquid chromatography (RP-HPLC) with UV detection, is described. The method was validated and optimized for capillary electrophoresis (CE) with separation achieved using a 8 mM phosphate-12 mM borate run buffer with 5% MeOH at pH 9.5. FA was well separated from matrix components with nicotinic acid (NA) employed as an internal standard. In a comparative study, separation of FA was performed using HPLC with a mobile phase consisting of 27% MeOH (v/v) in aqueous potassium phosphate buffer (3.5 mM KH(2)PO(4) and 3.2 mM K(2)HPO(4)), pH 8.5, and containing 5 mM tetrabutylammonium dihydrogen phosphate as an ion-pairing agent. For both methods, excellent results were obtained for various analytical parameters including linearity, accuracy and precision. The limit of detection was calculated to be 2.2 mg/L for CE without s le stacking and 0.10 mg/L with high performance liquid chromatography (HPLC). S le extraction involved homogenization and enzymatic extraction with alpha-amylase. Results indicated that FA was stable during four main stages of instant fried noodle manufacturing (dough crumbs, cut sheets, steaming and frying).
Combined effects of gamma-irradiation and modified atmosphere packaging on quality of some spices
Publisher: Elsevier BV
Date: 07-2014
DOI: 10.1016/J.FOODCHEM.2014.01.002
Abstract: Thyme (Thymus vidgaris L.), rosemary (Rosmarinus officinalis L.), black pepper (Piper nigrum L.) and cumin (Cuminum cyminum L.) in ground form were packaged in either air or 100% N2 and γ-irradiated at 3 different irradiation levels (7kGy, 12kGy, 17kGy). Total viable bacterial count, yeast and mould count, colour, essential oil yield and essential oil composition were determined. Microbial load was not detectable after 12kGy irradiation of all s les. Irradiation resulted in significant changes in colour values of rosemary and black pepper. The discolouration of the irradiated black pepper was lower in modified atmosphere packaging (MAP) compared to air packaging. Essential oil yield of irradiated black pepper and cumin was lower in air packaging compared to MAP. Gamma-irradiation generally decreased monoterpenes and increased oxygenated compounds, but the effect was lower in MAP. Overall, spices should be irradiated under an O2-free atmosphere to minimise quality deterioration.
Simple preparative gas chromatographic method for isolation of menthol and menthone from peppermint oil, with quantitative GC-MS and1H NMR assay
Publisher: Wiley
Date: 27-12-2012
Abstract: The quantitative performance of a simple home-built preparative gas chromatography (prep-GC) arrangement was tested, incorporating a micro-fluidic Deans switch, with collection of the target compound in a deactivated uncoated capillary tube. Repeat injections of a standard solution and peppermint s le were made into the prep-GC instrument. In idual compounds were eluted from the trapping capillary, and made up to constant volume. Chloronaphthalene internal standard was added in some cases. Recovered s les were quantitatively assayed by using GC-MS. Calibration linearity of GC-MS for menthol standard area response against number of injections (2-20 repeat injections) was excellent, giving R(2) of 0.996. For peppermint, menthol correlation over 2-20 repeated injections was 0.998 for menthol area ratio (versus IS) data. Menthone calibration for peppermint gave an R(2) of 0.972. (1) H NMR spectroscopy was conducted on both menthol and menthone. Good correspondence with reference spectra was obtained. About 80 μg of isolated menthol and menthone solute was collected over a sequence of 80 repeat injections from the peppermint s le, as assayed by 600 MHz (1) H NMR analysis (∼100% recovery for menthol from peppermint). A procedure is proposed for prediction of number of injections required to acquire sufficient material for NMR detection.
Untargeted profiling of Glycyrrhiza glabra extract with comprehensive two-dimensional liquid chromatography-mass spectrometry using multi-segmented shift gradients in the second dimension: Expanding the metabolic coverage
Publisher: Wiley
Date: 27-02-2018
Abstract: Metabolic profiling of Glycyrrhiza glabra using comprehensive two-dimensional liquid chromatography (LC × LC) coupled with photodiode array (PDA) and mass spectrometry (MS) detection is described. The separation was conducted under reversed-phase conditions, using a combination of first dimension (
Spectroscopic analysis of heterogeneous photocatalysis products of nonylphenol- and primary alcohol ethoxylate nonionic surfactants
Publisher: Elsevier BV
Date: 11-1996
Group-Type Analysis of Hydrocarbons and Sulfur Compounds in Thermally Stressed Merox Jet Fuel Samples
Publisher: American Chemical Society (ACS)
Date: 21-08-2017
DEtermination of trace levels of diazinon and propetamphos in water and sewage by solid phase extraction
Publisher: Informa UK Limited
Date: 1994
Positional and geometric isomer separation of FAME by comprehensive 2-D GC
Publisher: Wiley
Date: 07-2200
DOI: 10.1007/S11745-002-0953-8
Abstract: The technique of comprehensive GC (GC x GC) was applied to the analysis of a standard mixture of FAME. The methodology involved the use of two directly coupled capillary GC columns providing different retention mechanisms, with a pulsing modulator located near their union. The first column was chosen to elute analytes based on b.p. variations, and the second column was based on polarity. Thus, the separation in the two dimensions was orthogonal, since solutes delivered simultaneously to the second column had similar b.p., and the second column separated these primarily on their differentiating mechanisms of polarity. Greater sensitivity of detection and narrower peak widths were obtained here, peak response increases of about 20-fold were obtained, with pulsed peak widths of about 150 ms. Peaks were displayed in a 2-D contour plot to allow the complexity of the compounds to be seen and their b.p. and polarity properties to be readily recognized. Chromatographic separation of geometric and positional isomers of FAME in the 2-D space is possible. Since retention can be related to the degree and manner of unsaturation and isomerization, and as peak positions are highly reproducible in the 2-D retention map, this is a useful aid for component identification in the absence of appropriate standards. In this work, two column combinations were used to examine the effects of polarity changes on component separation. Improved quantitation based on FID area measurement was demonstrated. A s le of marine oil gave 49 resolved, identified peaks, with at least an additional 20 peaks resolved but not identified.
Comprehensive two-dimensional gas chromatography with flame photometric detection applied to organophosphorus pesticides in food matrices
Publisher: Elsevier BV
Date: 07-2013
Qualitative mass spectrometric analysis of the volatile fraction of creosote-treated railway wood sleepers by using comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 2008
DOI: 10.1016/J.CHROMA.2007.11.069
Abstract: The volatile composition of 20-year-old out-of-service creosote-treated railway wood sleepers was studied. The emitted volatile fraction was collected by means of dynamic purge-and-trap concentration at ambient temperature, and analyzed by comprehensive two-dimensional gas chromatography (GC x GC) hyphenated with mass spectrometric detection systems, using quadrupole (GC x GC/qMS) and time-of-flight (GC x GC/ToF-MS) mass analyzers and selective nitrogen-phosphorus detection (GC x GC-NPD). The analysis of mass spectrometry data and GC x GC retention time allowed the tentative identification of about 300 compounds based on spectrometric data and positioning of each compound in the GC x GC plot. Major important headspace components are polyaromatic hydrocarbons, phenols and benzene derivatives, hydrocarbons and heterocyclic compounds containing nitrogen, sulphur or oxygen atoms. Many of the reported compounds are listed as belonging to toxicological substance classes which have been related to harmful health effects. GC x GC provides greater speciation and evidence of composition heterogenicity of the s le than one-dimensional GC analysis, thus allowing to better demonstrate its potential toxicity. Data obtained by specific detection systems for N-heterocycles assisted mass data interpretation assignments. The enhanced separation power obtained after GC x GC compared to one-dimensional gas chromatography (1D-GC) together with spectral deconvolution and correlation with physical-chemical data, allowed the identification of complex isomer clusters, as demonstrated for alkylquinolines, and applied also to alkylphenols, alkylbenzenes and alkylnaphthalenes.
The detection of adult cortical auditory evoked potentials (CAEPs) using an automated statistic and visual detection
Publisher: Informa UK Limited
Date: 2009
DOI: 10.3109/14992020903140928
Abstract: The detection of adult cortical auditory evoked potentials (CAEPs) can be challenging when the stimulus is just audible. The effectiveness of a statistic compared with expert examiners in (1) detecting the presence of CAEPs when stimuli were present, and (2) reporting the absence of CAEPs when no stimuli were present, was investigated. CAEPs recorded from ten adults, using two speech-based stimuli, five stimulus presentation levels, and non-stimulus conditions, were given to four experienced examiners who were asked to determine if responses to auditory stimulation could be observed, and their degree of certainty in making their decision. These recordings were also converted to multiple dependent variables and Hotelling's T2 was applied to calculate the probability that the mean value of any linear combination of these variables was significantly different from zero. Results showed that Hotelling's T2 was equally sensitive to the best of in idual experienced examiners in differentiating a CAEP from random noise. It is reasonable to assume that the difference in response detection for a novice examiner and Hotelling's T2 would be even greater.
Solid-phase microextraction - On-fibre derivatization with comprehensive two dimensional gas chromatography analysis of trans-resveratrol in wine
Publisher: Springer Science and Business Media LLC
Date: 2003
DOI: 10.1007/BF02492127
Comprehensive two-dimensional gas chromatography with mass spectrometry: an advanced bioanalytical technique for clinical metabolomics studies
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2AN00584K
Abstract: This review highlights the current state of knowledge in the development of GC × GC-MS for the analysis of clinical metabolites. Selected applications are described as well as our perspectives on current challenges and potential future directions.
In-tube solid phase micro-extraction-gas chromatography of volatile compounds in aqueous solution
Publisher: Royal Society of Chemistry (RSC)
Date: 1999
DOI: 10.1039/A902567G
Development of a new compact high resolution sector inductively coupled plasma mass spectrometer
Publisher: Royal Society of Chemistry (RSC)
Date: 1998
DOI: 10.1039/A800331I
Determination of selected emerging contaminants in freshwater invertebrates using a universal extraction technique and liquid chromatography accurate mass spectrometry
Publisher: Wiley
Date: 04-09-2018
Abstract: A simple s le preparation method based on a modified liquid-phase extraction approach to extract selected pharmaceuticals and personal care products from freshwater organisms is described. Extracted s les were analysed using liquid chromatography with Q-Exactive plus hybrid quadrupole Orbitrap mass spectrometry, using 2.6 μm C18 media. A 0.1% v/v acetic acid/acetonitrile mobile phase was applied over a 20 min gradient. Method detection limits in full scan mode were ca. 0.04-2.38 ng of analyte per g of s le. Linearity ranged from 0.9750 to 0.9996 over the calibration range of 0.01-100 μg/L MS mass accuracy was <2 ppm for most analytes. This method was applied to quantify six pharmaceuticals and personal care products in seven invertebrate s les. For tandem mass spectrometry analysis, selection of precursor ions was performed for each pharmaceutical, with Mass Frontier software illustrating the fragmentation mechanism. Effects of collision energy on intensities of ions was further investigated. The tandem mass spectrometry condition resulting in the highest signal of respective selected product ion was selected to confirm each pharmaceutical, which was initially observed in the full scan mode. Results indicate that pharmaceuticals and personal care products found to be present in water-ways, may be incorporated into organisms that live in the environment of affected water streams.
Direct ionic liquid extractant injection for volatile chemical analysis – A gas chromatography sampling technique†
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4GC01364F
Abstract: Direct GC injection of analytes in IL using a PTV injector retained IL extractant in the injector, with analytes quantitatively transferred to the column.
Identification of character-impact odorants in coriander and wild coriander leaves using gas chromatography-olfactometry (GCO) and comprehensive two-dimensional gas chromatography-time-of-flight mass spectometry (GC x GC-TOFMS)
Publisher: Wiley
Date: 06-2005
Abstract: The essential oil of coriander leaves ( Coriandrum sativum ) and wild coriander leaves ( Eryngium foetidum ) grown in Fiji was obtained by steam distillation. The aroma profiles were characterised using gas chromatography‐olfactometry (GCO) and CharmAnalysis TM . The character‐impact odorants were identified using comprehensive two‐dimensional gas chromatography (GC×GC) combined with time‐of‐flight mass spectrometry (TOFMS). During GCO analysis, the co‐elution of E ‐2‐alkenals and E ‐2‐alken‐1‐ols resulted in the perception of ‘odour‐clusters’. The most important odorants in C. sativum were found to be Z‐ 2‐decenal, a co‐eluting odour‐cluster ( E ‐2‐dodecenal, E ‐2‐dodecen‐1‐ol, and 1‐dodecanol), β‐ionone, eugenol, and E ‐2‐decenal. E ‐2‐Decen‐1‐ol was the most abundant compound in C. sativum (26.0% TIC) but only contributed 0.39% of the total odour activity. The most abundant compound in E. foetidum was E‐ 2‐dodecenal (63.5% TIC), which also contributed the most odour activity (52.9%). Other important odorants were either eugenol or a trimethylbenzaldehyde isomer, β‐ionone, Z‐ 4‐dodecenal, dodecanal, and E‐ 2‐tetradecenal. GC×GC–TOFMS allowed the identification of 42 and 20 compounds not previously reported in the literature for C. sativum and E. foetidum , respectively. In particular, β‐ionone was determined to be an important odorant in both s les but could not be identified with GC–qMS.
Review of the role and methodology of high resolution approaches in aroma analysis
Publisher: Elsevier BV
Date: 2015
DOI: 10.1016/J.ACA.2014.06.029
Abstract: Analysis of the odour complexity in food and beverage products demands high resolution approaches for distinguishing in idual aroma-impact compound(s), and for assessing their contribution to the global aroma of a s le. This paper aims to review current applications incorporating different advanced separation methodologies, and their roles in achieving high resolution aroma analysis. This includes prior low resolution gas chromatography-olfactometry (GC-O) with fractionation procedures using chemical manipulation, adsorption chromatography and ion exchange separation. Innovative multidimensional gas chromatography (MDGC) arrangements that are appropriately designed with olfactometry are of specific focus here. The revelation of resolved components using these integrated approaches provides significantly improved knowledge of aroma composition in s les.
Comparative qualitative analysis of nonylphenol isomers by gas chromatography-mass spectrometry combined with chemometric resolution
Publisher: Elsevier BV
Date: 12-2010
DOI: 10.1016/J.CHROMA.2010.10.024
Abstract: The relationship between nonylphenol (NP) isomers' structures and their estrogenic potencies has been evaluated previously. However, due to their similarities in both chemical and physical properties, complete separation and identification remain strikingly difficult. In the present study, gas chromatography-mass spectrometry (GC-MS) is employed to separate commercial NP isomers. Both extracted ion chromatograms (EIC) based on selected ions known to be definitive for the suite of isomers, and the heuristic evolving latent projection (HELP) chemometric resolution method have been applied for the analysis and identification of the NP isomers. This method corrected the wrong identification of one isomer which was suspected based on the EIC data, and also was able to be applied for the determination of an additional isomer with low abundance. Overall, 15 NP isomers have been proposed by the HELP interpretation method. Pure component chromatograms and mass spectra have been extracted with the aid of chemometric resolution. The applicability of the commercial deconvolution software package automated mass spectral deconvolution and identification system (AMDIS) has also been tested against the HELP method for comparative presentation of pure component mass spectra.
Determination of polycyclic aromatic hydrocarbons in vegetable oils using solid-phase microextraction-comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry
Publisher: Elsevier BV
Date: 08-2007
DOI: 10.1016/J.CHROMA.2007.05.105
Abstract: A simple and fast solid-phase microextraction method coupled with comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry was developed for analysis of polycyclic aromatic hydrocarbons in edible oil, performed directly in a hexane solution of the oil. S ling conditions (solvent used, extraction time, extraction temperature and fiber rinsing time) were optimized by using a s le of oil fortified with a standard solution of polycyclic aromatic hydrocarbons. The method was validated by calculating linear range, correlation coefficient, accuracy, repeatability, detection limit and quantification limit. The method was applied to several oils collected from the market and directly from an olive pomace extraction plant.
Comprehensive Two-Dimensional Gas Chromatography Advances in Technology and Applications: Biennial Update
Publisher: American Chemical Society (ACS)
Date: 18-12-2020
Multi-column trajectory to advanced methods in comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 09-2018
Cassia alata (Linnaeus) Roxburgh for Skin: Natural Remedies for Atopic Dermatitis in Asia and Their Pharmacological Activities
Publisher: MDPI AG
Date: 26-12-2022
DOI: 10.3390/COSMETICS10010005
Abstract: Atopic dermatitis (AD) is an inflamed skin condition with relapsing pruritus and cutaneous physiological dysfunction. This skin disorder is widespread around the world and frequently affects infants, children and adults. Natural products with bioactive lead compounds are the source of natural medicines for complementary and alternative therapy in managing AD. Cassia alata has been used traditionally as a remedy for a variety of health issues. In Asian countries, it is used as an ethnomedicine to treat skin conditions such pityriasis versicolor, ringworm, scabies, shingles, urticaria and itching. According to previously published studies, the phytochemicals in C. alata may have a wide range of significant pharmacological effects. AD management is highlighted here, as this review explores the literature on the pharmacological effects of C. alata and its phytochemical content. Specifically, antibacterial, wound healing, anti-inflammatory and antioxidant effects are reviewed and discussed in relation to AD management.
Observation and explanation of two-dimensional interconversion of oximes with multiple heart-cutting using comprehensive multidimensional gas chromatography
Publisher: Elsevier BV
Date: 04-2018
DOI: 10.1016/J.CHROMA.2018.02.035
Abstract: Real-time interconversion processes produce unconventional peak broadening in gas chromatography (GC), and can be used to generate kinetic and thermodynamic data. In this study, an unusual separation situation in comprehensive two dimensional GC where two dimensional interconversion (i.e. a raised plateau in both first and second dimension,
Separation of zinc dialkyldithiophosphates in lubricating oil additives by normal-phase high-performance liquid chromatography
Publisher: Elsevier BV
Date: 10-1996
Optimisation of sulphur emission in molecular emission cavity analysis. Effects of variation in cavity position and phosphate addition
Publisher: Elsevier BV
Date: 12-1980
Teaching Analytical Instrumentation Through Remote Access – A Gas Chromatography Perspective
Publisher: American Chemical Society (ACS)
Date: 09-02-2023
Amino acid analysis by using comprehensive two-dimensional gas chromatography
Publisher: Springer Science and Business Media LLC
Date: 19-04-2005
DOI: 10.1007/S00216-005-3083-X
Abstract: The separation characteristics of alkylchloroformate-derivatised amino acids (AAs) by using comprehensive two-dimensional gas chromatography (GCxGC) is reported. The use of a low-polarity olar column set did not provide as good a separation performance as that achieved with a polar/non-polar column set, where the latter appeared to provide less correlation over the separation space. The degree of component correlation in each column set was estimated by using the correlation coefficient (r(2) for (1)t(R) and (2)t(R) data) with the low-polarity olar and polar/low-polarity sets returning correlation coefficients of 0.86, and 0.00 respectively, under the respective conditions employed for the experiments. The 1.5-m non-polar (2)D column (0.1-mm ID 0.1-mum film thickness) gave peak halfwidths of the order of 50-80 ms. Linearity of detection was good, over a three order of magnitude concentration range, with typical lower detection limit of ca. 0.01 mg L(-1), compared with 0.5 mg L(-1) for normal GC operation with splitless injection. The method was demonstrated for analysis of AAs in a range of food and beverage products, including wine, beer and honey. The major AA in these s les was proline. The Heineken beer s le had a relatively more complex and more abundant AA content compared with the other beer s le. The wine and honey s les also gave a range of AA compounds. Repetition of the s le preparation/analysis procedure for the honey s le gave acceptable reproducibility for in idual AAs.
Internal electrolyte temperatures for polymer and fused-silica capillaries used in capillary electrophoresis
Publisher: Wiley
Date: 11-2005
Abstract: Polymers are important as materials for manufacturing microfluidic devices for electrodriven separations, in which Joule heating is an unavoidable phenomenon. Heating effects were investigated in polymer capillaries using a CE setup. This study is the first step toward the longer-term objective of the study of heating effects occurring in polymeric microfluidic devices. The thermal conductivity of polymers is much smaller than that of fused silica (FS), resulting in less efficient dissipation of heat in polymeric capillaries. This study used conductance measurements as a temperature probe to determine the mean electrolyte temperatures in CE capillaries of different materials. Values for mean electrolyte temperatures in capillaries made of New Generation FluoroPolymer (NGFP), poly-(methylmethacrylate) (PMMA), and poly(ether ether ketone) (PEEK) capillaries were compared with those obtained for FS capillaries. Extrapolation of plots of conductance versus power per unit length (P/L) to zero power was used to obtain conductance values free of Joule heating effects. The ratio of the measured conductance values at different power levels to the conductance at zero power was used to determine the mean temperature of the electrolyte. For each type of capillary material, it was found that the average increase in the mean temperature of the electrolyte (DeltaT(Mean)) was directly proportional to P/L and inversely proportional to the thermal conductivity (lambda) of the capillary material. At 7.5 W/m, values for DeltaT(Mean) for NGFP, PMMA, and PEEK were determined to be 36.6, 33.8, and 30.7 degrees C, respectively. Under identical conditions, DeltaT(Mean) for FS capillaries was 20.4 degrees C.
Average theoretical peak time as a metric to analytical speed in one dimensional and multidimensional gas chromatographic separations
Publisher: Elsevier BV
Date: 03-2022
DOI: 10.1016/J.CHROMA.2022.462887
Abstract: The definition of a chromatographic analysis speed based simply on analysis time is an outdated concept to define conventional chromatography, fast chromatography, and emerging high-resolution techniques such as comprehensive two-dimensional and comprehensive three-dimensional gas chromatography. Here, the metric average theoretical peak time (ATPT) is proposed for separation speed, considering conventional and multidimensional separations. ATPT can be defined as the time (in ms per peak) needed to elute a theoretical peak in a chromatographic system. Using this metric, it is possible to define ranges, proposed for a normal speed (ATPT higher than 4000 ms eak), high speed (ATPT range from 600 to 4000 ms eak), very high speed (ATPT range from 200 to 600 ms eak), hyper speed (ATPT range from 3.3 to 200 ms eak) and ultra high speed chromatography (ATPT lower than 3.3 ms eak), that combines time and efficiency metrics. This metric was applied in several contexts to demonstrate its robustness to evaluate chromatographic separations for different techniques and analytical conditions. Applications also demonstrate the advantages of the use of ATPT as a method development metric tool.
Gas chromatography of some metal dialkyldithiophosphates with packed and capillary columns using flame photometric detection
Publisher: Elsevier BV
Date: 1982
Molecular interconversion behaviour in comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 06-2022
DOI: 10.1016/J.CHROMA.2004.01.035
Abstract: Comprehensive two-dimensional gas chromatography (GC x GC) is shown to provide information on dynamic molecular behaviour (interconversion), with the interconversion process occurring on both columns in the coupled-column experiment. The experiment requires suitable adjustment of both experimental conditions and relative dimensions of each of the columns. In this case, a longer column than normally employed in GC x GC allows sufficient retention duration on the second column, which permits the typical plateau-shape recognised for the interconversion process to be observed. The extent of interconversion depends on prevailing temperature, retention time, and the phase type. Polyethylene glycol-based phases were found to result in high interconversion kinetics, although terephthalic acid-terminated polyethylene glycol had a lesser extent of interconversion. Much less interconversion was seen for phenyl-methylpolysiloxane and cyclodextrin phases. This suggests that for the oximes, interconversion largely occurs in the stationary phase. Ex les of different extents of interconversion in both dimensions are shown, including peak coalescence on the first column with little interconversion on the second column.
Detection of Volatiles from Raw Beef Meat from Different Packaging Systems Using Solid-Phase Microextraction GC–Accurate Mass Spectrometry
Publisher: MDPI AG
Date: 27-08-2021
Abstract: The volatile profile of raw beef contains vital information related to meat quality and freshness. This qualitative study examines the effect of packaging system on the formation and release of volatile organic compounds (VOCs) from raw beef over time, relative to the packaging best before date (BBD). The three packaging systems investigated were modified atmospheric packaging, vacuum packaging, and cling-wrapped packaging. Porterhouse steak s les with the same BBD were analysed from 3 days before to 3 days after the BBD. VOCs were detected via preconcentration using solid-phase microextraction combined with gas chromatography–accurate mass quadrupole time-of-flight mass spectrometry. In total, 35 different VOCs were tentatively identified. Interestingly, there was no clear relationship of the VOCs detected between the three packaging systems, with only carbon disulphide and acetoin, both known volatiles of beef, detected in all three. This is the first study to investigate the effects of commercial packaging systems on VOC formation it provides an understanding of the relationship of VOCs to the BBD that is essential for the development of on-pack freshness and quality sensors.
Addressing the Challenges to Identification in Gas Chromatography by Increased Resolution and Enhanced Detection Modalities
Publisher: Wiley
Date: 05-07-2018
Abstract: In the past 15+ years, gas chromatography (GC) has undergone a renaissance in its implementation on the basis of the "disruptive" technology of comprehensive two-dimensional gas chromatography (GC×GC). With a foundation based upon a two-column GC separation approach, GC×GC significantly alters the classical multidimensional gas chromatography (MDGC) method by employing very fast separation on a second dimension (
Concepts, selectivity options and experimental design approaches in multidimensional and comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 09-2020
Novel hybrid comprehensive 2D - Multidimensional gas chromatography for precise, high-resolution characterization of multicomponent samples
Publisher: American Chemical Society (ACS)
Date: 05-06-2012
DOI: 10.1021/AC300429Y
Abstract: A novel hybrid (sequential) comprehensive 2D-multidimensional gas chromatography (GC × GC-MDGC) method for complex s le manipulation and separation is described. It incorporates a separation step that approximates slow modulation GC × GC, prior to microfluidic Deans switch heart-cutting of a targeted region(s) into a third analytical column. It allows discrete single or multiple components, bands or regions, or any combination of these to be selected and excised from within the 2D GC × GC separation space. The excised in idual components can be further collected and studied. Alternatively, any unresolved or poorly resolved components, or regions that require further separation, can be transferred to an additional (third) column separation step. The method is applied to separation and quantitative analysis of oxygenates in a thermally stressed algae-derived biofuel oil by using flame ionization detection (FID), without any prefractionation. This permits oxygenated compounds to be fully resolved from saturated (matrix) compounds, which are completely excluded from the third column. Improved separation was obtained between target classes (aldehydes, 2-ketones, alcohols, acids). Excellent calibration linearity, and retention time and peak area reproducibility were obtained for 14 oxy-compounds present in trace amount in the complex biofuel matrix. Accuracy of microfluidic transfer to the third column, and the profile reproducibility before and after heart-cut operations, was demonstrated by extracting single components from a complex coffee volatile s le.
Selectivity differences of coordination compound stationary phases for polyaromatic hydrocarbons and polar analytes in gas and liquid phases
Publisher: Elsevier BV
Date: 06-2017
DOI: 10.1016/J.CHROMA.2017.04.037
Abstract: A precursor solution to the metal-organic framework (MOF), Cd(1,4,7,10-tetrakis(4-carboxybenzyl)-1,4,7,10-tetraazacyclododecane), was aged in a surface-functionalised 250μm-diameter capillary, to generate a film containing the constituents of the bulk phase crystalline material. EDX analysis revealed a higher ratio of ligand elements (C, N and O) to Cd in the capillary coated phase compared to that achieved from bulk synthesis in a vial. Separation performance of the coated capillary for gas chromatography (GC) was compared to the performance of the original MOF crystals packed in tips for liquid elution chromatography (LEC) towards the separation of polycyclic aromatic hydrocarbons (PAHs) and small probe analytes with different properties. This study showed that different retention mechanisms were observed for the same set of analytes in gas and liquid phases. Independently of the trend of vapour pressure difference, the GC result showed less specific size selective retention, but with stronger retention towards larger PAHs. A linear solvation energy relationship correlation further revealed enhanced retention contributions (positive stationary phase descriptor values) by cavity formation/dispersion interactions and H-bonding with acid functionality of the probe analytes in both GC and LEC (though stronger in LEC), whilst H-bonding with basic functional groups slightly increased retention in GC retention was strengthened by dipole-dipole/dipole-induced dipole interactions only in LEC.
Dietary docosahexaenoic acid supplementation enhances expression of fatty acid-binding protein 5 at the blood–brain barrier and brain docosahexaenoic acid levels
Publisher: Wiley
Date: 07-2018
DOI: 10.1111/JNC.14342
Abstract: The cytoplasmic trafficking of docosahexaenoic acid (DHA), a cognitively beneficial fatty acid, across the blood-brain barrier (BBB) is governed by fatty acid-binding protein 5 (FABP5). Lower levels of brain DHA have been observed in Alzheimer's disease (AD), which is associated with diminished BBB expression of FABP5. Therefore, up-regulating FABP5 expression at the BBB may be a novel approach for enhancing BBB transport of DHA in AD. DHA supplementation has been shown to be beneficial in various mouse models of AD, and therefore, the aim of this study was to determine whether DHA has the potential to up-regulate the BBB expression of FABP5, thereby enhancing its own uptake into the brain. Treating human brain microvascular brain endothelial (hCMEC/D3) cells with the maximum tolerable concentration of DHA (12.5 μM) for 72 h resulted in a 1.4-fold increase in FABP5 protein expression. Associated with this was increased expression of fatty acid transport proteins 1 and 4. To study the impact of dietary DHA supplementation, 6- to 8-week-old C57BL/6 mice were fed with a control diet or a DHA-enriched diet for 21 days. Brain microvascular FABP5 protein expression was up-regulated 1.7-fold in mice fed the DHA-enriched diet, and this was associated with increased brain DHA levels (1.3-fold). Despite an increase in brain DHA levels, reduced BBB transport of
Chemical characterisation of two Australian-grown strawberry varieties by using comprehensive two-dimensional gas chromatography-mass spectrometry
Publisher: Elsevier BV
Date: 12-2021
DOI: 10.1016/J.FOODCHEM.2013.05.083
Abstract: The volatile compositions of two strawberry varieties ('Albion' and 'Juliette') grown in Australia were analysed with comprehensive two-dimensional gas chromatography (GC×GC) combined with time-of-flight mass spectrometry (ToFMS). A suitable data processing method was created that should be sufficiently robust to compare s le chromatograms within a harvest season as well as between seasons with relative ease. Ninety-four compounds were tentatively or positively identified between the two varieties of which 20 have apparently not been previously reported to be components of strawberry volatiles. It was determined that Albion and Juliette have comparable total soluble solids content close to 11°Brix. However, since Juliette exhibited a lower titratable acidity content than Albion, it consequently has a slightly larger sugar/acid ratio. The presence of 2,5-dimethyl-4-hydroxy-(2H)-furan-3-one (furaneol) was detected only in Juliette and this variety also had a higher area percentage of 2,5-dimethyl-4-methoxy-(2H)-furan-3-one (mesifuran), according to the s ling protocol. These experimental results offer possible explanations as to why Juliette is perceived to have a sweeter flavour than Albion.
Pesticides Analysis: Advantages of Increased Dimensionality in Gas Chromatography and Mass Spectrometry
Publisher: Informa UK Limited
Date: 03-02-2015
Cyclodextrin metal-organic framework-polymer composite membranes towards ultimate and stable enantioselectivity
Publisher: Elsevier BV
Date: 02-2021
Microwave assisted synthesis of the fragrant compound Calone 1951®
Publisher: Elsevier BV
Date: 2005
Can wine quality be predicted by small volatile compounds? A study based on performance of wine show entries and their volatile profiles
Publisher: Wiley
Date: 18-09-2022
DOI: 10.1002/FFJ.3720
Abstract: It is widely recognized that wine aroma critically influences wine quality, yet the extent to which volatile compound composition in wine determines wine quality has proven difficult to define, beyond the negative influence of taint compounds. While some relationships between concentration of volatile aroma compounds and wine quality have been made, this has been usually based on single molecules, in laboratory wines and without reference to experienced wine panels. Here, we collected and analysed 157 commercial Shiraz wines from a competitive show over 2 years. We found significant ( P .05) correlations between specific volatiles and the panel's wine quality scores. However, these correlations were not always consistent between years. We could not explain medals given to wine entries solely based on multivariate analysis of their composite volatile composition. Here, we suggest that aroma determination in judging wine quality does not completely explain the assessment of wine, and appearance (colour, clarity) and taste may be more influential factors. There are considerable practical difficulties in establishing a convincing wine quality prediction model based on analysis of volatile compounds alone.
Nest- and colony-mate recognition in polydomous colonies of meat ants (Iridomyrmex purpureus)
Publisher: Springer Science and Business Media LLC
Date: 23-03-2006
DOI: 10.1007/S00114-006-0109-Y
Abstract: Workers of polydomous colonies of social insects must recognize not only colony-mates residing in the same nest but also those living in other nests. We investigated the impact of a decentralized colony structure on colony- and nestmate recognition in the polydomous Australian meat ant (Iridomyrmex purpureus). Field experiments showed that ants of colonies with many nests were less aggressive toward alien conspecifics than those of colonies with few nests. In addition, while meat ants were almost never aggressive toward nestmates, they were frequently aggressive when confronted with an in idual from a different nest within the same colony. Our chemical analysis of the cuticular hydrocarbons of workers using a novel comprehensive two-dimensional gas chromatography technique that increases the number of quantifiable compounds revealed both colony- and nest-specific patterns. Combined, these data indicate an incomplete transfer of colony odor between the nests of polydomous meat ant colonies.
Metabolism in anoxic permeable sediments is dominated by eukaryotic dark fermentation
Publisher: Springer Science and Business Media LLC
Date: 28-11-2017
DOI: 10.1038/NGEO2843
Integrated multidimensional and comprehensive 2D GC analysis of fatty acid methyl esters
Publisher: Wiley
Date: 02-2013
Abstract: Fatty acid methyl ester (FAME) profiling in complex fish oil and milk fat s les was studied using integrated comprehensive 2D GC (GC × GC) and multidimensional GC (MDGC). Using GC × GC, FAME compounds--cis- and trans-isomers, and essential fatty acid isomers--ranging from C18 to C22 in fish oil and C18 in milk fat were clearly displayed in contour plot format according to structural properties and patterns, further identified based on authentic standards. Incompletely resolved regions were subjected to MDGC, with Cn (n = 18, 20) zones transferred to a (2)D column. Elution behavior of C18 FAME on various (2)D column phases (ionic liquids IL111, IL100, IL76, and modified PEG) was evaluated. In idual isolated Cn zones demonstrated about four-fold increased peak capacities. The IL100 provided superior separation, good peak shape, and utilization of elution space. For milk fat-derived FAME, the (2)D chromatogram revealed at least three peaks corresponding to C18:1, more than six peaks for cis/trans-C18:2 isomers, and two peaks for C18:3. More than 17 peaks were obtained for the C20 region of fish oil-derived FAMEs using MDGC, compared with ten peaks using GC × GC. The MDGC strategy is useful for improved FAME isomer separation and confirmation.
Targeted multidimensional gas chromatography for the quantitative analysis of suspected allergens in fragrance products
Publisher: Elsevier BV
Date: 10-2006
DOI: 10.1016/J.CHROMA.2006.08.012
Abstract: Two approaches are described and compared for the analysis of suspected allergens (SAs) in fragrance products, which are defined by the Scientific Committee of Cosmetics and Non-Food Products (SCCNFP). The first consists of a comprehensive two-dimensional gas chromatography (GC x GC) experiment using both a "conventional" non-polar olar column combination and an "inverse" polar/non-polar column set. The second approach uses a targeted multidimensional gas chromatography (MDGC) system employing a Deans type pneumatic switch and a longitudinally modulated cryogenic system (LMCS). It was found that the conventional and inverse column sets complement each other well, providing identification of SAs present. Compounds well retained on the second dimension of one column set were the first to be eluted from the other. In some instances SAs co-eluting with matrix components on the second dimension for a given column set were clearly resolved on the other, although this has the disadvantage of requiring two analytical runs. Targeted MDGC with a non-polar olar column set, successfully separated all SAs identified within a fragrance product. The instrument is set up in a similar fashion to a GC x GC system though with longer second dimension ((2)D) column, a cryogenic trap at the beginning of the second column, and a pneumatic switch coupling both columns. The data are easier to process than for a GC x GC experiment. The targeted MDGC method has the capacity to deliver far greater efficiency to targeted regions of a primary separation than a GC x GC experiment, whilst still maintaining overall run times similar to those of a conventional one-dimensional (1D) GC experiment. Cryogenic focussing at the beginning of the (2)D column delivers enhanced sensitivity, accurate (2)D retention times and narrow peak widths these are responsible for an increased resolution obtained from the fast, relatively short (approximately 5 m) (2)D column. The two column set GC x GC analysis provided a quick and effective means to qualitatively determine the presence of six SAs in a commercially available air freshener, however all were not adequately resolved from matrix components. In contrast, quantitation was straightforward using the targeted MDGC method.
Profiling of soil fatty acids using comprehensive two-dimensional gas chromatography with mass spectrometry detection
Publisher: Elsevier BV
Date: 11-2013
DOI: 10.1016/J.CHROMA.2013.08.095
Abstract: Profiling of phospholipid fatty acids (PLFA) represents a challenging goal for distinguishing the ersity of microbial communities and biomass in the complex and heterogeneous soil ecosystem. Comprehensive two-dimensional gas chromatography (GC×GC) coupled with simultaneous flame ionisation and mass spectrometry detection was applied as a culture-independent method for PLFA profiling of microbial classification in forest soil. A number of column sets were evaluated for the GC×GC separation of fatty acid methyl esters (FAME). Due to better isomeric separation and compound patterns on the 2D contour plot, an apolar-polar column combination was selected for soil microbial PLFA characterisation. A comprehensive view of PLFA composition with carbon chain length varying from 12 to 20 was observed in forest soil s les, with the commonly reported bacterial FAME of iso-/anteiso-, methyl-branched-, cyclopropyl-, and hydroxyl-substituted FA identified by their mass spectral and retention time according to authentic standards. Notably, some uncommon oxygenated FAME were found in high abundance and were further characterised by GC×GC coupled with high resolution mass spectrometry. This tentatively revealed geometric pairs of methyl 9,10-epoxyoctadecanoate isomers.
Comparison of column phase configurations for comprehensive two dimensional gas chromatographic analysis of crude oil and bitumen
Publisher: Elsevier BV
Date: 09-2006
A larger pool of ozone-forming carbon compounds in urban atmospheres
Publisher: Springer Science and Business Media LLC
Date: 06-2000
DOI: 10.1038/35015540
Abstract: Volatile organic compounds play a central role in the processes that generate both urban photochemical smog and tropospheric ozone. For successful and accurate prediction of these pollution episodes, identification of the dominant reactive species within the volatile organic carbon pool is needed. At present, lack of resolution inherent in single-column chromatographic analysis limits such a detailed chemical characterization of the complex urban atmosphere. Here we present an improved method of peak deconvolution from double-column (orthogonal) gas chromatography. This has enabled us to isolate and classify more than 500 chemical species of volatile organic compounds in urban air, including over 100 multi-substituted monoaromatic and volatile oxygenated hydrocarbons. We suggest that previous assessments of reactive carbon species may therefore have underestimated the contribution made by volatile organic compounds to urban pollution, particularly for compounds with more than six carbon atoms. Incorporating these species in predictive models should greatly improve our understanding of photochemical ozone yields and the formation of harmful secondary organic aerosols.
Supercritical-fluid extraction of synthetic pyrethroids from wool
Publisher: Elsevier BV
Date: 07-2000
DOI: 10.1016/S0165-022X(00)00054-3
Abstract: A stepwise approach was used to develop a supercritical fluid extraction (SFE) method for analysis of synthetic pyrethroids (SPs) on a wool matrix, commencing with a simple inert matrix to examine the solubility of the pyrethroids in the extraction fluid CO(2) and then extended to the real wool matrix. Chemometric approaches were used to determine the SFE optimum conditions. It was found that pyrethroids were readily extractable from an inert matrix over a wide range of pressure (170-350 atm) and at low temperature (<90 degrees C). Subambient hexane efficiently trapped the compounds from the depressurised fluid. Excessively high pressure and temperature resulted in poor trapping, isomerisation and possibly degradation of some components. With spiked wool s les method modifications focused on reducing the coextraction of grease, a bulk matrix component of raw wool. By using alumina (containing 8% moisture) and operating the extraction at 50 degrees C, 200 atm for 60 min, sufficiently clean extracts of pyrethroids suitable for gas chromatography-electron-capture detection analysis were obtained. The recoveries of all SPs were satisfactory (78-101%) over the range of 0.5-5 microg/g levels of these compounds. The precision of the entire analysis procedure was comparable to the conventional Soxhlet extraction method. Detection limits of some commonly used SPs for sheep treatment were also evaluated. Comparable results relative to those achieved by solvent extraction for incurred wool s les were obtained with a recovery of 81-85%. The results, however, suffered high uncertainties (R.S.D. approximately 19-24%) due to the small amount of wool s le taken in each extraction and the suspected inhomogeneity of the wool. Different persistences of cypermethrin isomers in wool were observed.
Development of a switchable multidimensional/comprehensive two-dimensional gas chromatographic analytical system
Publisher: Elsevier BV
Date: 02-2010
DOI: 10.1016/J.CHROMA.2009.12.078
Abstract: In this study, a new system for analysis using a dual comprehensive two-dimensional gas chromatography/targeted multidimensional gas chromatography (switchable GC x GC/targeted MDGC) analysis was developed. The configuration of this system not only permits the independent operation of GC, GC x GC and targeted MDGC analyses in separate analyses, but also allows the mode to be switched from GC x GC to targeted MDGC any number of times through a single analysis. By incorporating a Deans switch microfluidics transfer module prior to a cryotrapping device, the flow stream from the first dimension column can be directed to either one of two second dimension columns in a classical heart-cutting operation. Both second columns pass through the cryotrap to allow solute bands to be focused and then rapidly remobilized to the respective second columns. A short second column enables GC x GC operation, whilst a longer column is used for targeted MDGC. Validation of the system was performed using a standard mixture of compounds relevant to essential oil analysis, and then using compounds present at different abundances in lavender essential oil. Reproducibility of retention times and peak area responses demonstrated that there was negligible variation in the system over the course of multiple heart-cuts, and proved the reliable operation of the system. An application of the system to lavender oil, as a more complex s le, was carried out to affirm system feasibility, and demonstrate the ability of the system to target multiple components in the oil. The system was proposed to be useful for study of aroma-impact compounds where GC x GC can be incorporated with MDGC to permit precise identification of aroma-active compounds, where heart-cut multidimensional GC-olfactometry detection (MDGC-O) is a more appropriate technology for odour assessment.
Electrospray Mass Spectrometric Analysis and Photocatalytic Degradation of Polyethoxylate Surfactants Used in Wool Scouring
Publisher: American Chemical Society (ACS)
Date: 15-10-1994
DOI: 10.1021/AC00092A016
Quantification in comprehensive two-dimensional gas chromatography and a model of quantification based on selected summed modulated peaks
Publisher: Elsevier BV
Date: 03-2008
DOI: 10.1016/J.CHROMA.2007.10.041
Abstract: In common with all gas chromatography (GC) methods, comprehensive two-dimensional gas chromatography (GC x GC) has the potential to provide both qualitative and quantitative analysis. There are fundamental differences in the way one-dimensional (1D-GC) and GC x GC results are interpreted for these parameters. Since 1D-GC produces a single measured peak in the chromatogram, there is a single retention time, and associated with this a single peak response (either area or height). Peak area and height are related by peak width. GC x GC produces a series of modulated peaks at the detector. Thus, the peak metrics of retention, area and height for one component are now not simple single values for one peak, but rather are derived from the multiple peak distribution generated by the modulation process. The peak retention is interpreted in terms of two-dimensional coordinates in a retention plane. In this study, a brief background review to quantification in GC x GC is provided. Previous reviews cover aspects of quantitative GC x GC studies up to the year 2005, including different approaches to quantification, and reports of quantitative analysis with different detectors, for different compounds classes, and in different matrices. Other studies have developed chemometric approaches based on multivariate analysis to provide quantitative reporting of in idual compounds. The coverage of the earlier reviews has been updated to include material that has been presented since 2005 and includes considerations of valve-based modulation. Recently the modulation ratio (M(R)) concept was proposed and intended to clarify the meaning of modulation number (n(M)) in GC x GC, which was shown to be a rather poorly defined parameter. Based on the prior studies that introduced this concept, the role of quantitative analysis is investigated here through calculation of the peak areas and peak area ratios of selected series of modulated peaks in GC x GC. The application of isotopically labelled reference compounds for polycyclic aromatic hydrocarbon (PAH) analysis is used here to develop the quantitative metric approach. It is shown that by selecting the two or three major modulated peaks for solutes and internal standards, comparing the response ratio with the sum of all modulated peaks and also with the reference non-modulated result, quantification is statistically equivalent. Thus, adequate quantitative analysis and calibration can be accomplished by using selected major modulated peaks for each compound. This may simplify quantitative interpretation of GC x GC data.
Supercritical fluid extraction and gas Chromatographic electron capture detection method for sterol analysis of environmental water samples
Publisher: Royal Society of Chemistry (RSC)
Date: 1998
DOI: 10.1039/A804509G
Selective separation of Oxy-PAH from n-alkanes and pah in complex organic mixtures extracted from airborne PM2.5
Publisher: Springer Science and Business Media LLC
Date: 07-09-2010
Development of molecular markers associated with strawberry quality traits using a subtracted diversity array
Publisher: International Society for Horticultural Science (ISHS)
Date: 08-2014
Qualitative and quantitative study of nitrogen-containing compounds in heavy gas oil using comprehensive two-dimensional gas chromatography with nitrogen phosphorus detection
Publisher: Wiley
Date: 12-2007
Abstract: In this work, a GCxGC-nitrogen-phosphorus detection (NPD) methodology was developed to separate and quantitate nitrogen-containing compounds in Brazilian heavy gas oil. First, the NPD performance was improved in order to achieve best GCxGC performance. The geometry of this detector was also evaluated. The use of an extended jet improved significantly the peak shape. The GCxGC separation was studied using both first and second dimension columns with different internal diameters. The use of a thicker film in both dimensions provided better performance. LODs of 0.16-8.49 pg of in idual compounds were achieved. Two different extraction techniques of the neutral and basic nitrogen-containing compounds were also evaluated. The method using ion-exchange resins to separate neutral and basic nitrogen-containing compounds was more efficient than the method using modified silica. As an ex le, the amounts (microg/g) of each class reported were: indole (2.77), alkyl carbazoles ranging from C(0) to C(6+) (1.467), alkyl benzocarbazoles from C(0) to C(4+) (793), alkyl quinolines (31.2) and alkyl benzoquinolines (21.6) were quantitated.
Synthesis of benzodioxepinone analogues via a novel synthetic route with qualitative olfactory evaluation
Publisher: Wiley
Date: 05-2007
Evaluation of new stationary phases for the separation of fatty acid methyl esters
Publisher: Springer Science and Business Media LLC
Date: 08-03-2006
Interpretation of comprehensive two-dimensional gas chromatography data using advanced chemometrics
Publisher: Elsevier BV
Date: 2014
Optimization of the capillary electrophoresis separation of ranitidine and related compounds
Publisher: Elsevier BV
Date: 04-1997
Synthesis and qualitative olfactory evaluation of benzodioxepine analogues
Publisher: Wiley
Date: 05-2007
Fatty acid-binding protein 5 at the blood–brain barrier regulates endogenous brain docosahexaenoic acid levels and cognitive function
Publisher: Society for Neuroscience
Date: 16-11-2016
DOI: 10.1523/JNEUROSCI.1583-16.2016
Abstract: Fatty acid-binding protein 5 (FABP5) at the blood–brain barrier contributes to the brain uptake of docosahexaenoic acid (DHA), a blood-derived polyunsaturated fatty acid essential for maintenance of cognitive function. Given the importance of DHA in cognition, the aim of this study was to investigate whether deletion of FABP5 results in cognitive dysfunction and whether this is associated with reduced brain endothelial cell uptake of exogenous DHA and subsequent attenuation in the brain levels of endogenous DHA. Cognitive function was assessed in male and female FABP5 +/+ and FABP5 −/− mice using a battery of memory paradigms. FABP5 −/− mice exhibited impaired working memory and short-term memory, and these cognitive deficits were associated with a 14.7 ± 5.7% reduction in endogenous brain DHA levels. The role of FABP5 in the blood–brain barrier transport of DHA was assessed by measuring 14 C-DHA uptake into brain endothelial cells and capillaries isolated from FABP5 +/+ and FABP5 −/− mice. In line with a crucial role of FABP5 in the brain uptake of DHA, 14 C-DHA uptake into brain endothelial cells and brain capillaries of FABP5 −/− mice was reduced by 48.4 ± 14.5% and 14.0 ± 4.2%, respectively, relative to those of FABP5 +/+ mice. These results strongly support the hypothesis that FABP5 is essential for maintaining brain endothelial cell uptake of DHA, and that cognitive deficits observed in FABP5 −/− mice are associated with reduced CNS access of DHA. SIGNIFICANCE STATEMENT Genetic deletion of fatty acid-binding protein 5 (FABP5) in mice reduces uptake of exogenous docosahexaenoic acid (DHA) into brain endothelial cells and brain capillaries and reduces brain parenchymal levels of endogenous DHA. Therefore, FABP5 in the brain endothelial cell is a crucial contributor to the brain levels of DHA. Critically, lowered brain DHA levels in FABP5 −/− mice occurred in tandem with cognitive deficits in a battery of memory paradigms. This study provides evidence of a critical role for FABP5 in the maintenance of cognitive function via regulating the brain uptake of DHA, and suggests that upregulation of FABP5 in neurodegenerative diseases, where brain DHA levels are possibly diminished (e.g., Alzheimer's disease), may provide a novel therapeutic approach for restoring cognitive function.
Gas chromatography ‒ mass spectrometry for characterisation, assessment of quality and authentication of seed and vegetable oils
Publisher: Elsevier BV
Date: 05-2021
Early Prediction of Shiraz Wine Quality Based on Small Volatile Compounds in Grapes
Publisher: Hindawi Limited
Date: 23-05-2023
DOI: 10.1155/2023/2990963
Abstract: Wine producers perform early wine quality prediction based on berry morphology, the taste of the berry and the measurement of basic chemical parameters. Incorporating analysis on grape and wine volatiles could potentially achieve a more accurate prediction of wine quality, but forming these models requires careful selection of grapes, controlled fermentations, and standardised quality assessment. Here, we present 3 models for the prediction of quality in Shiraz wine. Modelling was performed by general regression analysis with 4-fold cross-validation: Model 1 (R2 = 99.97% and 4-foldR2 = 97.61%) for prediction of wine quality from wine volatiles, Model 2 (R2 = 99.89% and 4-foldR2 = 98.42%) for early prediction of wine quality from free-bound and glycosidically bound grape volatiles, and Model 3 (R2 = 91.62% and 4-foldR2 = 80.21%) for the prediction of wine quality from free grape volatiles only. The accuracy of these models presents an advancement in the early prediction of wine quality and provides a valuable tool to assist grape growers and winemakers to support the understanding of quality in the vineyard to better direct scarce resources.
Multidimensional gas chromatography beyond simple volatiles separation
Publisher: Royal Society of Chemistry (RSC)
Date: 16-05-2014
DOI: 10.1039/C4CC02018A
Abstract: Multidimensional separation in gas chromatography (MDGC) plays an important role in chemical analysis. This review presents selected literature on MDGC development and ex les of the range of functionality reported for MDGC methods over the past 2 decades. With the most obvious advantage of providing much greater capacity for resolving constituents of a s le, MDGC extends analytical efficiency to a more substantial molecular coverage, combined with operational flexibility. But by judicious choice of implementation method, important chemical information relating to the s le, its components, potentially physico-chemical properties, and improved capacity for absolute identification may be realised. S le-to-s le comparison is improved, and s le characterisation is facilitated especially when MDGC is combined with the informing power of modern mass spectrometry. Innovative MDGC arrangements allow high resolution coupled with spectroscopy and alternative bioassays, and delivers molecular elucidation in ways that are beyond just simple analysis of volatiles.
Comprehensive Two-Dimensional Gas Chromatography as a Bioanalytical Platform for Drug Discovery and Analysis
Publisher: MDPI AG
Date: 31-03-2023
DOI: 10.3390/PHARMACEUTICS15041121
Abstract: Over the last decades, comprehensive two-dimensional gas chromatography (GC×GC) has emerged as a significant separation tool for high-resolution analysis of disease-associated metabolites and pharmaceutically relevant molecules. This review highlights recent advances of GC×GC with different detection modalities for drug discovery and analysis, which ideally improve the screening and identification of disease biomarkers, as well as monitoring of therapeutic responses to treatment in complex biological matrixes. Selected recent GC×GC applications that focus on such biomarkers and metabolite profiling of the effects of drug administration are covered. In particular, the technical overview of recent GC×GC implementation with hyphenation to the key mass spectrometry (MS) technologies that provide the benefit of enhanced separation dimension analysis with MS domain differentiation is discussed. We conclude by highlighting the challenges in GC×GC for drug discovery and development with perspectives on future trends.
Capillary gas chromatography and gas chromatography-mass spectrometry of silicon(IV) derivatives of porphyrins with polar substituents
Publisher: Elsevier BV
Date: 11-1982
Comprehensive two-dimensional gas chromatography applied to illicit drug analysis
Publisher: Springer Science and Business Media LLC
Date: 17-07-2011
DOI: 10.1007/S00216-011-5234-6
Abstract: Multidimensional gas chromatography (MDGC), and especially its latest incarnation--comprehensive two-dimensional gas chromatography (GC × GC)--have proved advantageous over and above classic one-dimensional gas chromatography (1D GC) in many areas of analysis by offering improved peak capacity, often enhanced sensitivity and, especially in the case of GC × GC, the unique feature of 'structured' chromatograms. This article reviews recent advances in MDGC and GC × GC in drug analysis with special focus on ecstasy, heroin and cocaine profiling. Although 1D GC is still the method of choice for drug profiling in most laboratories because of its simplicity and instrument availability, GC × GC is a tempting proposition for this purpose because of its ability to generate a higher net information content. Effluent refocusing due to the modulation (compression) process, combined with the separation on two 'orthogonal' columns, results in more components being well resolved and therefore being analytically and statistically useful to the profile. The spread of the components in the two-dimensional plots is strongly dependent on the extent of retention 'orthogonality' (i.e. the extent to which the two phases possess different or independent retention mechanisms towards s le constituents) between the two columns. The benefits of 'information-driven' drug profiling, where more points of reference are usually required for s le differentiation, are discussed. In addition, several limitations in application of MDGC in drug profiling, including data acquisition rate, column temperature limit, column phase orthogonality and chiral separation, are considered and discussed. Although the review focuses on the articles published in the last decade, a brief chronological preview of the profiling methods used throughout the last three decades is given.
Chemotyping of new hop (Humulus lupulus L.) genotypes using comprehensive two-dimensional gas chromatography with quadrupole accurate mass time-of-flight mass spectrometry
Publisher: Elsevier BV
Date: 02-2017
DOI: 10.1016/J.CHROMA.2017.08.020
Abstract: Comprehensive two-dimensional gas chromatography with quadrupole accurate mass time-of-flight mass spectrometry (GC×GC-Q-TOFMS) is employed to profile Humulus lupulus L. (hop) essential oils. Comparison of characterised essential oils allows discrimination among chemotypes. Experimental and commercial hop genotypes displayed distinguishable chemotypic patterns among the volatile secondary metabolites making up their essential oils. In total, 210-306 unique compounds were detected (depending on specific genotype), with 99 of these compounds either positively or tentatively identified. Identified volatile secondary metabolites were grouped into esters, monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpene hydrocarbons, oxygenated sesquiterpenes and ketones. Terpenoids were the dominant chemical families across all hop genotypes analysed, representing between 67% and 90% of the total ion count. The multidimensional chromatographic profiles of hop essential oils are extremely information-rich, making GC×GC-Q-TOFMS useful for fast screening of new hybrid hop genotypes, and therefore informing breeding strategies to derive new commercial hop cultivars for the development of distinctive and desirable beers.
A new mechanistic pathway under Sonogashira reaction protocol involving multiple acetylene insertions
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C001109F
Abstract: An unreported product outcome from an intended Sonogashira coupling is presented. The generality of this finding has been demonstrated by screening of a range of pre-catalysts. Mechanistic studies are consistent with the tetra-aryl benzene product forming by interception of the aryl halide oxidative addition intermediate by repeated acetylene insertion.
Untargeted metabolic profiling of Eucalyptus spp. leaf oils using comprehensive two-dimensional gas chromatography with high resolution mass spectrometry: Expanding the metabolic coverage
Publisher: Springer Science and Business Media LLC
Date: 03-03-2017
Genotypic and environmental effects on flavor attributes of 'Albion' and 'Juliette' strawberry fruits
Publisher: Elsevier BV
Date: 12-2013
Relationships in Gas Chromatography—Fourier Transform Infrared Spectroscopy—Comprehensive and Multilinear Analysis
Publisher: MDPI AG
Date: 13-05-2020
DOI: 10.3390/SEPARATIONS7020027
Abstract: Molecular spectroscopic detection techniques, such as Fourier transform infrared spectroscopy (FTIR), provides additional specificity for isomers where often mass spectrometry (MS) fails, due to similar fragmentation patterns. A hyphenated system of gas chromatography (GC) with FTIR via a light-pipe interface is reported in this study to explore a number of GC–FTIR analytical capabilities. Various compound classes were analyzed—aromatics, essential oils and oximes. Variation in chromatographic peak parameters due to the light-pipe was observed via sequentially-located flame ionization detection data. Unique FTIR spectra were observed for separated mixtures of essential oil isomers having similar mass spectra. Presentation of GC×FTIR allows a ‘comprehensive’-style experiment to be developed. This was used to obtain spectroscopic/separation profiles for interconverting oxime species with their in idual spectra in the overlap region being displayed on a color contour plot. Partial least square regression provides multivariate quantitative analysis of co-eluting cresol isomers derived from GC–FTIR data. The model resulted in an R2 of 0.99. Prediction was obtained with R2 prediction value of 0.88 and RMSEP of 0.57, confirming the method’s suitability. This study explores the potential of GC–FTIR hyphenation and re-iterates its value to derive unambiguous and detailed molecular information which is complementary to MS.
A report on the comprehensively coupled chromatography conference (4C) - Riva del Garda - With a view to China, June 2007
Publisher: Wiley
Date: 08-2006
Determination of volatile compounds in Brazilian distilled cachaça by using comprehensive two-dimensional gas chromatography and effects of production pathways
Publisher: Elsevier BV
Date: 04-2009
DOI: 10.1016/J.CHROMA.2008.10.061
Abstract: Comprehensive two-dimensional gas chromatography (GCxGC) was applied to the study of cachaça production. Effects of bidistillation, and the use of charcoal filtration in the production of artisan cachaça, as well as the effects of multi-distillation on volatile products in commercial cachaça were investigated. Volatile compounds were collected and concentrated onto a polyacrylate solid-phase microextraction fibre, and analyzed using GCxGC on a non-polar (BPX5)-polar (BP20) column set. More than 100 compounds, comprising various homologous series were tentatively identified using MS library matching and comparison with retention indices. Phthalate organic contamination following the use of ion exchange resin for removal of copper ion was evident. Charcoal successfully removes this contamination product. Prediction of compounds within particular homologous series aids component identification.
Dual NPD/ECD detection in comprehensive two-dimensional gas chromatography for multiclass pesticide analysis
Publisher: Wiley
Date: 10-2008
Abstract: A comprehensive 2-D GC (GC x GC) dual detection system, coupled to nitrogen-phosphorus detection (NPD) and electron capture detection (ECD) has been developed for multiclass pesticide analysis in vegetable s le matrices. The second dimension column was connected to the parallel detectors via a microfluidic splitting device. The s le set comprised 17 organochlorine pesticides, 15 organophosphorus insecticides and 9 N-containing fungicides. Selective detection of vegetable s le extracts provides increased information content through simultaneous, correlated GC x GC plots for both ECD and NPD, which demonstrated improved separation of pesticide standards from each other, and from the s le matrix. The efficiency of NPD and ECD modes was investigated and compared the ECD produced broader peaks, with the ECD generating greater response as measured by S/N ratio. Accuracy and precision of the approach were determined as repeatability and reproducibility for selected pesticides. The RSDs of the intraday (n = 5) and interday (3 days) analyses of the selected pesticides are less than 2.5 and 10%, respectively. The relative ratio of the ECD/NPD response is proposed to offer additional identification of in idual pesticides, in addition to the (1)t(R) and (2)t(R) retention coordinates ratios vary from 19 to over 1000 for selected pesticides that also exhibit ECD and NPD activities.
Application of headspace solid-phase microextraction (HS-SPME) and comprehensive two-dimensional gas chromatography (GC x GC) for the chemical profiling of volatile oils in complex herbal mixtures
Publisher: Wiley
Date: 04-2004
Abstract: The coupling of headspace solid‐phase microextraction (HS‐SPME) with comprehensive two‐dimensional gas chromatography (GC×GC) was shown to be a powerful technique for the rapid s ling and analysis of volatile oils in complex herbal materials. When compared to one‐dimensional (1‐D) GC, the improved analytical capabilities of GC×GC in terms of increased detection sensitivity and separation power were demonstrated by using HS‐SPME/GC×GC for the chemical profiling (fingerprinting) of essential/volatile oils contained in herbal materials of increasing analytical complexity. More than 20 marker compounds belonging to Panax quinquefolius (American ginseng) can be observed within the 2‐D contour plots of ginseng itself, a mixture of ginseng and another important herb ( P. quinquefolius/Radix angelicae sinensis ), as well as a mixture of ginseng and three other herbs ( P. quinquefolius /R. angelicae sinensis/R. astragali/R. rehmanniae preparata ). Such analytical capabilities should be important towards the authentication and quality control of herbal products, which are receiving increasing attention as alternative medicines worldwide. In particular, the presence of Panax in the herb formulation could be readily identified through its specific peak pattern in the 2‐D GC×GC plot.
Preparative gas chromatography as a sample preparation approach
Publisher: Elsevier
Date: 2012
Microfluidic valve geometries and possibilities for flow switching in gas chromatography
Publisher: SPIE
Date: 26-12-2009
DOI: 10.1117/12.814896
Evaluation of reversible interconversion in comprehensive two-dimensional gas chromatography using enantioselective columns in first and second dimensions
Publisher: Elsevier BV
Date: 07-2015
DOI: 10.1016/J.CHROMA.2015.05.049
Abstract: The reversible molecular interconversion behaviour of a synthesised oxime (2-phenylpropanaldehyde oxime (C6H5)CH(CH3)CHN(OH)) was investigated by both, single dimensional gas chromatography (1D GC) and comprehensive two-dimensional gas chromatography (GC×GC). Previous studies on small molecular weight oximes were extended to this larger aromatic oxime (molar mass 149.19gmol(-1)) with interest in the extent of interconversion, enantioselective resolution, and retention time. On a polyethylene glycol (PEG wax-type) column, a characteristic interconversion zone between two antipodes of E and Z isomers was formed by molecules which have undergone isomerisation on the column (E⇌Z). The extent of interconversion was investigated by varying chromatographic conditions (oven temperature and carrier flow rate) to understand the nature of the behaviour observed. The extent of interconversion was negligible in both enantioselective and methyl-phenylpolysiloxane phase-columns, correlating with the low polarity of the stationary phase. In order to obtain isomerisation along with enantio-resolution, a wax-type and an enantioselective column were coupled in either enantioselective-wax or wax-enantioselective order. The most appropriate column arrangement was selected for study by using a GC×GC experiment with either a wax-phase or phenyl-methylpolysiloxane phase as (2)D column. In addition to evaluation of these fast elution columns, a long narrow-bore enantioselective column (10m) was introduced as (2)D, providing an enantioselective-PEG (coupled-column ensemble: (1)D1+(1)D2)×enantioselective ((2)D) column combination. In this instance, the (1)D1 enantioselective column provides enantiomeric separation of the corresponding enantiomers ((R) and (S)) of (E)- and (Z)-2-phenylpropanaldehyde oxime, followed by E/Z isomerisation in the coupled (1)D2 PEG (reactor) column. The resulting chromatographic interconversion region was modulated and separated into either E/Z isomers (achiral (2)D column) or into the respective (R) and (S) enantiomers of the E/Z isomers when using a (2)D enantioselective column. With this arrangement, the isomers underneath the broad interconversion plateau in 1D elution profiles, including the enantiomers, could be resolved, illuminating salient features and understanding of the molecular reversible process of the interconverting molecules during the chromatographic elution. The two-dimensional patterns (contour plots), resulting from the combination of interconversion process and chiral separation, are discussed phenomenologically.
Shape selectivity: A key factor in comprehensive two-dimensional gas chromatographic analysis of toxic PCBs
Publisher: Wiley
Date: 2001
DOI: 10.1002/MCS.10011
Fast comprehensive two-dimensional gas chromatography method for fatty acid methyl ester separation and quantification using dual ionic liquid columns
Publisher: Elsevier BV
Date: 10-2013
DOI: 10.1016/J.CHROMA.2013.08.099
Abstract: Safflower oil is a complex mixture of C18 saturated and unsaturated fatty acids amongst other fatty acids, and achieving separation between these similar structure components using one dimensional gas chromatography (GC) may be difficult. This investigation aims to obtain improved separation of fatty acid methyl esters in safflower oil, and their quantification using comprehensive two-dimensional GC (GC×GC). Here, GC×GC separation is accomplished by the coupling of two ionic liquid (IL) column phases: the combination of SLB-IL111 with IL59 column phases was finally selected since it provided excellent separation of a FAME standard mixture, as well as fatty acids in safflower and linseed oil, compared to other tested column sets. Safflower oil FAME were well separated in a short run of 16min. FAME validation was demonstrated by method reproducibility, linearity over a range up to 500mgL(-1), and limits of detection which ranged from 1.9mgL(-1) to 5.2mgL(-1) at a split ratio of 20:1. Quantification was carried out using two dilution levels of 200-fold for major components and 20-fold for trace components. The fatty acids C15:0 and C17:0 were not reported previously in safflower oil. The SLB-IL111/IL59 column set proved to be an effective and novel configuration for separation and quantification of vegetable and animal oil fatty acids.
Fast comprehensive two-dimensional gas chromatography with cryogenic modulation
Publisher: American Chemical Society (ACS)
Date: 15-05-2007
DOI: 10.1021/AC062351N
Abstract: The fast separation of a mixture of 29 compounds by using comprehensive two-dimensional gas chromatography is reported. Capillary column sets with shorter lengths and smaller inner diameter in both the first and second dimensions have been tested, for both fast chiral and achiral separations. Fast chiral separations, which included enantiomer separations of limonene, linalool, citronellol, and alpha-isomethylionone, were achieved within 23 min, which corresponds to approximately 2-fold faster than analyses under conditions previously considered as normal. Fast achiral separations, which do not have the restriction of requiring a minimum quality of chiral resolution, were obtained within 5 min, which is markedly faster than separations on the normal column set under conditions more commonly employed. The achiral fast GC x GC method used a 5 m x 0.1 mm i.d. first dimension column, interfaced to a 0.3 m x 0.05 mm i.d. second column, with temperature program rate of 35 degrees C.min-1 a modulation period of 1 s was employed. Peak widths at baseline on the first column were a little over 1 s, while modulated peak widths at half-height recorded with a flame ionization detector operating at 200 Hz were approximately 30 ms. The benefits and limitations of GC x GC for fast chiral and achiral separations are reported and discussed.
Variation of wine preference amongst consumers is influenced by the composition of salivary proteins
Publisher: Cold Spring Harbor Laboratory
Date: 27-03-2023
DOI: 10.1101/2023.03.27.534455
Abstract: The preferences of consumers for different flavours and aromas in wine are varied and may be explained by inherent factors such as cultural background, wine education and personal taste of the wine consumer. Wine flavour as perceived in the mouth includes aroma compounds released through the retronasal pathway which are shaped by interactions with saliva. Saliva and wine interactions could provide an explanation as to why wine tasters express different preferences for wine. To test this hypothesis, 13 Western and 13 Chinese experienced wine tasters were recruited. Sensory evaluation was performed in formal surroundings to acquire free description-based and perceived sensory intensity data using the Pivot ® Profile and continuous scale assessment, respectively. Participants’ saliva s les were collected before the sensory evaluation and spiked into a wine s le to investigate the impact on the wine volatile release using GC×GC−MS. Saliva s les were subjected to enzyme activity assays and protein composition profiling by Tandem Mass Tag (TMT) quantitative proteomics. The wine tasters showed differences in wine flavour perception, which was supported by the difference in wine volatile release resulting from the addition of saliva. The two groups of participants did not have significant differences in total salivary protein concentrations or the amounts of esterase and α-amylase. However, statistically significant variations in the concentrations of specific proteins (proline-rich proteins (PRPs) and lipocalin-1 (LCN-1) p 0.01) were found between the two groups. Significant correlations between perceived intensities of wine attributes and concentrations of PRPs and LCN-1 were observed. These results indicate that the composition of proteins in saliva are a factor that influences wine perception and preference. Our results provide a biochemical basis to understanding preference for food based on interactions between aroma compounds and salivary proteins and could be used to suggest foods or beverages to particular cultural groups.
Fast GC × GC with short primary columns
Publisher: American Chemical Society (ACS)
Date: 04-02-2006
DOI: 10.1021/AC0519413
Abstract: A novel approach to comprehensive two-dimensional gas chromatography (GCxGC) separations is presented, which operates in a new region of the "GCxGC optimization pyramid". The technique relies on the use of short primary columns to decrease elution temperatures (Te) of analytes from the primary column, with a Te reduction of up to 50 degrees C illustrated. This in turn has implications that will expand the areas where GCxGC can be used, as decreased elution temperatures will allow GCxGC to be applied to mixtures of less volatile compounds or permit the use of less thermally stable stationary phases in the column ensemble. As well, it will allow GCxGC to be applied to thermally labile compounds through a reduction in elution temperature. With short primary columns, resolution and efficiency in the first dimension is sacrificed, but speed is gained however, the second column in GCxGC provides additional resolution and separation of compounds of differing chemical properties. Thus, it is possible to recover some of the analytical separation power of the system to provide resolution of target analytes from s le impurities. As an ex le, a case study using short primary columns for the separation of natural pyrethrins, which degrade above 200 degrees C, is described. Even with the sacrifices of overall separation power that are made, there is still sufficient resolution available to separate the six natural pyrethrins from each other and the complex chrysanthemum extract matrix. The use of cold-on-column injection, a short primary column, and a high carrier gas flow rate allow the pyrethrins to be eluted below 200 degrees C, with separation in 17 min and complete resolution from s le matrix.
Liquid chromatography fractionation with gas chromatography/mass spectrometry and preparative gas chromatography-nuclear magnetic resonance analysis of selected nonylphenol polyethoxylates
Publisher: Elsevier BV
Date: 07-2011
DOI: 10.1016/J.CHROMA.2011.04.079
Abstract: Commercial nonylphenol polyethoxylates, designated as NPnEOs, where n is the number of ethoxy groups, comprise a range of ethoxylate groups. According to the starting material nonylphenol, they may also be composed of a complex mix of isomeric nonyl substituents. In order to study more fully the heterogeneity arising from both the ethoxylate and nonyl groups, a mixture of NPnEOs is first fractionated by normal phase liquid chromatography (NPLC) into separate fractions comprising in idual ethoxymers, n. Preparative collection of each early elution ethoxymer fraction allows further separation of different isomeric nonyl group components by using analytical gas chromatography/mass spectrometry (GC/MS). The nonyl isomers are not resolved in the NPLC method. The distribution of the isomeric nonyl side chain of different ethoxymers bears close resemblance with each other, and also with the original nonylphenol starting material, although separation efficiency of the nonyl isomers for each ethoxymer decreases with increasing ethoxymer number. Mass spectrometry of the separated isomers display close similarity for presumed equivalent isomers in each fraction, based on elution order of the nonyl isomers. This suggests that each corresponding peak has the same isomer structure. Mass spectra are interpreted based on branching within the nonyl side chain. Preparative GC coupled with MS and nuclear magnetic resonance spectroscopy elucidated the molecular structure of one of the resolved isomers as 4-(1,3-dimethyl-1-propyl-butyl)-phenol diethoxylate.
Identification of odour-active compounds of pasteurised orange juice using multidimensional gas chromatography techniques
Publisher: Elsevier BV
Date: 09-2015
DOI: 10.1016/J.FOODRES.2015.06.014
Abstract: Odour-active compounds present in pasteurised orange juice were identified by gas chromatography-olfactometry (GC-O) employing heart-cut multidimensional GC techniques with olfactometry (O) and mass spectrometry (H/C MDGC-O/MS) and comprehensive two-dimensional gas chromatography-accurate mass time-of-flight MS (GC×GC-accTOFMS). Headspace solid phase microextraction s ling proved to be qualitatively adequate for the analysis of pasteurised orange juice. The GC-O approach distinguished 13 potent odour regions (detection frequency≥3) in the orange juice extract, in which 7 regions were then subjected to detailed identification of the compounds that contribute to the odour, by using higher resolution H/C MDGC-O/MS. This analysis permitted the odour-active peaks to be better resolved on the
Comprehensive two-dimensional gas chromatography with flame ionization and time-of-flight mass spectrometry detection: Qualitative and quantitative analysis of west Australian sandalwood oil
Publisher: Oxford University Press (OUP)
Date: 09-2004
DOI: 10.1093/CHROMSCI/42.8.417
Abstract: The use of gas chromatography (GC)-mass spectrometry (MS), GC-time-of-flight MS (TOFMS), comprehensive two-dimensional GC (GCxGC)-flame ionization detection (FID), and GCxGC-TOFMS is discussed for the characterization of the eight important representative components, including Z-alpha-santalol, epi-alpha-bisabolol, Z-alpha-trans-bergamotol, epi-beta-santalol, Z-beta-santalol, E,E-farnesol, Z-nuciferol, and Z-lanceol, in the oil of west Australian sandalwood (Santalum spicatum). Single-column GC-MS lacks the resolving power to separate all of the listed components as pure peaks and allow precise analytical measurement of in idual component abundances. With enhanced peak resolution capabilities in GCxGC, these components are sufficiently well resolved to be quantitated using flame ionization detection, following initial characterization of components by using GCxGC-TOFMS.
Comprehensive two-dimensional gas chromatography/mass spectrometric analysis of pepper volatiles
Publisher: Wiley
Date: 29-08-2006
DOI: 10.1002/RCM.2665
Abstract: The headspace compositions of 13 pepper and peppercorn s les of different species, colloquially also referred to as pepper, were analyzed, and more than 300 compounds were tentatively characterized by means of comprehensive two-dimensional gas chromatography in tandem with flame ionization detection, quadrupole mass spectrometric detection and time-of-flight mass spectrometric detection (GC x GC-FID, GC x GC/qMS and GC x GC/TOFMS, respectively). The analysis of volatile organic compounds (VOCs) was performed after solid-phase microextraction (SPME) using a 75-microm PDMS/DVB fibre. Fingerprint comparison between the three techniques permitted peaks to be assigned in the GC x GC-FID experiment based on the analogous MS analysis, taking into account retention shifts arising from method variations. When using GC x GC/TOFMS, about five times more peaks were identified than in GC x GC/qMS. Retention indices for all peaks were calculated in the bi-dimensional column set comprising of a 5% phenyl polysilphenylene-siloxane primary column and a polyethylene glycol second column. The spectra obtained by both mass detection techniques (qMS and TOFMS) give very similar results when spectral library searching was performed. The majority of the identified compounds eluted as pure components as a result of high-resolution GC x GC separations, which significantly reduces co-elution, and therefore increases the likelihood that pure spectra can be obtained. The differences between TOFMS and qMS (in fast scanning mode) spectra were generally small. Whilst spectral quality and relative ion ratios across a narrow peak (e.g. w(b) approximately 100-150 ms) do vary more for the fast peaks obtained in GC x GC/qMS operation, than with TOFMS, in general adequate spectral matching with the library can be achieved.
Erratum: Temperature profiles and heat dissipation in capillary electrophoresis (Analytical Chemistry (2006) 78, (2684-2693))
Publisher: American Chemical Society (ACS)
Date: 07-03-2007
DOI: 10.1021/AC070216K
System design for integrated comprehensive and multidimensional gas chromatography with mass spectrometry and olfactometry
Publisher: American Chemical Society (ACS)
Date: 26-10-2012
DOI: 10.1021/AC301847Y
Abstract: An integrated system having the combined capability to perform gas chromatography (GC), comprehensive two-dimensional GC (GC × GC), and target heart-cut multidimensional GC (MDGC) using olfactometry (O), flame ionization (FID), and/or mass spectrometry (MS) detection is described. This combines a number of contemporary GC methods into a single instrument to provide very high resolution profiling of a s le. This provides initial assessment of volatile compound composition through GC × GC analysis with FID, which can be correlated with GC analysis using parallel O and FID detection. Subsequent microfluidic (Deans) switching selects regions (heart-cuts) of the chromatographic elution from the first dimension ((1)D) column for further resolution on a long second dimension ((2)D(L)) column for parallel detection of O and MS. Various (2)D(L) operational conditions, as well as the effect of different heart-cut (H/C) duration, were compared. The favored mode involves cryotrapping of heart-cuts, cooling the oven, and reducing carrier flow to offer greater efficiency. An analytical strategy that incorporates GC-FID/O, GC × GC-FID, and MDGC-MS/O analyses with cumulative solid phase microextraction (SPME) s ling for volatile s le enrichment is presented in this work. Excellent qualitative and quantitative performance was demonstrated with a Shiraz wine s le and an allergens mixture, with tentative identification of acetic acid, octen-3-ol, and ethyl octanoate as aroma contributors in Shiraz wine and determination of β-damascenone (floral odor) well separated from hexanoic acid (sweaty odor). A novel approach to obtain (2)D retention indices is reported, allowing matching of mass spectral, (1)I (retention index in (1)D) and (2)I (retention index in (2)D) data. The method employs the same olfactory detector at the end of the (1)D and (2)D(L) columns.
In Silico Modeling of Hundred Thousand Experiments for Effective Selection of Ionic Liquid Phase Combinations in Comprehensive Two-Dimensional Gas Chromatography
Publisher: American Chemical Society (ACS)
Date: 02-02-2016
DOI: 10.1021/ACS.ANALCHEM.5B03688
Abstract: The selection of the best column sets is one of the most tedious processes in comprehensive two-dimensional gas chromatography (GC × GC) where a multitude of choices of column sets could be employed for an in idual s le analysis. We demonstrate analyte/stationary phase dependent selection approaches based on the linear solvation energy relationship (LSER), which is a reliable concept for the study of interaction mechanisms and retention prediction with a large database pool of columns and compounds. Good correlations between our predicted results, with experimental results reported in the literature, were obtained. The developed approaches were applied to the simulation of 157 920 in idual experiments in GC × GC, focusing on the application of 30 nonionic liquid and 111 ionic liquid (IL) stationary phases for separation of some ex le sets of model compounds present in practical s les. The best column sets for each s le separation could then be extracted according to maximizing orthogonality, which estimates the quality of separation.
Electrokinetic removal of creosote from treated timber waste: A comprehensive gas chromatographic view
Publisher: Springer Science and Business Media LLC
Date: 09-02-2010
Time-resolved cryogenic modulation for targeted multidimensional capillary gas chromatography analysis
Publisher: Elsevier BV
Date: 09-2000
DOI: 10.1016/S0021-9673(00)00122-9
Abstract: Multidimensional gas chromatography (MDGC) is performed in a new manner, described in this paper. The method incorporates two directly coupled columns and employs a longitudinally modulated cryogenic trap located between the columns. No heartcutting process is used, but rather a method better termed selected zone compression pulsing is used. Compared with normal MDGC, where primary column effluent has to be temporarily erted either to a monitor detector or to the second dimension column, the new procedure in its simplest mode passes all of the first column effluent to the second column. It is simply the times at which the modulation of the trap is performed that determines which target solutes will be selected for enhanced separation. This approach allows almost instantaneous separation of selected zones on the second column, and has the potential to significantly simplify the MDGC method. Since data are presented in a time-response format, and do not require transformation as previously described for comprehensive GC when using the longitudinal modulator, quantitation and report generation are essentially the same as in any GC method and data system. Advantages also include significant sensitivity improvement. By using cryofocussing, and benefiting from the zone compression effects along with fast GC conditions on the second dimension, new possibilities for MDGC can be realised. The method is demonstrated by using a mixture of semi-volatile aromatic hydrocarbons.
Application of comprehensive two-dimensional gas chromatography with nitrogen-selective detection for the analysis of fungicide residues in vegetable samples
Publisher: Elsevier BV
Date: 10-2006
DOI: 10.1016/J.CHROMA.2006.07.035
Abstract: Comprehensive two-dimensional gas chromatography (GCxGC) with nitrogen-phosphorus detection (NPD) has been investigated for the separation and quantitation of fungicides in vegetable s les. The detector gas flows (H(2), N(2) and air) were adjusted to achieve maximum response of signal whilst minimizing peak width. The comparison of different column sets and selection of the temperature program were carried out with a mixture of nine N-containing standard fungicides, eight of which were chlorinated. The results from GCxGC-NPD and GCxGC with micro electron-capture detection (muECD) were compared. External calibrations of fungicides were performed over a concentration range from 1 to 1,000 microgL(-1). The peak area calibration curves generally had regression coefficients of R(2)>0.9980, however for iprodione which was observed to undergo on-column degradation, an R(2) of 0.990 was found. The limit of detection (LOD) and limit of quantitation (LOQ) were less than about 74 and 246 ng L(-1), respectively. The intra-day and inter-day RSD values were measured for solutions of concentration 0.100, 0.500 and 1.50 mg L(-1). For the 0.500 mg L(-1) solution, intra- and inter-day precision of peak area and peak height for most of the pesticides were about 2% and 8%, respectively. Excellent linearity was observed for these standards, from 0.001 to 25.00 mg L(-1). The standard mixture peak positions were identified by using GCxGC with quadrupole mass spectrometry (qMS). To illustrate the potential and the versatility of both GCxGC-NPD and GCxGC-muECD, the method was applied to determination of fungicides in a vegetable extract. Decomposition of one fungicide standard (iprodione) during chromatography elution was readily observed in the two-dimensional (2D) GCxGC plot as a diagonal ridge response in the 2D chromatogram between the degrading compound and the decomposition product.
Characterisation of capillary ionic liquid columns for gas chromatography-mass spectrometry analysis of fatty acid methyl esters
Publisher: Elsevier BV
Date: 11-2013
DOI: 10.1016/J.ACA.2013.07.002
Abstract: Due to their distinct chemical properties, the application of ionic liquid (IL) compounds as gas chromatography (GC) stationary phases offer unique GC separation especially in the analysis of geometric and positional fatty acid methyl ester (FAME) isomers. Elution behaviour of FAME on several commercialised IL capillary columns including phosphonium based SLB-IL59, SLB-IL60, SLB-IL61 and SLB-IL76 and imidazolium based SLB-IL82, SLB-IL100, and SLB-IL111 as well as a general purpose column SLB-5ms, were evaluated in gas chromatography-mass spectrometry (GC-MS) analysis. The phases were further characterised by using a linear solvation energy relationship (LSER) approach according to the equivalent chain length (ECL) index of FAME. Among all tested IL columns, elution temperatures of saturated FAME increased as their McReynolds' polarity value decreased, except for IL60. ECL values increased markedly as the stationary phase polarity increased, particularly for the polyunsaturated FAME. The LSER study indicated a lowest l/e value at 0.864 for IL111, displaying phase selectivity towards unsaturated FAME, with higher peak capacity within a carbon number isomer group. s and e descriptors calculated from LSER were validated by excellent correlation with dipole moments and lowest unoccupied molecular orbital (LUMO) energies, with R(2) values of 0.99 and 0.92 respectively, calculated using GAUSSIAN.
Rapid sequential heart-cut multidimensional gas chromatographic analysis
Publisher: Elsevier BV
Date: 11-2004
DOI: 10.1016/J.CHROMA.2004.05.048
Abstract: A method is described which allows the sequential fast analysis of heart-cuts taken during the first column elution of an essential oil s le in a multidimensional gas chromatography experiment. In this investigation, a relatively short, narrow bore capillary column is used in the second dimension, with fast cryogenic modulation permitting rapid delivery of cryofocussed heart-cuts into the second column of the multidimensional arrangement. In this implementation, the total analysis time on the second column is of the order of 30 s, which is less than the duration of the s led heart-cuts (1 min), with peak theoretical efficiencies of about 7000 m(-1). Thus, the method should allow on-line heart-cutting of as many discrete heart-cuts as one may require from the first dimension chromatogram, and so two-dimensional separation can be achieved for almost the whole s le in one single analysis without the need for repeat injections or cycling of the oven temperature. The method is demonstrated by the transfer and rapid re-injection of 1 min heart-cuts taken from an initial separation stage of peppermint essential oil. The cryofocussing and fast analysis step is shown to increase signal response by up to 40-fold. Total peak capacity in the described system is measured to be of the order of 1800, with capacities of about 20-30 for each 30 s second dimension analysis. By increasing the frequency of s ling to remove excessive (unused) time to develop the 2D separation, it should be possible to achieve peak capacities of 5000 or more baseline resolved peaks.
CE methods applied to the analysis of micronutrients in foods
Publisher: Wiley
Date: 10-2007
Abstract: This article reviews the applications of CE that are relevant to the analysis of small molecules in foods. CE has been applied to a wide range of important areas of food analysis and is rapidly being established as an alternative technique to chromatographic methods including HPLC and GC within analytical food and research laboratories. In recent years the analysis of food by CE has become more frequent and important and as such a variety of compounds have been separated and quantified. Although many other analytes have been detected by CE, this review will highlight areas relating primarily to the rather broad chemical classes of free amino acids, carbohydrates, organic acids, vitamins and a variety of antioxidants. In addition, information relating to the analyte, s le matrix, mode of CE employed, scope of the methodology and the detection and derivatization of the small molecules are considered and discussed.
Simulation of elution profiles for two-dimensional dynamic gas chromatographic experiments
Publisher: American Chemical Society (ACS)
Date: 24-07-2003
DOI: 10.1021/AC0301144
Abstract: The interconversion of E and Z isomers of acetaldoxime 1 and butyraldoxime 2 have been investigated by comprehensive two-dimensional dynamic gas chromatography (DGCxDGC) and computer simulation. Time-resolved cryogenic modulation is capable of revealing the precise isomeric ratio as a fine structure under the dynamic elution profile, which is characterized in one-dimensional experiments by a plateau formation or peak coalescence caused by interconversion of the isomers during the separation process. The chromatographic theoretical plate model has been extended for the computer simulation of comprehensive two-dimensional dynamic chromatographic experiments. A novel program, ChromWin 2D, based on the new algorithm has been developed for computer simulation to evaluate and predict the elution profiles of DGCxDGC experiments. ChromWin 2D allows the determination of rate constants and barriers of isomerization, epimerization, and enantiomerization processes occurring during chromatographic separations. The Eyring activation parameters of the E/Z and Z/E isomerization barriers in the presence of the stationary phase BP21 (poly(ethylene glycol) terephthalate terminated) were determined by temperature-dependent experiments between 80 and 90 degrees C for 1 and 70 and 130 degrees C for 2. The thermodynamic Gibbs free energy of the E/Z equilibrium of the isomers has been determined from the time-resolved chromatograms by cryogenic modulation. The method described here constitutes a new and important tool for the determination of isomerization barriers, which are of great interest, for ex le, for the quantitative determination of derivatized aldehydes, such as dinitrophenylhydrazine derivatives, in trace analysis.
Simultaneous analysis of seven alkaloids in Coptis-Evodia herb couple and Zuojin pill by UPLC with accelerated solvent extraction
Publisher: Wiley
Date: 16-08-2010
Abstract: A rapid, sensitive, and accurate ultra‐performance liquid chromatography‐UV detection method was developed and validated for simultaneous determination of seven active alkaloids, berberine, palmatine, coptisine, jatrorrhizine, epiberberine, evodiamine, and rutaecarpine, in the Coptis‐Evodia herb couple and the Zuojin pill preparation. The original validated method had a total time of about 11 min, which was reduced to 4.7 min by further optimization of gradient elution conditions with eluent A comprising water/methanol/formic acid (v/v/v, 90:10:0.1) and eluent B ACN. An accelerated solvent extraction method was used for the rapid extraction of herb products and pill preparations. Linear behavior over the investigated concentration ranges was observed, with values of r 2 greater than 0.9987 for all analytes. Experiment results were satisfactory for both intra‐day and inter‐day precision, and method accuracy. Method recovery ranged from 95.7 to 103.5% based on pure reference standards. The validated method was successfully applied to determine amounts of bioactive alkaloid compounds in five s les, in the Coptis‐Evodia herb couple, and the commercial Zuojin pill products. The developed method achieved baseline resolution for all seven main basic compounds and is suitable for use as a routine procedure for the rapid identification and quantification of basic compounds in the Coptis‐Evodia herb couple and related products.
Chemical signature of ecstasy volatiles by comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 06-2011
DOI: 10.1016/J.FORSCIINT.2010.11.008
Abstract: A method for ecstasy volatiles 'signature' analysis based on two-dimensional gas chromatography separation and time-of-flight mass spectrometry detection (GC×GC-TOFMS) is presented. Organic impurity volatiles were extracted by head space solid phase microextraction (HS-SPME). The final column phase choice of the four different column combinations tested was a low-polarity 5% phenyl polysilphenylene-siloxane coupled with a polyethylene glycol phase, which best displayed the complex impurity profile. Second dimension ((2)D) retention time reproducibility was found to be about 1% RSD, and area reproducibility of SPME s ling was just over 5% RSD for compounds with S/N ratio of about 100. High similarity of TOFMS spectra of impurities was obtained against commercial MS libraries. 16 components from the two-dimensional profiles were selected for comparison of the 24 ecstasy tablets, most of which proved to be benzodioxole derived compounds. All tablets were correctly classified in eight groups according to their post-tabletting characteristics, when appropriate data pre-treatment was applied. Principal component analysis revealed clustering of s les according to the country of origin. S les from Macedonia were elevated in N-formyl-MDMA and N-acetyl-MDMA while s les from Australia were elevated in 3,4-methylenedioxypropane and 3,4-methylenedioxyacetophenone. Furthermore, three components were found to be unique for one of the source countries. The additional separation of components on the (2)D column, increased response due to modulation, high acquisition rate with full mass spectra using TOFMS detection, and MS deconvolution extend the possibility of detecting additional markers and route-specific components, especially of low abundant, polar components.
Reliable electrophoretic mobilities free from Joule heating effects using CE
Publisher: Wiley
Date: 10-2007
Abstract: Ionic electrophoretic mobilities determined by means of CE experiments are sometimes different when compared to generally accepted values based on limiting ionic conductance measurements. While the effect of ionic strength on electrophoretic mobility has been long understood, the increase in the mobility that results from Joule heating (the resistive heating that occurs when a current passes through an electrolyte) has been largely overlooked. In this work, a simple method for obtaining reliable and reproducible values of electrophoretic mobility is described. The electrophoretic mobility is measured over a range of driving powers and the extrapolation to zero power dissipation is employed to eliminate the effect of Joule heating. These extrapolated values of electrophoretic mobility can then be used to calculate limiting ionic mobilities by making a correction for ionic strength this somewhat complicated calculation is conveniently performed by using the freeware program PeakMaster 5. These straightforward procedures improve the agreement between experimentally determined and literature values of limiting ionic mobility by at least one order of magnitude. Using Tris-chromate BGE with a value of conductivity 0.34 S/m and ionic strength 59 mM at a modest dissipated power per unit length of 2.0 W/m, values of mobility for inorganic anions were increased by an average of 12.6% relative to their values free from the effects of Joule heating. These increases were accompanied by a reduction in mobilities due to the ionic strength effect, which was 11% for univalent and 28% for alent inorganic ions compared to their limiting ionic mobilities. Additionally, it was possible to determine the limiting ionic mobility for a number of aromatic anions by using PeakMaster 5 to perform an ionic strength correction. A major significance of this work is in being able to use CE to obtain reliable and accurate values of electrophoretic mobilities with all its benefits, including understanding and interpretation of physicochemical phenomena and the ability to model and simulate such phenomena accurately.
Enantiomeric separation of propranolol and selected metabolites by using capillary electrophoresis with hydroxypropyl-β-cyclodextrin as chiral selector
Publisher: Elsevier BV
Date: 1998
DOI: 10.1016/S0021-9673(97)00919-9
Abstract: A capillary electrophoresis (CE) investigation of the enantiomeric separation of propranolol and some of its metabolites using CE was undertaken. Resolution of the enantiomers was achieved using hydroxypropyl-beta-cyclodextrin (HP-beta-CD) as the chiral selector. Parameters found to influence separation include cyclodextrin concentration, potential, pH and organic solvent/additive. It was observed that 17 mM HP-beta-CD gave optimum separation over the concentration range used in this study, however different racemates appear to have best resolution at different CD concentration. The potential does not have a great effect on enantiomer resolution, but appears to cause relative metabolite migration times to alter such that separation is affected. Carrier pH affects both migration time, and enantiomer resolution and metabolite separation. Above pH 5 inferior results are obtained. This is the first report of enantiomeric resolution of propranolol metabolites using CE.
Can volatile organic compounds be markers of sea salt?
Publisher: Elsevier BV
Date: 02-2015
DOI: 10.1016/J.FOODCHEM.2014.07.120
Abstract: Sea salt is a handmade food product that is obtained by evaporation of seawater in saltpans. During the crystallisation process, organic compounds from surroundings can be incorporated into sea salt crystals. The aim of this study is to search for potential volatile markers of sea salt. Thus, sea salts from seven north-east Atlantic Ocean locations (France, Portugal, Continental Spain, Canary Islands, and Cape Verde) were analysed by headspace solid-phase microextraction combined with comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry. A total of 165 compounds were detected, ranging from 32 to 71 compounds per salt. The volatile composition revealed the variability and in iduality of each salt, and a set of ten compounds were detected in all s les. From these, seven are carotenoid-derived compounds that can be associated with the typical natural surroundings of ocean hypersaline environment. These ten compounds are proposed as potential volatile markers of sea salt.
Structure Elucidation Using Gas Chromatography−Infrared Spectroscopy/Mass Spectrometry Supported by Quantum Chemical IR Spectrum Simulations
Publisher: American Chemical Society (ACS)
Date: 11-11-2021
Observations on comprehensive two dimensional gas chromatography coupled with flame photometric detection for sulfur- and phosphorus-containing compounds
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/B9AY00143C
Interactive use of linear retention indices on polar and apolar columns with an MS-library for reliable characterization of australian tea tree and other melaleuca sp. Oils
Publisher: Informa UK Limited
Date: 09-2003
Dynamic interconversion of chiral oxime compounds in gas chromatography
Publisher: Elsevier BV
Date: 02-2010
Multidimensional gas chromatography in food analysis
Publisher: Elsevier BV
Date: 11-2017
Characterization of incense smoke by solid phase microextraction-Comprehensive two-dimensional gas chromatography (GC×GC)
Publisher: Elsevier BV
Date: 09-2007
Nitric oxide metabolites in normal human pregnancy and preeclampsia
Publisher: Informa UK Limited
Date: 1995
Determination of the surface heat-transfer coefficient in CE
Publisher: Wiley
Date: 03-2200
Abstract: A knowledge of the heat-transfer coefficient, h(s), for the external surface of the capillary or the overall heat coefficient, h(OA), is of great value in predicting the mean increase in temperature of the electrolyte, DeltaT(Mean), during electrokinetic separations. For CE, traditional indirect methods of determining h(s) were time-consuming and tended to overestimate cooling efficiency a novel method is introduced, which is based on curve-fitting of plots of conductance versus voltage to calculate several important parameters including DeltaT(Mean), h(s), the conductance free of Joule heating effects (G(0)) and the voltage that causes autothermal runaway, V(lim). The new method is superior to previously published methods in that it can be performed more quickly and that it corrects for systematic errors in the measurement of electric current for voltages <5 kV. These errors tended to exaggerate the cooling efficiency of commercial instruments so that the calculated increases in electrolyte temperature were smaller than their actual values. Axially averaged values for h(s) were determined for three different commercial CE instruments ranging from 164 W m(-2) K(-1) for a passively cooled instrument in a drafty environment to 460 W m(-2) K(-1) for a liquid-cooled instrument.
Capillary gas chromatography and gas chromatography-mass spectrometry of metal(III) and metal(IV) porphyrin complexes
Publisher: Elsevier BV
Date: 11-1982
Enantiomeric separation and quantification of ephedrine-type alkaloids in herbal materials by comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 04-2006
DOI: 10.1016/J.CHROMA.2005.12.043
Abstract: The separation of ephedrine-type alkaloids and their enantiomers in raw herbs and commercial herbal products was investigated by carrying out enantioselective separation in the first-dimension column (containing beta-cyclodextrin as the chiral selector) of a comprehensive two-dimensional gas chromatography (GC x GC) system, whereas a polar polyethylene glycol capillary column was used for separation in the second dimension. Naturally occurring ephedrine-type alkaloids and their synthetic analogues (enantiomeric counterparts) were adequately resolved from each other, as well as from potential interference species in the s le matrix using GC x GC, whereas single column GC analysis was unable to separate all the alkaloids of interest. Detection limits in the order of 0.1-1.3 microg/mL and linearity of calibration with R(2)>or=0.999 over approximately the range of 0.5-100 microg/mL for the quantitative determination of various ephedrine-type alkaloids were obtained. The commercial herbal products tested contained mostly (-)-ephedrine, (+)-pseudoephedrine, (-)-N-methylephedrine and (-)-norephedrine, with concentrations in the range of 40-2100, 0-1,300, 15-300 and 0-30 microg/g of the product, respectively, and repeatability of analysis was generally in the range of 1-5%. The present GCxGC method is effective and useful for the determination of the dosage levels of the principle ephedrine-type alkaloids in commercial health supplements and complex raw herb formulations, as well the differentiation of ephedrine-containing products that were derived from natural plant or synthetic sources, e.g., simply by visualizing the presence or absence of the enantiomeric pairs of (+/-) ephedrine and (+/-)-N-methylephedrine in the GC x GC chromatograms.
Computerised gas chromatographic-mass spectrometric analysis of complex mixtures of alkyl porphyrins
Publisher: Elsevier BV
Date: 1984
DOI: 10.1016/S0021-9673(01)89182-2
Abstract: Computerised capillary gas chromatography-mass spectrometry (GC-MS) analysis of complex mixtures of alkyl porphyrins, as their bis-(trimethylsiloxy)silicon(IV) and bis(tert.-butyldimethylsiloxy)silicon(IV) derivatives, is described. The latter derivative is more suitable for routine GC-MS analysis. This computerised GC-MS approach, when applied to the alkyl porphyrins of two geological s les, a bitumen (Gilsonite, Eocene age, UT, U.S.A.) and a crude oil (Boscan, Cretaceous age, West Venezuela), has revealed the highly complex compositions of these fractions. Computer-aided data processing, using relative retention index (RRI) calculations, facilitated the classification of the chromatographic peaks according to structural type and membership of pseudo-homologous series. Computerised GC-MS is compared with, and contrasted to high-performance liquid chromatography as a means of petroporphyrin analysis.
Second dimension column ensemble pressure tuning in comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 02-2017
DOI: 10.1016/J.CHROMA.2017.10.060
Abstract: A pressure tunable (PT) coupled column ensemble has been implemented for the second dimension (
Evaluation of comprehensive two-dimensional gas chromatography with accurate mass time-of-flight mass spectrometry for the metabolic profiling of plant-fungus interaction in Aquilaria malaccensis
Publisher: Elsevier BV
Date: 03-2015
DOI: 10.1016/J.CHROMA.2015.01.096
Abstract: To explore the possible obligate interactions between the phytopathogenic fungus and Aquilaria malaccensis which result in generation of a complex array of secondary metabolites, we describe a comprehensive two-dimensional gas chromatography (GC × GC) method, coupled to accurate mass time-of-flight mass spectrometry (TOFMS) for the untargeted and comprehensive metabolic profiling of essential oils from naturally infected A. malaccensis trees. A polar/non-polar column configuration was employed, offering an improved separation pattern of components when compared to other column sets. Four different grades of the oils displayed quite different metabolic patterns, suggesting the evolution of a signalling relationship between the host tree (emergence of various phytoalexins) and fungi (activation of biotransformation). In total, ca. 550 peaks/metabolites were detected, of which tentative identification of 155 of these compounds was reported, representing between 20.1% and 53.0% of the total ion count. These are distributed over the chemical families of monoterpenic and sesquiterpenic hydrocarbons, oxygenated monoterpenes and sesquiterpenes (comprised of ketone, aldehyde, oxide, alcohol, lactone, keto-alcohol and diol), norterpenoids, diterpenoids, short chain glycols, carboxylic acids and others. The large number of metabolites detected, combined with the ease with which they are located in the 2D separation space, emphasises the importance of a comprehensive analytical approach for the phytochemical analysis of plant metabolomes. Furthermore, the potential of this methodology in grading agarwood oils by comparing the obtained metabolic profiles (pattern recognition for unique metabolite chemical families) is discussed. The phytocomplexity of the agarwood oils signified the production of a multitude of plant-fungus mediated secondary metabolites as chemical signals for natural ecological communication. To the best of our knowledge, this is the most complete information available so far about essential oils of A. malaccensis, which represents a valuable extension to available data for advanced studies on microbial-mediated biotransformation of terpenes, and offers promise for potential discovery of unanticipated phytochemicals, and biotechnological exploitation.
The combination of gas chromatography-olfactometry and multidimensional gas chromatography for the characterisation of essential oils
Publisher: Elsevier BV
Date: 05-2007
DOI: 10.1016/J.CHROMA.2006.07.019
Abstract: A research area of great interest to the flavour industry is the analysis of odour active compounds in essential oils. In this paper, a methodology is presented for the identification of character-impact odorants in essential oil s les using (a) gas chromatography-olfactometry (GC-O) (b) comprehensive two-dimensional gas chromatography (GC x GC) combined to time-of-flight mass spectrometry (TOFMS) and (c) heart-cut multidimensional gas chromatography-olfactometry (MDGC-O). The specific advantages and limitations of each technique are discussed. The advantage of combining these techniques in a strategy to identify character-impact odorants is demonstrated using ex les from coriander leaf (Coriandrum sativum) and hop (Humulus lupulus) essential oils. In particular, resolution of co-eluting regions of compounds and evaluation of their in idual odour activity is discussed. In coriander leaf, only E-2-dodecenal was found to contribute to a co-eluting odour region, E-2-dodecen-1-ol and 1-dodecanol being present below detection threshold. Using MDGC on a hop essential oil s le, eight significant peaks were resolved from an 18 s heart-cut where a potent odorant was perceived during GC-O.
Two-dimensional retention indices improve component identification in comprehensive two-dimensional gas chromatography of saffron
Publisher: American Chemical Society (ACS)
Date: 15-05-2015
DOI: 10.1021/ACS.ANALCHEM.5B00953
Abstract: Comprehensive two-dimensional gas chromatography hyphenated with accurate mass time-of-flight mass spectrometry (GC × GC-accTOFMS) was applied for improved analytical accuracy of saffron analysis, by using retention indices in the two-dimensional separation. This constitutes 3 dimensions of identification. In addition to accTOFMS specificity, and first dimension retention indices ((1)I), a simple method involving direct multiple injections with stepwise isothermal temperature programming is described for construction of isovolatility curves for reference alkane series in GC × GC. This gives access to calculated second dimension retention indices ((2)I). Reliability of the calculated (2)I was evaluated by using a Grob test mixture, and saturated alkanes, revealing good correlation between previously reported I values from the literature, with R(2) correlation being 0.9997. This essentially recognizes the retention property of peaks in the GC × GC 2D space as being reducible to a retention index in each dimension, which should be a valuable tool supporting identification. The benefit of (2)I data, in supplementing (1)I and MS library matching, was clearly demonstrated by the progressive reduction of the number of possible compound matches for peaks observed in saffron. 114 analytes were assessed according to (1)I and (2)I values within ±20 index unit of reference values, and by MS spectrum matching above a match statistic of 750 (including mass accuracy of the molecular ion <20 ppm) and their possible identities derived. The described method provides a new avenue to utilize the full capability of the two-dimensional separation (GC × GC), in combination with MS library matching in complex s le analysis, to provide improved component identification.
Simultaneous separation of nitrofuran antibiotics and their metabolites by using micellar electrokinetic capillary chromatography
Publisher: Wiley
Date: 10-2006
Abstract: Mixtures comprising nitrofuran antibiotics (NFA) and nitrofuran metabolites (NFM) were resolved for the first time by using MEKC. Sodium deoxycholate (SDC) was chosen as the micelle-forming surfactant. Optimization of separation conditions was achieved by using a central composite experimental design (CCD) approach. Experimental parameters such as concentration ratio of borate to phosphate in the buffer, pH of the running electrolyte and voltage were investigated. The effect of concentration of the surfactant on resolution was significant. Under optimal conditions of 80 mM SDC, pH 9.0, (20 mM borate + 20 mM phosphate) and 16 kV, the resolution between eight consecutive peak pairs ranged from 1.9 to 11.8. Due to the absence of a UV-active chromophore in the metabolites, they were derivatized with 2-nitrobenzaldehyde (2-NBA). In order to mimic a proposed extraction procedure for the analysis of both NFA and/or derivatized NFM in a s le, aqueous s les (prederivatized with 2-NBA) were extracted by using C(18) SPE cartridges. After washing with H(2)O, the cartridges were eluted with a small portion of organic solvent with weak elution characteristics to remove excess 2-NBA (hexane was chosen). Target analytes were then recovered with ACN. Excellent reproducibility of migration time (t(mig)) was achieved for all analytes using the developed MECC approach, with absolute t(mig) <1% RSD and t(mig) ratio <0.2% RSD, and peak area ratio was 4% RSD. The LOD for each compound, calculated by extrapolating to an S/N of 3, were found to be 0.19-2.0 microg/mL.
Phytochemical Constituents and Antiproliferative Activities of Essential Oils from Four Varieties of Malaysian Zingiber officinale Roscoe against Human Cervical Cancer Cell Line
Publisher: MDPI AG
Date: 10-05-2022
Abstract: This study evaluates the volatile metabolic constituents and anticancer potential of essential oils distilled from the rhizomes of four Malaysian Zingiber officinale Roscoe (Zingiberaceae family) varieties (Bentong (BE), Cameron Highlands (CH), Sabah (SA), and Bara (BA)). The ginger essential oils were analyzed by gas chromatography coupled with quadrupole mass spectrometry (GC qMS). A total of 58 secondary compounds were tentatively identified, representing 82.6–87.4% of the total ion count. These metabolites comprise mainly of monoterpene hydrocarbons (19.7–25.5%), oxygenated monoterpenes (23.6–33.7%), sesquiterpene hydrocarbons (21.3–35.6%), oxygenated sesquiterpenes (1.5–3.9%), and other minor classes of compounds (0.7–2.7%). Principal component analysis (PCA) enabled differentiation of the analyzed ginger essential oils according to their varieties, with respect to their metabolites and relative quantities. The antiproliferative activity against the HeLa cervical cancer cell line was investigated via the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The oils were found to exhibit strong antiproliferative activities with IC50 values of 23.8, 35.3, 41.3, and 42.5 μg/mL for BA, BE, SA, and CH, respectively. These findings suggest that the differences among the secondary metabolites and their abundance in different varieties of Z. officinale essential oils appear to be related to their antiproliferative potential. The strong antiproliferative effects of these oils signified their potential in the prevention and chemotherapy of cervical carcinoma treatment.
Techniques and application in comprehensive multidimensional gas chromatography – mass spectrometry
Publisher: Elsevier BV
Date: 2021
Multidimensional chromatographic techniques for monitoring and characterization of environmental samples
Publisher: Springer International Publishing
Date: 2015
Examination of a new chromatographic function, based on an exponential resolution term, for use in optimization strategies: Application to capillary gas chromatography separation of phenols
Publisher: Elsevier BV
Date: 12-1996
Isolating valuable coffee diterpenes by using an inexpensive procedure
Publisher: Elsevier BV
Date: 09-2020
Capillary column gas chromatographic method for the study of dynamic intramolecular interconversion behaviour
Publisher: Elsevier BV
Date: 1988
Multidimensional Capillary Gas Chromatography of Polychlorinated Biphenyl Marker Compounds
Publisher: Wiley
Date: 11-1996
Comprehensive two-dimensional gas chromatography-mass spectrometry analysis of volatile constituents in Thai vetiver root oils obtained by using different extraction methods
Publisher: Wiley
Date: 2010
DOI: 10.1002/PCA.1173
Abstract: Vetiver root oil is known as one of the finest fixatives used in perfumery. This highly complex oil contains more than 200 components, which are mainly sesquiterpene hydrocarbons and their oxygenated derivatives. Since conventional GC-MS has limitation in terms of separation efficiency, the comprehensive two-dimensional GC-MS (GC x GC-MS) was proposed in this study as an alternative technique for the analysis of vetiver oil constituents. To evaluate efficiency of the hyphenated GC x GC-MS technique in terms of separation power and sensitivity prior to identification and quantitation of the volatile constituents in a variety of vetiver root oil s les. METHODOLOGY. Dried roots of Vetiveria zizanioides were subjected to extraction using various conditions of four different methods simultaneous steam distillation, supercritical fluid, microwave-assisted, and Soxhlet extraction. Volatile components in all vetiver root oil s les were separated and identified by GC-MS and GC x GC-MS. The relative contents of volatile constituents in each vetiver oil s le were calculated using the peak volume normalization method. Different techniques of extraction had erse effects on yield, physical and chemical properties of the vetiver root oils obtained. Overall, 64 volatile constituents were identified by GC-MS. Among the 245 well-resolved in idual components obtained by GC x GC-MS, the additional identification of 43 more volatiles was achieved. In comparison with GC-MS, GC x GC-MS showed greater ability to differentiate the quality of essential oils obtained from erse extraction conditions in terms of their volatile compositions and contents.
Enantiomeric analysis of amino acids by using comprehensive two-dimensional gas chromatography
Publisher: Wiley
Date: 2007
DOI: 10.1002/CHIR.20371
Abstract: The chiral separation of amino acids (AA) derivatised with ethyl chloroformate by using comprehensive two-dimensional gas chromatography is reported. A commercially available enantioselective capillary column (Chirasil-l-Val) has been tested as first-dimension column. Two nonenantioselective stationary phases (BPX50 and BP1) with different column lengths were combined with the enantioselective column, which represent chiral olar and chiral/low-polarity column sets, respectively. These column sets were evaluated to determine the most useful column combination to provide improved separation efficiency of enantioselective AA analysis. Separations of AA mixtures derivatised either as their N-trifluoroacetyl methyl esters or with methyl chloroformate, performed on a chiral/low-polarity column set, are also shown. The method was demonstrated for chiral analysis of AAs in different beer s les. The major AA in the beer s les was proline with amounts ranging from around 65-95% with minor contents of glycine and the l-enantiomers of alanine, valine, leucine, and isoleucine. Small amounts of d-alanine, at about 1, 1.5, and 15% were detected in the three s les.
Quantification of polycyclic aromatic hydrocarbons based on comprehensive two-dimensional gas chromatography-isotope dilution mass spectrometry
Publisher: Elsevier BV
Date: 08-2008
DOI: 10.1016/J.CHROMA.2008.06.028
Abstract: Comprehensive two-dimensional gas chromatography (GCxGC) offers favourable resolution and sensitivity compared with conventional one-dimensional gas chromatography (1D-GC), as reported in many studies. These characteristics are of major interest when analytes are in trace concentration, and are present in complex mixtures, as is the case of polycyclic aromatic hydrocarbons (PAHs) in atmospheric particulate s les. Whilst GCxGC has been widely applied to identification of different types of analytes in several matrices, less seldom has it been used for quantification of these analytes. Although several quantitative methods have been proposed, they may be tedious and/or require considerable user development. Whereas quantification in 1D-GC is a routine and well-established procedure, in GCxGC, it is not so straightforward, especially where novel or untested procedures have yet to be incorporated into software packages. In the present study, it is proposed that a subset of the modulated peaks generated for each solute may be summed, based on the specific target ion mass of each compound present in a certified standard reference material (SRM) 1649a (urban dust). The ratio between a PAH and its corresponding deuterated (PAH-d) form showed that there is no statistical loss of sensitivity when this ratio is calculated based on whether the total sum of modulated peaks, or if only the two or the three most intense modulated peaks, are employed. Manual integration may be required, and here was found to give more acceptable values than automatic integration. Automated integration has been shown here to underestimate the modulated peak responses when low concentrations of PAHs were analyzed. Although for most PAHs good agreement with the certified values were observed, the analytical method needs to be further optimized for some of the other PAH, as can be see with those PAH with high variability in the range of urban dust analyzed.
Improvement of safflower oil quality for biodiesel production by integrated application of PGPR under reduced amount of NP fertilizers
Publisher: Public Library of Science (PLoS)
Date: 10-08-2018
Comprehensive two-dimensional gas chromatography
Publisher: Springer Science and Business Media LLC
Date: 05-2003
Investigation of the Thermal Oxidation of Conventional and Alternate Aviation Fuels with Comprehensive Two-Dimensional Gas Chromatography Accurate Mass Quadrupole Time-of-Flight Mass Spectrometry
Publisher: American Chemical Society (ACS)
Date: 20-04-2017
Determination of Enantiomeric Distribution of Terpenes for Quality Assessment of Australian Tea Tree Oil
Publisher: American Chemical Society (ACS)
Date: 06-06-2016
Abstract: A number of papers have appeared in recent years proposing the use of enantiomeric ratios of key monoterpenes in Australian tea tree oil (TTO) for detection of adulterated oils. There are however a range of reported values, even from exactly the same suite of authentic oils, and we address here probable reasons for these differences and stress the importance of establishing reference ratios within each laboratory based on oils of known provenance. Any biological variation in the ratio for the key terpene terpinen-4-ol has been demonstrated to be effectively unmeasurable, because the standard deviation on multiple measurements of the same oil is of the same order as that of multiple authentic oils.
Studies on Cryogenic Trapping of Solutes during Chromatographic Elution in Capillary Gas Chromatography
Publisher: Wiley
Date: 07-1996
Simultaneous deconvolution and re-construction of primary and secondary overlapping peak clusters in comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 04-2011
DOI: 10.1016/J.CHROMA.2011.02.028
Abstract: In this study, simultaneous deconvolution and reconstruction of peak profiles in the first ((1)D) and second dimension ((2)D) of comprehensive two-dimensional (2D) gas chromatography (GC×GC) is achieved on the basis of the property of this new type of instrumental data. First, selective information, where only one component contributes to the peak elution window of a given modulation event, is employed for stepwise stripping of each (2)D peak with the help of pure components corresponding to that compound from the neighbouring modulations. Simulation based on an exponentially modified Gaussian (EMG) model aids this process, where the EMG represents the envelope of all (2)D peaks for that compound. The peak parameters can be restricted by knowledge of the pure modulated (2)D GC peaks derived from the same primary compound, since it is modulated into several fractions during the trapping and re-focusing process of the cryogenic modulation system according to the modulation period. Next, relative areas of all pure (2)D components of that compound are considered for reconstruction of the primary peak. This strategy of exploitation of the additional information provided by the second dimension of separation allows effective deconvolution of GC×GC datasets. Non-linear least squares curve fitting (NLLSCF) allows the resolved 2D chromatograms to be recovered. Accurate acquisition of the pure profiles in both (1)D and (2)D aids quantification of compositions and prediction of 2D retention parameters, which are of interest for qualitative and quantitative analysis. The ratio between the sum of squares of deconvolution residual and original peak response (R(rr)) is employed as an effective index to evaluate the resolution results. In this work, simulated and experimental ex les are used to develop and test the proposed approach. Satisfactory performance for these studies is validated by minimum and maximum R(rr) values of 1.34e-7% and 1.09e-2% and 1.0e-3% and 3.0e-1% for deconvolution of (1)D and (2)D peaks, respectively. Results suggest that the present technique is suitable for GC×GC data processing.
Separation Multidimensionality for Improved Sample Characterization—Is It Worth the Effort?
Publisher: American Chemical Society (ACS)
Date: 23-09-2021
Cryogenic trapping as a versatile approach for sample handling, enrichment and multidimensional analysis in gas chromatography
Publisher: Elsevier BV
Date: 05-2021
Development of an algorithm for peak detection in comprehensive two-dimensional chromatography
Publisher: Elsevier BV
Date: 07-2007
DOI: 10.1016/J.CHROMA.2006.10.066
Abstract: A method for peak detection in two-dimensional chromatography is presented. The algorithm applies first the methods developed for peak detection in one-dimensional chromatography to detect peaks in one dimension. In a second step, a decision tree is applied to decide which one-dimensional peaks are originated from the same compound and have to be 'merged' into one two-dimensional peak. To this end, different features of the peaks (second-dimension peak regions and second-dimension retention times) are compared and different criteria (common peak regions, retention time differences, unimodality in the first dimension) are applied. Different options can be used, depending on the nature of the data. The user controls this decision tree by establishing several options and "switches". The algorithm was tested with GCxGC chromatograms obtained for a commercial air-freshener s le, detecting and merging the modulated peaks belonging to the same compound. Recommendations for the set of options and switches are given. A utility that calculates and sums peak areas from merged peaks is added to facilitate automated quantification. Although the algorithm was developed for GCxGC, its application to comprehensive two-dimensional liquid chromatography (LCxLC) data should at most require minor modifications.
Peak modeling approach to accurate assignment of first-dimension retention times in comprehensive two-dimensional chromatography
Publisher: American Chemical Society (ACS)
Date: 23-07-2009
DOI: 10.1021/AC900960N
Abstract: Modeling of first-dimension retention of peaks based on modulation phase and period allows reliable prediction of the modulated peak distributions generated in the comprehensive two-dimensional chromatography experiment. By application of the inverse process, it is also possible to use the profile of the modulated peaks (their heights or areas) to predict the shape and parameters of the original input chromatographic band (retention time, standard deviation, area) for the primary column dimension. This allows an accurate derivation of the first-dimension retention time (RSD 0.02%) which is equal to that for the non-modulated experiment, rather than relying upon the retention time of the major modulated peak generated by the modulation process (RSD 0.16%). The latter metric can produce a retention time that differs by at least the modulation period employed in the experiment, which displays a discontinuity in the retention time vs modulation phase plot at the point of the 180 degrees out-of-phase modulation. In contrast, the new procedure proposed here gives a result that is essentially independent of modulation phase and period. This permits an accurate value to be assigned to the first-dimension retention. The proposed metric accounts for the time on the second-dimension, the phase of the distribution, and the hold-up time that the s led solute is retained in the modulating interface. The approach may also be based on the largest three modulated peaks, rather than all modulated peaks. This simplifies the task of assigning the retention time with little loss of precision in band standard deviation or retention time, provided that these peaks are not all overloaded in the first or second dimension.
Characterization of biodiesel and biodiesel blends using comprehensive two-dimensional gas chromatography
Publisher: Wiley
Date: 08-2008
Abstract: In this work the development of a comprehensive 2-D GC flame ionization detection (GC x GC FID) method for biodiesel fuels is reported. This method is used for the analysis of fatty acid methyl esters (FAMEs) in both biodiesel (B100) and biodiesel blend (B5) s les. The separation of FAME was based on component boiling point in the first dimension and polarity in the second dimension by using a BPX5/BP20 column set to provide a measure of 'orthogonality' in the 2-D space. Here the columns are coupled with a cryogenic modulator operating in a novel temperature programmed mode (T(M)) whereby the cryotrap is progressively incremented in temperature as the oven temperature is increased. The final method employs eight cryotrap temperature settings. The developed GC x GC method is able to successfully characterize and identify both B100 and B5 FAME components, which are produced from a variety of vegetable oils, animal fats and waste cooking oils, with high precision. The method is capable of analysing FAME with carbon numbers C4-C24, and is particularly suitable to characterize various types of biodiesel, making it possible to differentiate the origin and type of FAME used in the biodiesel s les.
Multidimensional gas chromatography
Publisher: Elsevier BV
Date: 04-2012
A modeling approach for orthogonality of comprehensive two-dimensional separations
Publisher: American Chemical Society (ACS)
Date: 17-06-2013
DOI: 10.1021/AC400736V
Abstract: A novel method is developed for orthogonality evaluation of comprehensive two-dimensional separations (C2DS). Utilization of efficiency measures such as peak capacity (n(c)) can be critically evaluated for C2DS analysis to describe an orthogonal separation of the analytes in a 2D plane. Unlike most previous methods focusing on "bin coverage" over 2D space, rather than taking into account the distribution based on accurate peak retention, in the proposed method, the separation orthogonality of C2DS is ided into two parts (i.e., C(pert) and C(peaks)). These correspond to peak coverage percent, and 2D distribution correlation of compounds, respectively. Bin occupation and a simple-linear regression model, on the basis of normalized retention times in 2D separation space ((1)t(R) and (2)t(R)), are further introduced to quantitatively define the two terms. Orthogonality ranges from 0 to 1 correspond to perfectly correlated and orthogonal separations, respectively, which are presented based on both C(pert) and C(peaks) considerations. The advantage of this method is the use of separation properties of C2DS to characterize practical 2D peak distribution and does not rely on assumptions or any imposed limitations. Simulation of comprehensive two-dimensional gas chromatography (GC × GC) was achieved by using the Abraham solvation parameter model, and applied to generate ex les for orthogonality assessment. In this work, 225 compounds comprising a range of chemical classes were simulated for separation on two column set pairs comprising low polarity olar and moderately polar olar combinations. Results illustrate that the proposed method applied to GC × GC provides a reasonable assessment of 2D separation performance and may be used to derive optimal experimental conditions when used with an experimental design strategy.
Comprehensive two-dimensional gas chromatography (GC × GC) and GC × GC-quadrupole MS analysis of Asian and American ginseng
Publisher: Wiley
Date: 08-2003
Abstract: Extracts of the roots of Panax (ginseng) species are analysed using comprehensive two‐dimensional gas chromatography. Comparison of comprehensive two‐dimensional chromatograms reveals the presence of numerous common components, and possible species‐specific components are also observed. Two‐dimensional bubble plot presentations of GC×GC(FID) data allow ready qualitative and semi‐quantitative comparison of the extracts. The use of GC×GC‐quadrupole MS (GC×GC‐qMS), operated at a scanning rate of 20 Hz, in conjunction with retention data, permits identification of separated (major) components. Whilst this scan speed will be insufficient for reliable quantitative analysis, considerably improved quality of uncorrected spectra, arising from the enhanced separation over single column GC‐MS analysis is apparent. Spectral match qualities of up to 99% are found for a number of components. Comparison of GC×GC‐qMS with GC×GC(FID) indicates that good correspondence of peak position patterns is achieved, which aids component identification. It is shown that (quadrupole) mass spectrometric detection is a useful tool for provision of identification of separated compounds in high‐resolution comprehensive two‐dimensional gas chromatography.
Comprehensive two-dimensional liquid chromatography for polyphenol analysis in foodstuffs
Publisher: Wiley
Date: 16-09-2017
Abstract: Polyphenols are a class of plant secondary metabolites that are recently drawing a special interest because of their broad spectrum of pharmacological effects. As they are characterized by an enormous structural variability, the identification of these molecules in food s les is a difficult task, and sometimes having only a limited number of commercially available reference materials is not of great help. One-dimensional liquid chromatography is the most widely applied analytical approach for their analysis. In particular, the hyphenation of liquid chromatography to mass spectrometry has come to play an influential role by allowing relatively fast tentative identification and accurate quantification of polyphenolic compounds at trace levels in vegetable media. However, when dealing with very complex real-world food s les, a single separation system often does not provide sufficient resolving power for attaining rewarding results. Comprehensive two-dimensional liquid chromatography is a technique of great analytical impact, since it offers much higher peak capacities than separations in a single dimension. In the present review, we describe applications in the field of comprehensive two-dimensional liquid chromatography for polyphenol analysis in real-world food s les. Comprehensive two-dimensional liquid chromatography applications to nonfood matrices fall outside the scope of the current report and will not be discussed.
Gas chromatography/mass spectrometry-based metabolic profiling and differentiation of Ginseng roots according to cultivation age using variable selection
Publisher: Oxford University Press (OUP)
Date: 11-2013
Abstract: Ginseng roots are an important herbal resource worldwide, and the adulteration of ginseng with age is recognized as a serious problem. It is therefore crucial to develop objective criteria or standard protocols for differentiating ginseng root s les according to their cultivation age. The reported study used GC/MS combined with multivariate statistical analysis with variable selection to obtain metabolic profiling and an optimal partial least squares-discriminant analysis (PLS-DA) model for the differentiation of ginseng according to cultivation age. Relative levels of various metabolites, such as amino acids, alcohols, fatty acids, organic acids, and sugars, were measured for various ginseng cultivation ages. Increasing cultivation age resulted in the production of higher levels of panaxynol and panaxydol, which are active polyacetylene compounds in ginseng. In addition, optimized PLS-DA models for the prediction of ginseng age were obtained by selecting variables based on a variable importance in the projection cut-off value of 1.3. Proline, glucaric acid, mannose, gluconic acid, glucuronic acid, myoinositol, panaxydol, and panaxynol are suggested as key and relevant compounds with which to differentiate the age of ginseng s les. The findings of this study suggest that GC/MS-based metabolic profiling can be used to differentiate ginseng s les according to cultivation age.
Cryogenic solute manipulation in gas chromatography - The longitudinal modulation approach
Publisher: Elsevier BV
Date: 02-1999
Identification of character impact odorants in coriander and wild coriander leaves using GC-olfactometry and GC x GC-TOFMS
Publisher: Elsevier
Date: 2006
Chromatography in the third world and in the first world
Publisher: Wiley
Date: 11-0003
Molecular spectroscopy – Information rich detection for gas chromatography
Publisher: Elsevier BV
Date: 02-2018
Some Characteristics of a Flame Photometric Detector in Sulphur and Phosphorus Modes
Publisher: Oxford University Press (OUP)
Date: 02-1982
Quality and antioxidant properties of instant noodles enhanced with common buckwheat flour
Publisher: Elsevier BV
Date: 05-2013
Exploring thermal isomerisation in gas chromatography analyses using natural pyrethrins: Comparison of comprehensive two-dimensional and one-dimensional gas chromatography
Publisher: Elsevier BV
Date: 10-2023
Capillary gas chromatography of metal-porphyrin complexes
Publisher: Elsevier BV
Date: 02-1982
Comprehensive two‐dimensional gas chromatography for the separation of fatty acids in milk
Publisher: Wiley
Date: 08-2007
A review of environmental toxicant analysis by using multidimensional gas chromatography and comprehensive GC
Publisher: Elsevier BV
Date: 02-2003
DOI: 10.1016/S0009-8981(02)00382-0
Abstract: The purpose of this review is to highlight the developments in coupled-column gas chromatography methods for qualitative analysis of selected environmental toxicants such as dioxin, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), etc. In particular, the new technique of GC x GC will be introduced, and its role, and the promise it offers to this field is discussed. The benefits of enhanced separation to quantitative analysis will be considered. In order to perform an accurate risk assessment, both the dose and biological effects of environmental toxicants have to be determined with a high degree of certainty. This is most often achieved by using chromatographic methods. Given the complexity of most environmental s le extracts, single-column gas chromatography is unable to fully resolve all the components of interest frequently leading to a positive bias in the reported concentrations. Advanced separation tools, such as multidimensional gas chromatography (MDGC), were investigated quite early and demonstrated improvements in separation. However, limitations in the number of target analytes that could be analyzed in a single run as well as insufficient robustness lead to a continued interest in alternative solutions. The parallel development of mass spectrometric identification and quantification strategies proved useful in many cases, although it frequently failed to provide positive identification of chromatographically unresolved isomeric compounds. More recently, comprehensive two-dimensional gas chromatography (GC x GC) may offer a solution to that problem, especially because it offers enhanced resolution for complex mixtures containing trace level environmental toxicants.
Pressure Tuning of First Dimension Columns in Comprehensive Two-Dimensional Gas Chromatography
Publisher: American Chemical Society (ACS)
Date: 29-08-2016
DOI: 10.1021/ACS.ANALCHEM.6B02017
Abstract: The experimental approach and mechanism of pressure tuning (PT) are introduced for the first stage of a comprehensive two-dimensional gas chromatography (GC × GC) separation. The PT-GC × GC system incorporates a first dimension ((1)D) coupled column ensemble comprising a pair of (1)D columns ((1)D1 and (1)D2) connected via a microfluidic splitter device, allowing variable decompression of carrier gas across each (1)D column, and a conventional (2)D narrow bore column. By variation of junction pressure between the (1)D1 and (1)D2 columns, tunable total (1)D retentions of analytes are readily derived. Separations of a standard mixture comprising a number of different chemical classes (including alkanes, monoaromatics, alcohols, aldehydes, ketones, and esters) and Australian tea tree oil (TTO) were studied as practical ex les of the PT-GC × GC system application. This illustrated the change of analyte retention time with experimental conditions depending on void time and retention on the different columns. In addition to void time change, variation of carrier gas relative decompression in the (1)D ensemble leads to tunable contribution of the (1)D1/(1)D2 columns that changes apparent polarity and selectivity of the ensemble. The resulting changes in (1)D elution order further altered elution temperature and thus retention of each analyte on the (2)D column in temperature-programmed GC × GC. 2D orthogonality measurements were then conducted to evaluate overall separation performance under application of different (1)D junction pressure. As a result, distribution and selectivity of particular target compounds, monoterpenes, sesquiterpenes, and oxygenated terpenes in 2D space, and thus orthogonality, could be adequately tuned. This indicates the potential of PT-GC × GC to be applicable for practical s le separation and provides a general approach to tune selectivity of target compounds.
Relating pressure tuned coupled column ensembles with the solvation parameter model for tunable selectivity in gas chromatography
Publisher: Elsevier BV
Date: 07-2016
DOI: 10.1016/J.CHROMA.2016.05.092
Abstract: The differential pressure drop of carrier gas by tuning the junction point pressure of a coupled column gas chromatographic system leads to a unique selectivity of the overall separation, which can be tested using a mixture of compounds with a wide range of polarity. This study demonstrates a pressure tuning (PT) GC system employing a microfluidic Deans switch located at the mid-point of the two capillary columns. This PT system allowed variations of inlet-outlet pressure differences of the two columns in a range of 52-17psi for the upstream column and 31-11psi for the downstream column. Peak shifting (differential migration) of compounds due to PT difference are related to a first order regression equation in a Plackett-Burman factorial study. Increased first (upstream) column pressure drop makes the second column characteristics more significant in the coupled column retention behavior, and conversely increased second (downstream) column pressure drop makes the first column characteristics more apparent such variation can result in component swapping between polar and non-polar compounds. The coupled column system selectivity was evaluated in terms of linear solvation energy relationship (LSER) parameters, and their relation with different pressure drop effects has been constructed by applying multivariate principle component analysis (PCA). It has been found that the coupled column PT system descriptors provide a result that shows a clear clustering of different pressure settings, somewhat intermediate between those of the two commercial columns. This is equivalent to that obtained from a conventional single-column GC analysis where the interaction energy contributed from the stationary phases can be significantly adjusted by choice of midpoint PT. This result provides a foundation for pressure differentiation for selectivity enhancement.
Modulation and Manipulation of Gas Chromatographic Bands by Using Novel Thermal Means
Publisher: Springer Science and Business Media LLC
Date: 08-1998
Comprehensive multidimensional separations
Publisher: Springer Science and Business Media LLC
Date: 16-09-2011
One- and comprehensive two-dimensional high-performance liquid chromatography analysis of alkylphenol polyethoxylates
Publisher: Wiley
Date: 14-11-2011
Abstract: High-performance liquid chromatography (HPLC) analysis of alkylphenol polyethoxylates (APnEOs) in one-dimensional (1-D) mode usually separates either the ethoxy or alkyl moiety distribution and requires different modes for adequate resolution. Simultaneous complete separation of variable ethoxymer chain lengths and variable alkyl end groups using 1-D-HPLC has not been reported and suggests that multidimensional (MDLC) or comprehensive two-dimensional liquid chromatography (LC×LC) might offer a suitable separation approach for this goal. This study compares different separation modes--normal phase LC (NPLC), reversed-phase LC (RPLC) and hydrophilic interaction chromatography (HILIC)--in terms of separation for alkyl and ethoxy distributions. RPLC provided adequate separation of octyl and nonyl APnEOs using an isocratic elution program and was selected as second dimension ((2)D) for LC×LC. NPLC offered better resolution than HILIC however, non-polar NPLC solvent immiscibility with RPLC mobile phases leads to HILIC being chosen as first dimension ((1)D). The HILIC×RPLC system was evaluated by analysis of four APnEO mixtures. Complete simultaneous separation of APnEOs into in idual oligomers, with each alkyl end group resolved, demonstrated the capability of the LC×LC method. Different descriptors and metrics for assessing system orthogonality were investigated to evaluate HILIC×RPLC performance. A relatively high dimensionality of 1.76 was demonstrated.
Comprehensive two-dimensional gas chromatography-mass spectrometry analysis and comparison of volatile organic compounds in Brazilian cachaça and selected spirits
Publisher: Elsevier BV
Date: 02-2009
Gas chromatography–Fourier transform infrared spectroscopy reveals dynamic molecular interconversion of oximes
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9AN00990F
Abstract: Oxime E / Z isomers interconvert on GC columns they can be in idually monitored using FTIR to provide profiles of each isomer.
Generating multiple independent retention index data in dual-secondary column comprehensive two-dimensional gas chromatography
Publisher: American Chemical Society (ACS)
Date: 31-10-2006
DOI: 10.1021/AC060869L
Abstract: A method producing simultaneously three retention indexes for compounds has been developed for comprehensive two-dimensional gas chromatography by using a dual secondary column approach (GC x 2GC). For this purpose, the primary flow of the first dimension column was equally erted into two secondary microbore columns of identical geometry by means of a three-way flow splitter positioned after the longitudinally modulated cryogenic system. This configuration produced a pair of comprehensive two-dimensional chromatograms and generated retention data on three different stationary phases in a single run. First dimension retention indexes were determined on a polar SolGel-Wax column under linear programmed-temperature conditions according to the van den Dool approach using primary alcohol homologues as the reference scale. Calculation of pseudoisothermal retention indexes in both second dimensions was performed on low-polarity 5% phenyl equivalent polysilphenylene/siloxane (BPX5) and 14% cyanopropylphenyl/86% dimethylpolysiloxane (BP10) columns. To construct a retention correlation map in the second dimension separation space upon which KovAts indexes can be derived, two methods exploiting "isovolatility" relationships of alkanes were developed. The first involved 15 sequential headspace s lings of selected n-alkanes by solid-phase microextraction (SPME), with each s ling followed by their injection into the GC at predetermined times during the chromatographic run. The second method extended the second dimension retention map and consisted of repetitive introduction of SPME-s led alkane mixtures at various isothermal conditions incremented over the temperature program range. Calculated second dimension retention indexes were compared with experimental values obtained in conventional one-dimensional GC. A case study mixture including 24 suspected allergens (i.e., fragrance ingredients) was used to demonstrate the feasibility and potential of retention index information in comprehensive 2D-GC.
Miniaturized molecularly imprinted polymer extraction method for the gas chromatographic analysis of flavonoids
Publisher: Wiley
Date: 05-03-2202
Abstract: In this study, the use of monolithic molecularly imprinted polymers in a micropipette tip format allowing the simple and fast extraction of flavonoids from standard solutions and a black tea s le is demonstrated. The imprinted polymer employed quercetin, methacrylic acid or 4-vinylpyridine, and ethylene glycol dimethacrylate as template, functional monomer, and cross-linker, respectively. Surface morphologies of the quercetin-imprinted polymers and the corresponding nonimprinted polymers were characterized by SEM. Extraction of flavonoid standards was performed to evaluate the selectivity and recovery with these imprinted and nonimprinted polymers. Flavonoid compositions in aliquots eluted from the tips were identified using fast GC with flame ionization detection. Maximum specific capacities of 0.2, 5.7, and 16.0 mg/g for catechin, morin, and quercetin, respectively, were obtained with the imprinted polymer prepared with methacrylic acid, with the corresponding recoveries of 99.8, 98.8, and 95.4%, respectively. Efficient extraction by the quercetin-imprinted polymer of epicatechin, catechin, and quercetin from an apple-flavored black tea s le was achieved, with GC-MS employed for compound identification for both the tea and extracted s les.
Gas chromatographic technologies for the analysis of essential oils
Publisher: Elsevier BV
Date: 11-2001
DOI: 10.1016/S0021-9673(01)01314-0
Abstract: Essential oil analysis has basically had one technical goal: to achieve the best possible separation performance by using the most effective, available technology of the day. The result achieved from this may then be used to answer the research or industrial analysis questions which necessitated the analysis. This may be for comparative purposes, where one oil is contrasted with other(s) for quality control or investigation of adulteration, to discover new components, or to characterise the chemical classes of compounds present. Clearly, today the analyst turns to chromatography as the provider of separation and then may supplement that with mass spectrometry to aid identification. The power of GC-MS means that advances in both the separation technique, and improvements in mass spectrometry detection - along with improved data handling tools - will immediately be relevant to the essential oil area. This present review outlines the developmental nature of instrumental approaches to essential oil analysis using gas chromatography. Mass spectrometry will be included to the extent that it represents the hyphenation of choice for most analysts when analysing essential oils. Thus single-column and multi-dimensional analysis will be covered, as will s le handling or introduction techniques prior to the analysis step, where these techniques provide some measure of separation. The recent demonstration of comprehensive gas chromatography will be discussed as the potentially most powerful separation method for essential oils. This brief review is not intended to be a comprehensive dissertation on the field of essential oil analysis since that would require sufficient space to occupy a book in its own right. Rather, it will outline selected considerations and developments, to help explain where new technology has been applied to advantage in this field.
Person-portable gas chromatography-toroidal ion trap mass spectrometry analysis of coffee bean volatile organic compounds
Publisher: Elsevier BV
Date: 03-2022
Sequential Hybrid Three-Dimensional Gas Chromatography with Accurate Mass Spectrometry: A Novel Tool for High-Resolution Characterization of Multicomponent Samples
Publisher: American Chemical Society (ACS)
Date: 26-03-2018
DOI: 10.1021/ACS.ANALCHEM.8B00142
Abstract: A novel sequential three-dimensional gas chromatography-high-resolution time-of-flight mass spectrometry (3D GC-accTOFMS) approach for profiling secondary metabolites in complex plant extracts is described. This integrated system incorporates a nonpolar first-dimension (
Evaluation of quadrupole-time-of-flight mass spectrometry in comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 10-2014
DOI: 10.1016/J.CHROMA.2014.08.053
Abstract: Quadrupole time-of-flight mass spectrometry (Q-TOFMS) has been evaluated with respect to its applicability in comprehensive two-dimensional gas chromatography (GC×GC). At a maximum acquisition frequency, while approximately 50 full accurate mass spectra on disk were acquired per s (50Hz) in scan mode, the s ling rate in target mode (MS/MS) was strongly dependent on the number of target ions selected. The number of selected precursor ions per time window proportionally decreased the acquisition rate for each ion one precursor ion ≅31.35Hz two ions ≅16.68Hz and for 8 precursor ions, a s ling rate of just 4.18Hz was found. When Q-TOFMS was used in simultaneous mode, where in addition to the acquisition of target ion MS/MS signals, it also collects the full mass spectrum, s ling rates were even lower. It is demonstrated that Q-TOFMS generates sufficient data points over each peak in GC×GC operation in scan mode using TOFMS acquisition only, or is able to collect sufficient data points for relatively wide chromatographic peaks (≥600ms) in the target mode (MS/MS), however only if one or two precursor ions are selected per time window. Mass accuracy was found to perform within specification (<5ppm), even for the fastest acquisition operation (50Hz). Spectral deconvolution is demonstrated to work better in GC×GC than in 1D GC mode. Data visualisation in target GC×GC mode presents difficulties when there are overlapping target windows comprising different numbers of precursor ions.
Retention indices in comprehensive two-dimensional gas chromatography
Publisher: Springer Science and Business Media LLC
Date: 09-08-2011
DOI: 10.1007/S00216-011-5247-1
Abstract: The identification of compounds by using gas chromatography (GC) in s les with significant complexity comprising a range of isomeric species, where characterization is based on peak retention times and mass spectra, generates uncertainty for the analyst. This leads to identification errors. The most reliable way to confirm the identification of each compound is based on authentic standard co-injection, which in several cases is economically prohibitive, and often unachievable in the time available for analysis. Retention index procedures are important tools to minimize misidentification of compounds in conventional chromatography. The introduction of comprehensive two-dimensional GC (GC × GC) for analysis of complex s les was a decisive step to increase the analytical capacity of chromatographic techniques. For many s les, the chromatographic resolution increase leads to quantitative expansion in the number of peaks identified, compared with conventional GC analysis. Notwithstanding this improved resolution, limitations still persist in correct peak identification, which suggests the use of retention indices may assist in supporting component identification in this important technique. In this work, approaches to use of the retention index in GC × GC are discussed, based on an evaluation of the literature in this area. Interpretation of effective chain length data for fatty acid methyl esters in the first and second dimensions is presented.
Enantioselective gas chromatographic analysis of monoterpenes in essential oils of the family Myrtaceae
Publisher: Wiley
Date: 2004
DOI: 10.1002/FFJ.1368
Aroma-impact compounds in dried spice as a quality index using solid phase microextraction with olfactometry and comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 12-2013
DOI: 10.1016/J.FOODCHEM.2013.05.156
Abstract: A systematic experimental procedure is used to identify the aroma-impact compounds, leading to a shelf quality index based on head space solid-phase microextraction. Dried (ground) fennel seeds, having shelf life of 6 months (0.5Y) and 5 years (5Y), were used as a spice model for assessment of comparative aroma quality. Aroma-impact odorants were analysed by GC-olfactometry (GC-O) in parallel with comprehensive two-dimensional GC-flame ionisation detection (GC×GC-FID) using a polar/non-polar phase combination for the GC×GC column set. Tentative identification of aroma-impact odorants involved correlating data from the GC-O/FID system with GC×GC-time-of-flight mass spectrometry analysis by means of retention indices. Major compounds responsible for aroma perception were limonene, 1,8-cineole, terpinen-4-ol, estragole and trans-anethole, and showed an average decrease of 30-50% NIF from 0.5Y to 5Y. Monoterpenes which represent 'freshness', e.g. β-pinene and β-myrcene, exhibited identifiable aroma-impact only for the 0.5Y product. Sesquiterpenes and sesquiterpene oxides are suggested as an aging index, being present in increased amounts in 5Y. p-Anisaldehyde odour intensity for both s les remained the same (aroma perception sweet creamy, floral odour and Chinese seasoning powder).
Automated method using direct-immersion solid-phase microextraction and on-fiber derivatization coupled with comprehensive two-dimensional gas chromatography high-resolution mass spectrometry for profiling naphthenic acids in produced water
Publisher: Elsevier BV
Date: 03-2023
Time-resolved cryogenic modulation reveals isomer interconversion profiles in dynamic chromatography
Publisher: Elsevier BV
Date: 06-2001
DOI: 10.1016/S0021-9673(01)00778-6
Abstract: The dynamic chromatographic study of interconversion of E and Z forms of oximes has been investigated by using a novel cryogenic modulation method in a two-dimensional gas chromatographic array. The primary column is a conventional capillary GC column on which the molecular interconversion proceeds. In this case, the molecular dynamical process leads to a peak profile describing the kinetics and thermodynamics of the interconverting molecules during its chromatographic elution. Thus an interconversion region intercedes the elution of the in idual stereoisomers of the reaction. Since the molecules are isomers, classical molecular identification methods such as gas chromatography-mass spectrometry are unable to study the in idual instantaneous amounts of each of the compounds. Hence the infinitesimal profiles of interconversion along the entire column have never been experimentally observed rather the total profile is normally subjected to mathematical modelling studies in order to match experiment with theory, and to gain the kinetic parameters of the process. In the present study, an instantaneous ratio of the in idual isomers can be found during the chromatographic elution by direct measurement. This is achieved by using a cryogenic zone focussing process, with rapid longitudinal modulation of a cold trap and continual pulsing of collected zones into a fast-analysis high-resolution capillary column on which isomer interconversion is minimized. The data can be displayed as a two-dimensional contour plot to demonstrate the in idual isomer profiles. The two-dimensional analysis also allows easy measurement of the peak ratios of the two isomers which is an indicator of the extent of interconversion that has taken place. Two model systems, acetaldoxime and butyraldoxime, were chosen to illustrate the use of the cryogenic modulation procedure. It is anticipated that the procedure could be applied to other molecules which exhibit gas-phase isomerizations or reactions.
Pressurised liquid extraction-comprehensive two-dimensional gas chromatography for fast-screening of polycyclic aromatic hydrocarbons in soil
Publisher: Elsevier BV
Date: 11-2003
DOI: 10.1016/J.CHROMA.2003.07.006
Abstract: Pressurised liquid extraction (PLE) was applied to the extraction of polycyclic aromatic hydrocarbons (PAHs) from contaminated soils from Husarviken in Stockholm, Sweden. The extraction step was followed by conventional gas chromatography (GC), comprehensive two-dimensional gas chromatography (GC x GC) (both with flame ionisation detection) and gas chromatography-quadrupole mass spectrometry (GC-MS) analysis. Qualitative and quantitative aspects of the results are considered. Qualitatively, results from all chromatographic analyses are in good agreement, and PLE provides a reliable extraction technique with all PAHs extracted in one extraction step no carry over was observed. With respect to PAH quantification, some variability in results was noted, with better agreement in PAH concentrations for GC and GC x GC measurement, as compared to GC-MS. GC analysis compares favourably with GC x GC apart from the few exceptions where peaks are not fully resolved from other co-extracted analytes, which compromises GC-FID measurement. For ex le, acenaphthene shows a much higher concentration when measured by GC-FID, demonstrating the superior separating powers of GC x GC the latter is the preferred technique if precise and accurate quantification of analytes are required. GC-MS results compare reasonably with GC x GC for low-molecular mass PAHs but not for high-molecular mass PAHs results for GC-MS are consistently higher than those for GC x GC for high-molecular mass PAHs. Since PLE-GC x GC is proposed as a broad screening tool, the demand for precise quantification may be relaxed in the present situation. GC x GC has the added advantage of providing chemical structural information within the two-dimensional contour presentation. Reproducibilities for GC x GC results (peak area) and 2tR were acceptable with relative standard deviations (R.S.D.) of 8 and 1%, respectively (at the mg/kg level), and good repeatability within s les was achieved.
Use and abuse of retention indices in gas chromatography
Publisher: Elsevier BV
Date: 10-2023
Variation of wine preference amongst consumers is influenced by the composition of salivary proteins
Publisher: Springer Science and Business Media LLC
Date: 16-09-2023
Analysis of methoxypyrazines in wine using headspace solid phase microextraction with isotope dilution and comprehensive two-dimensional gas chromatography
Publisher: Wiley
Date: 06-2005
Abstract: This study reports an optimized headspace‐solid phase microextraction (HS‐SPME) method for the determination of methoxypyrazines in wine. Analysis was performed by using comprehensive two‐dimensional gas chromatography with novel detection capabilities, including nitrogen phosphorus detection (GC×GC‐NPD) and time‐of‐flight mass spectrometry (GC×GC‐TOFMS). In the latter, stable isotope dilution was performed for the quantitation of 2‐methoxy‐3‐(2‐methylpropyl) pyrazine (IBMP), using labelled 2‐( 2 H 3 )methoxy‐3‐(2‐methylpropyl)pyrazine ( d 3 ‐IBMP) as the internal standard, and resolution of the two analogues was facilitated using the deconvolution capabilities of the TOFMS. This research represents the first report of HS‐SPME with isotope dilution and GC×GC‐TOFMS (GC×GC‐IDTOFMS). Analysis by GC×GC‐NPD enabled detection limits of 0.5 ng/L for the quantitation of IBMP, which was superior to that obtained using GC×GC‐IDTOFMS (1.95 ng/L). Nevertheless, both methods were adequately sensitive for real wine analysis, yielding highly comparable IBMP concentrations of 26.1 and 27.8 ng/L, respectively, from a Sauvignon blanc wine. The complexity of the real wine headspace was simplified as a result of selective detection using GC×GC‐NPD and, in the case of GC×GC‐IDTOFMS, the use of extracted ion chromatograms (EICs).
Headspace solid-phase microextraction combined with GC× GC-TOFMS for the analysis of volatile compounds of Coptis species rhizomes
Publisher: Wiley
Date: 13-04-2200
Abstract: In this study, the investigation of the volatile compounds of dried rhizomes of Coptis chinensis Franch, C. deltoidea C. Y. Cheng et Hsiao, and C. teeta Wall was carried out to complete the chemical composition of these valuable natural products. Volatile profiles were established and compared after headspace solid-phase microextraction (HS-SPME) using a polydimethylsiloxane/ inylbenzene (PDMS/DVB, 65 μm) fibre coupled to comprehensive 2D gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS). Analyses were performed and compared on two column-phase combinations (non-polar olar and polar/non-polar). The majority of the identified compounds eluted as well-separated (pure) components as a result of high-resolution capability of the GC×GC method, which significantly reduces co-elution. Therefore, this increases the likelihood that pure mass spectra can be obtained. More than 290 volatile and semi-volatile organic compounds were tentatively characterized by means of GC×GC in tandem with TOFMS detection. Improved result interpretations were obtained in terms of compound classification based on the organized structure of the peaks of structurally related compounds in the GC×GC contour plot. These compounds are distributed over the chemical groups of hydrocarbons, acids, alkenes, alkynes, aldehydes, ketones, alcohols, esters, furans, and terpenoids. Among all the chemical groups, terpenoids present the higher number of identified compounds (44), alkenes (41), and aldehydes and ketones (28). This study completed the volatile phytochemical analysis of the headspace composition of various Coptis species rhizomes, and should serve as a means to identify the difference between the rhizomes and may also be useful to confirm in idual species based on their volatile chemical profile.
Simulation of peak position and response profiles in comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 12-2019
DOI: 10.1016/J.CHROMA.2019.460392
Abstract: Approaches to simulate peak time and intensity profiles of compounds in comprehensive two dimensional gas chromatography (GC × GC) were developed, and which are demonstrated for separation of a mixture of saturated and unsaturated fatty acid methyl esters (FAME) using a range of column sets. The simulation of first and second dimension time (
Oxidised compounds in aviation fuels using Nafion fibre solid phase microextraction
Publisher: Elsevier BV
Date: 06-2017
Erratum:From Molecular Structures of Ionic Liquids to Predicted Retention of Fatty Acid Methyl Esters in Comprehensive Two-Dimensional Gas Chromatography Gas Chromatography(ChemPlusChem(2014)6(790-797)10.1002/cplu.201300410)
Publisher: Wiley
Date: 11-2014
Quantitative preparative gas chromatography of caffeine with nuclear magnetic resonance spectroscopy
Publisher: Wiley
Date: 27-04-2013
Abstract: Caffeine test solute was employed in combination with an internal standard (IS), 1,4-dimethoxybenzene, in preparative-gas chromatography (prep-GC), with nuclear magnetic resonance (NMR) experiments. The IS served to: (i) quantify the trapping efficiency of an external trapping assembly, consisting of a capillary column cryotrap at the end of the analytical column (ii) quantify the solute response in different NMR s les and (iii) permit correlation of expected level of response of a compound in the NMR experiment, based on relative responses of the IS and solute in the GC result. The recovery rate of caffeine from multiple injections of s le (1×, 2×, 5× and 10×) was 69.6 ± 1.3%, which correlated well (R(2) = 0.999) with the number of injections of compound. The (1)H-NMR spectrum was sufficient to enable structural characterisation of the reference caffeine compound, and was achieved with recovery of amounts of ≤10 μg from a single aliquot. Less than 400 μg of collected caffeine (40 replicate injections) was sufficient for structural characterisation by (13)C-NMR spectral analysis. The method allows development of approaches to separate unknown compounds in complex s les, and to separately use MS and NMR for their characterisation.
Orthogonality considerations in comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 04-2005
DOI: 10.1016/J.CHROMA.2004.09.020
Abstract: This study explores separation orthogonality with respect to comprehensive two-dimensional gas chromatography (GC x GC) for a range of different column polarities in the first dimension (1D), with two second dimension (2D) column types. Systematic variation in the net polarity of the first dimension allows the effect of column phase relative polarity on analyte retention in both the first and second dimensions to be evaluated. First dimension polarity manipulation significantly affects elution temperature (T(e)) of the analytes. This alters the magnitude of retention on the second dimension, and the extent of utility of separation space. By use of retention factor/temperature data in single column experiments, along with 1D T(e) data, retention on the 2D column can be estimated. This allows the two-dimensional separation to be predicted, and compared with experimental data. Predicted GC x GC peak positions corresponded favourably with the experimentally derived chromatograms, yielding a simple approach for predicting two-dimensional separations, using unique column set combinations.
Identification of potent odourants in wine and brewed coffee using gas chromatography-olfactometry and comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 10-2011
DOI: 10.1016/J.CHROMA.2011.06.039
Abstract: Volatile constituents in wine and brewed coffee were analyzed using a combined system incorporating both GC-olfactometry (GC-O) and comprehensive two-dimensional GC-flame ionization detection (GC×GC-FID). A column set consisting of a 15m first dimension ((1)D DB-FFAP (free fatty acid phase)), and a 1.0m (2)D column (DB-5 phase) was applied to achieve the GC×GC separation of the volatile extracts isolated by using solid phase extraction (SPE). While 1D GC resulted in many overlapping peaks, GC×GC allowed resolution of co-eluting compounds which coincided with the odour region located using GC-O. Character-impact odourants were tentatively identified through data correlation of GC×GC contour plots across results obtained using either time-of-flight mass spectrometry (TOFMS), or with flame photometric detection (FPD) for sulfur speciation. The odourants 2-methyl-2-butenal, 2-(methoxymethyl)-furan, dimethyl trisulfide, 2-ethyl-5-methyl-pyrazine, 2-octenal, 2-furancarboxaldehyde, 3-mercapto-3-methyl-1-butanol, 2-methoxy-3-(2-methylpropyl)-pyrazine, 2-furanmethanol and isovaleric acid were suspected to be particularly responsible for coffee aroma using this approach. The presented methodology was applied to identify the potent odourants in two different Australian wine varietals. 1-Octen-3-ol, butanoic acid and 2-methylbutanoic acid were detected in both Merlot and a Sauvignon Blanc+Semillon (SV) blend with high aroma potency. Several co-eluting peaks of ethyl 4-oxo-pentanoate, 3,7-dimethyl-1,5,7-octatrien-3-ol, (Z)-2-octen-1-ol, 5-hydroxy-2-methyl-1,3-dioxane were likely contributors to the Merlot wine aroma while (Z)-3-hexen-1-ol, β-phenylethyl acetate, hexanoic acid and co-eluting peaks of 3-ethoxy-1-propanol and hexyl formate may contribute to SV wine aroma character. The volatile sulfur compound 2-mercapto-ethyl acetate was believed to contribute a fruity, brothy, meaty, sulfur odour to Australian Merlot and SV wines.
Electrospray mass spectrometry of zinc dithiophosphate derivatives and its application to the analysis of engine oil antiwear additives
Publisher: Elsevier BV
Date: 08-1993
Investigation of folic acid stability in fortified instant Asian noodles by use of capillary electrophoresis
Publisher: Elsevier BV
Date: 2009
Liquid chromatography – quadrupole Orbitrap mass spectrometry method for selected pharmaceuticals in water samples
Publisher: Elsevier BV
Date: 09-2017
DOI: 10.1016/J.CHROMA.2017.08.003
Abstract: This study developed an analytical approach for sub-ppb level detection and confirmation of 13 pharmaceuticals and personal care products (PPCPs) in water s les using ultra high pressure liquid chromatography hyphenated with a quadrupole Orbitrap mass spectrometer (UHPLC- Q-Orbitrap-MS). S le preparation was performed by using solid phase extraction (SPE) employing hydrophilic-lipophilic balance cartridges, with elution of sorbed analytes using methanol. Acceptable automatic gain control (AGC) target and maximum injection time (IT) were 1×10
Solid-phase micro-extraction - Comprehensive two-dimensional gas chromatography of ginger (Zingiber officinale) volatiles
Publisher: Wiley
Date: 16-12-2003
DOI: 10.1002/FFJ.1133
Effects of temperature and flow regulated carbon dioxide cooling in longitudinally modulated cryogenic systems for comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 07-2002
DOI: 10.1016/S0021-9673(02)00433-8
Abstract: Two different modes of temperature regulation in longitudinally modulated cryogenic systems (LMCSs) for comprehensive two-dimensional gas chromatography (GC x GC) were compared. Carbon dioxide was used as coolant. In the first mode of operation, the temperature of the trap was regulated to pre-set temperature using a digital temperature controller ("the constant temperature mode"). In the second, the temperature was regulated to a fixed negative offset to the oven temperature by using a constant flow of CO2 ("the constant flow mode"). A number of problems were occasionally observed using the constant temperature mode: (1) severe band broadening of high boiling analytes in the second dimension (2) non-Gaussian reconstructed first-dimension peak profiles (3) high background due to modulation of first-dimension column bleed. It was concluded that these problems were associated with inefficient solute remobilization at low LMCS trap temperatures (1 and 2) or large trap temperature fluctuations (3). These problems could be avoided or significantly reduced by using the constant flow mode. Best results were obtained as the trap temperature was kept about 70 degrees C below the oven temperature.
Introducing Students to Gas Chromatography-Mass Spectrometry Analysis and Determination of Kerosene Components in a Complex Mixture
Publisher: American Chemical Society (ACS)
Date: 22-01-2016
Evaluation of World Anti-Doping Agency criteria for anabolic agent analysis by using comprehensive two-dimensional gas chromatography-mass spectrometry
Publisher: Springer Science and Business Media LLC
Date: 21-01-2010
DOI: 10.1007/S00216-009-3415-3
Abstract: This work presents the validation study of the comprehensive two-dimensional gas chromatography (GC x GC)-time-of-flight mass spectrometry method performance in the analysis of the key World Anti-Doping Agency (WADA) anabolic agents in doping control. The relative abundance ratio, retention time, identification and other method performance criteria have been tested in the GC x GC format to confirm that they comply with those set by WADA. Furthermore, tens of other components were identified with an average similarity of >920 (on the 0-999 scale), including 10 other endogenous sterols, and full mass spectra of 5,000+ compounds were retained. The testosterone/epitestosterone ratio was obtained from the same run. A new dimension in doping analysis has been implemented by addressing separation improvement. Instead of increasing the method sensitivity, which is accompanied by making the detector increasingly "blind" to the matrix (as represented by selected ion monitoring mode, high-resolution mass spectrometry (MS) and tandem MS), the method capabilities have been improved by adding a new "separation" dimension while retaining full mass spectral scan information. Apart from the requirement for the mass spectral domain that a minimum of three diagnostic ions with relative abundance of 5% or higher in the MS spectra, all other WADA criteria are satisfied by GC x GC operation. The minimum of three diagnostic ions arises from the need to add some degree of specificity to the acquired mass spectrometry data however, under the proposed full MS scan method, the high MS similarity to the reference compounds offers more than the required three diagnostic ions for an unambiguous identification. This should be viewed as an extension of the present criteria to a full-scan MS method.
Multidimensional gas chromatographic‒Mass spectrometric method for separation and identification of triacylglycerols in olive oil
Publisher: Elsevier BV
Date: 10-2020
Preparative Gas Chromatography
Publisher: Elsevier
Date: 2012
Study of the enantioseparation of imazaquin and enantioselective degradation in field soils by CZE
Publisher: Wiley
Date: 26-07-2007
Abstract: A fast, simple, and sensitive CE method was developed to study the separation and degradation of imazaquin enantiomers in field soils. The parameters pH and concentration of the buffer electrolyte, type and concentration of the chiral selectors, applied voltage, and temperature of the CE system were investigated. Sodium hydrogen phosphate (50 mM) at pH 10.1 containing 30 mM hydroxypropyl-beta-CD (HP-beta-CD) was found to be the suitable BGE. The reliable determination for imazaquin enantiomers was obtained at 20 kV applied voltage, 15 degrees C separation system, and detection at 214 nm. Under the optimal conditions, the LODs (S/N = 3) were 0.0097 and 0.0098 mg/kg linearity ranged from 0.019 to 1.24 and 0.020 to 1.26 mg/kg for the first-eluting peak of imazaquin (imazaquin-I) and the second-eluting peak of imazaquin (imazaquin-II) in soil, respectively. The precision in terms of the percentage of RSD (%RSD) calculated from peak area was not greater than 5%. With the suitable characteristics of the present method, it was applied to the study of enantioselective degradation in field soil. According to the calculated values of the enantiomer ratio (ER) and the rate constant of degradation (k), the results suggested that the degradation rate of the two enantiomers were slightly different, and that the pH of the soil had a strong influence on the rate of degradation.
Rapid sequential separation of essential oil compounds using continuous heart-cut multi-dimensional gas chromatography-mass spectrometry
Publisher: Elsevier BV
Date: 05-2011
DOI: 10.1016/J.CHROMA.2011.02.060
Abstract: A method for separation and identification of peaks in essential oil s les based on rapid repetitive heart-cutting using multidimensional gas chromatography (MDGC)-mass spectrometry (MS) coupled with a cryotrapping interface is described. Lavender essential oil is analyzed by employing repetitive heart-cut intervals of 1.00 and 1.50 min, achieved in a parallel MDGC-MS/GC-FID experiment. The number of peaks that were detected in 1D GC operation above a given response threshold more than tripled when MDGC-MS employing the cryotrapping module method was used. In addition, MDGC-MS enabled detection of peaks that were not in idually evident in 1D GC-MS, owing to effective deconvolution in time of previously overlapped peaks in 1D GC. Thus separation using the cryomodulation approach, without recourse to using deconvolution software, was possible. Peaks widths decreased by about 5-7-fold with the described method, peak capacity increased from about 9 per min to 60 per min, and greater sensitivity results. Repeatability of retention times for replicate analyses in the multidimensional mode was better than 0.02% RSD. The present study suggests that the described heart-cutting technique using MDGC-MS can be used for general improvement in separation and identification of volatile compounds.
Application of comprehensive two-dimensional gas chromatography to sterols analysis
Publisher: Elsevier BV
Date: 12-2008
DOI: 10.1016/J.CHROMA.2008.10.045
Abstract: The applicability of comprehensive two-dimensional gas chromatography (GCxGC) for sterol analysis was investigated by separation and identification of endogenous sterols in standards, and spiked in human urine. The modulation temperature was optimized to achieve the best separation and signal enhancement. The separation pattern of trimethylsilyl (TMS) derivatives of sterols was compared on two complementary column sets. Whilst the BPX5/BPX50 column set offers better overall separation, BPX50/BPX5 provides better peak shape and sensitivity. Comparison of the identification power of GCxGC-TOFMS against both the NIST05 MS library and a laboratory created (in-house) TOFMS library was carried out on a free sterols extract of urine, derivatised and spiked at the World Anti-Doping Agency (WADA) limit of 2 ng mL(-1). The average match quality for 19 analysed sterols on the BPX50/BPX5 column set was 950/1000 when searched against the in-house library only four were identified against the NIST05 library, at a match threshold of 800. The match quality of GCxGC-TOFMS spectra was superior to that for analysis using 1D GC-TOFMS for sterols spiked in urine at 10 ng mL(-1). An r(2)>0.997 was obtained for the concentration range between 0.25 ng mL(-1) and 10 ng mL(-1) for three selected sterols. The lowest limit of detection (LOD) was obtained for estrone (0.1 ng mL(-1)) and the highest LOD was for 5alpha-androstan-3alpha,11beta-diol-17-one, epitestosterone and cholesteryl butyrate (1 ng mL(-1)), using a match threshold of at least 800 and signal-to-noise ratio of at least 10. TOFMS coupled to GCxGC enabled satisfactory identification of sterols in urine at their LOD. A minimum acceptable match (MAM) criterion for urinary sterols using 2D retention times and TOF mass spectra is introduced. This study shows that GCxGC-TOFMS yields high specificity for steroids derived from urine, with detection limits appropriate for use in doping control.
Direct Analysis of Synthetic Phenolic Antioxidants, and Fatty Acid Methyl Ester Stability in Biodiesel by Liquid Chromatography and High-Resolution Mass Spectrometry
Publisher: Springer Science and Business Media LLC
Date: 18-12-2019
Chemometrics in comprehensive multidimensional separations
Publisher: Springer Science and Business Media LLC
Date: 10-06-2011
DOI: 10.1007/S00216-011-5139-4
Abstract: Chemometric methods have critical importance for the discovery of the information/knowledge buried or concealed in high-dimensional datasets acquired from comprehensive multidimensional separations (CMDS), and for interpretation of experiments or chemical processes. In this work, employment of new developments in chemometrics making full use of the data to maximize the potential of CMDS to resolve mathematically a variety of practical problems is reviewed whilst providing the authors' point of view. During the past several years, chemometrics has been successfully applied to many areas of concern to CMDS investigation, including experimental parameter optimization, data quality improvement, identification and quantification of target chemical components, pattern recognition technique for clustering and classification, multivariate model establishment to correlate chromatographic properties and molecular descriptors. On the basis of the high-dimensionality characteristics of CMDS, some special aspects such as evaluation of orthogonality and image processing have also been included in this review. It is expected that an overview of the erse ways in which chemometrics can aid CMDS investigations will prove valuable to interested users in this area through a comprehensive survey of previous research contributions. Chemometrics lends itself well to the powerful separation capability of CMDS.
Application of integrated comprehensive/multidimensional gas chromatography with mass spectrometry and olfactometry for aroma analysis in wine and coffee
Publisher: Elsevier BV
Date: 10-2015
DOI: 10.1016/J.FOODCHEM.2015.04.003
Abstract: Component coelution in chromatographic analysis complicates identification and attribution of in idual odour-active volatile molecules in complex multi-component s les. An integrated system incorporating comprehensive two-dimensional gas chromatography (GC × GC) and multidimensional gas chromatography (MDGC), with flame ionisation, olfactometry and mass spectrometry detection was developed to circumvent data correlation across different systems. Identification of potent odorants in Shiraz wine and the headspace of ground coffee are demonstrated as selected applications. Multiple solid-phase microextraction (SPME) s ling with GC-O located odour-active regions GC × GC established the complexity of odour-active regions MDGC provided high-resolution separation for each region simultaneous 'O' and MS detection completed the analysis for target resolved peaks. Seven odour regions in Shiraz were analysed with MDGC-O/MS detection, revealing 11 odour volatiles through matching of mass spectrometry and retention indices from both separating dimensions, including acetic acid octen-3-ol ethyl octanoate methyl-2-oxo-nonanoate butanoic acid, 2-methylbutanoic acid, and 3-methylbutanoic acid 3-(methylthio)-1-propanol hexanoic acid β-damascenone and ethyl-3-phenylpropanoate. A capsicum odour in ground coffee was identified as 2-methoxy-3-isobutylpyrazine with a 5-fold increase in S/N of the odorant when acquired using a 6-time cumulative SPME s ling approach.
Metal–organic frameworks as stationary phases for mixed-mode separation applications
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4CC00933A
Abstract: Polymorphic metal-organic framework (MOF) materials offer a platform for small-scale separation of complex mixtures of polycyclic aromatic hydrocarbons (PAHs) and polar compounds. Retention factors show dependence on both analyte dimensions and polarity, suggesting mixed-mode separation, allowing complete resolution of some analytes from multi-component mixtures.
Nomenclature for Comprehensive Multidimensional Chromatography in Portuguese language,Nomenclatura na língua Portuguesa em cromatografia multidimensional abrangente
Publisher: FapUNIFESP (SciELO)
Date: 06-2007
Switchable Enantioselective Three- and Four-Dimensional Dynamic Gas Chromatography–Mass Spectrometry: Example Study of On-Column Molecular Interconversion
Publisher: American Chemical Society (ACS)
Date: 02-05-2017
DOI: 10.1021/ACS.ANALCHEM.7B00853
Abstract: A novel hybrid online enantioselective four-dimensional dynamic GC (e4D-DGC) approach to study reversible molecular interconversion through specific isolation of a diastereo and enantiopure oxime, 2-phenylpropanaldehyde oxime, from prior multidimensional separation, is described. It incorporates a pre-enantioseparation step that applies comprehensive two-dimensional GC (GC × GC), prior to multiple microfluidic (Deans) switching for selection of components of a diastereomeric (E,Z) and enantiomeric (R,S) oxime into a third reactor column where isomerization occurs. This is followed by E/Z separation in a fourth analytical column. The enantioselective first dimension (
New approaches to monitor semi-volatile organic compounds released during coffee roasting using flow-through/active sampling and comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 05-2019
DOI: 10.1016/J.FOODRES.2019.02.009
Abstract: A novel dynamic approach is described to profile volatile organic compound (VOC) and semi-VOC (SVOC) emission during coffee roasting aimed at analysing components present in the roasting plume, and to monitor their evolution during the process. Two sorbents - coconut shell charcoal (CSC) and styrene- inylbenzene resin (XAD-2) - were evaluated while collecting substances in four sequential time intervals (0-3, 3-6, 6-9 and 9-12 min). Extracted VOCs ( 400 Da. GC × GC resolved many co-eluting compounds observed in 1D GC and allowed chemical group type cluster analysis, revealing that many non-polar VOCs are observed within the 0-3 min interval, and that the release of polar and higher molar mass SVOCs were mostly found within the 3-6 min interval. These group-type cluster analyses offer a broad spectrum chemical profile of the released substances. It may also reveal detailed insights into the roast process evolution over time.
Headspace solid-phase microextraction - Comprehensive two-dimensional gas chromatography of wound induced plant volatile organic compound emissions
Publisher: Royal Society of Chemistry (RSC)
Date: 2002
DOI: 10.1039/B208577A
Abstract: Plant emissions of volatile organic compounds from mechanically wounded Agrostis stolonifera, Pennisetum clandestinum, Eucalyptus leucoxylon and Trifolium repens have been s led by headspace-solid phase microextraction (HS-SPME) and analysed by using comprehensive two-dimensional gas chromatography (GCxGC) for measurement of the plant emissions. GCxGC produces a fingerprint of the volatile organic compounds in a 2D separation space that may be approximately interpreted as a boiling point-polarity space, and may then be presented as a two-dimensional contour plot. This allows identification of s le-dependent variations in component distributions in the 2D plot, which will contain information about plant differences and should therefore facilitate recognition of different plant materials and displays the gross differences in volatiles between each plant species.
Rapid Plant Volatiles Screening Using Headspace SPME and Person-Portable Gas Chromatography–Mass Spectrometry
Publisher: Springer Science and Business Media LLC
Date: 06-09-2019
Photocatalytic Degradation of Secondary Alcohol Ethoxylate: Spectroscopic, Chromatographic, and Mass Spectrometry Studies
Publisher: American Chemical Society (ACS)
Date: 09-1901
DOI: 10.1021/ES00009A013
From molecular structures of ionic liquids to predicted retention of fatty acid methyl esters in comprehensive two-dimensional gas chromatography
Publisher: Wiley
Date: 11-04-2014
Analysis of strawberry volatiles using comprehensive two-dimensional gas chromatography with headspace solid-phase microextraction
Publisher: Elsevier BV
Date: 05-03-2005
DOI: 10.1016/J.JCHROMB.2004.05.021
Abstract: The aims of the current study were to develop an enantioselective multi-dimensional gas chromatography (GC x GC) method for the examination of strawberry volatiles and to use this method to make comparisons between the volatile profiles of different cultivars and between fresh picked and post-harvest berries of the same cultivar. Strawberry volatiles were s led using solid-phase microextraction (SPME), and the repeatability and reproducibility of this method was examined. Semi-quantitative analysis of the volatiles was conducted using the relatively new technique of comprehensive multi-dimensional gas chromatography, using enantioselective (chiral) columns for the differentiation of analyte enantiomers. Chiral GC x GC facilitated the detection of key enantiomers in strawberry flavour. The (-)-enantiomer of 2,5-dimethyl-4-hydroxy-(2H)-furan-3-one (DMHF) and the S-enantiomer of linalool were tentatively identified as the predominant forms in both the cultivars Selva and Adina. The compounds benzaldehyde and methyl hexanoate were shown to decrease in post-harvest berries, whilst DMHF and nerolidol increased upon storage.
Characterisation of lavender essential oils by using gas chromatography-mass spectrometry with correlation of linear retention indices and comparison with comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 09-2012
DOI: 10.1016/S0021-9673(02)00653-2
Abstract: Nine s les of lavender essential oil were analysed by GC-MS using low-polarity and polar capillary columns. Linear retention indices (LRI) were calculated for each component detected. Characterisation of the in idual components making up the oils was performed with the use of an mass spectrometry (MS) library developed in-house. The MS library was designed to incorporate the chromatographic data in the form of linear retention indices. The MS search routine used linear retention indices as a post-search filter and identification of the "unknowns" was made more reliable as this approach provided two independent parameters on which the identification was based. Around 70% of the total number of components in each s le were reliably characterised. A total of 85 components were identified. Semi-quantitative analysis of the same nine s les was performed by gas chromatography (GC) with flame ionisation detection (FID). The identified components accounted for more than 95% of each oil. By comparing the GC-MS results with the results from the GCxGC-FID analysis of a lavender essential oil, many more components could be found within the two-dimensional separation space.
Qualitative analysis of Copaifera oleoresin using comprehensive two-dimensional gas chromatography and gas chromatography with classical and cold electron ionisation mass spectrometry
Publisher: Elsevier BV
Date: 12-2016
DOI: 10.1016/J.CHROMA.2016.11.038
Abstract: Improved separation of both sesquiterpenes and diterpenic acids in Copaifera multijuga Hayne oleoresin, is demonstrated by using comprehensive two-dimensional gas chromatography (GC×GC) coupled to accurate mass time-of-flight mass spectrometry (accTOFMS). GC×GC separation employs polar phases (including ionic liquid phases) as the first dimension (
Comprehensive two-dimensional gas chromatography with fast enantioseparation
Publisher: American Chemical Society (ACS)
Date: 17-09-2002
DOI: 10.1021/AC025803E
Abstract: The development of fast chiral analysis for use in comprehensive two-dimensional gas chromatography in which a short second dimension enantioselective capillary column provides a route to precise measurement of chiral ratios of enantiomers is described. Retention times as short as 8 s are reported for (+/-)-limonene, with adequate enantioseparation maintained (Rs approximately 1.0) on a 1-m cyclodextrin derivative-coated capillary column. Sufficiently fast elution on the second column was achieved by using GC/ MS in which the subambient pressure (vacuum outlet) conditions promote increased diffusion coefficients and higher component volatility a 4-fold reduction of second-dimension retention time was observed, as compared with ambient pressure outlet conditions. The enantiomeric distribution of several monoterpene compounds in bergamot essential oil is reported as a demonstration of the method. Total analysis time of the target components was approximately 8.5 min.
Comprehensive two-dimensional gas chromatography improves separation and identification of anabolic agents in doping control
Publisher: Elsevier BV
Date: 4220
DOI: 10.1016/J.CHROMA.2009.10.075
Abstract: The application of comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GCxGC-TOFMS) for the analysis of six anabolic agents (AAs) in doping control is investigated in this work. A non-polar-polar column configuration with 0.2microm film thickness (d(f)) second dimension ((2)D) column was employed, offering much better spread of the components on (2)D when compared to the alternative 0.1microm d(f)(2)D column. The proposed method was tested on the "key" AA that the World Anti-Doping Agency (WADA) had listed at the low ngmL(-1) levels (clenbuterol, 19-norandrosterone, epimethendiol, 17alpha-methyl-5alpha-androstane-3alpha,17beta-diol, 17alpha-methyl-5beta-androstane-3alpha,17beta-diol and 3'-OH-stanozolol). The compounds were spiked in a blank urine extract obtained by solid-phase extraction, hydrolysis and liquid-liquid extraction prior to analysis they were converted to the corresponding trimethylsilyl (TMS) derivatives. The limit of detection (LOD) was below or equal to the minimum required performance limit (MRPL) of 2ngmL(-1) defined by WADA, and the correlation coefficient was in the range from 0.995 to 0.999. The method allows choosing an ion from the full mass spectra which shows the least interference from the matrix and/or the best sensitivity this can only be done if full scan mass spectral data are available. The advantage of GCxGC over classical one-dimensional GC (1D GC), in terms of separation efficiency and sensitivity, is demonstrated on a positive urine control s le at a concentration of 5ngmL(-1). The obtained similarity to the in-house created TOFMS spectra library at this level of concentration was in the range from 822 to 932 (on the scale from 0 to 999). Since full mass spectral information are recorded, the method allows the retro-search of non-target compounds or new "designer steroids", which cannot be detected with established GC-MS methods that use selected ion monitoring (SIM) mode.
Thermally sensitive behavior explanation for unusual orthogonality observed in comprehensive two-dimensional gas chromatography comprising a single ionic liquid stationary phase
Publisher: American Chemical Society (ACS)
Date: 17-12-2015
DOI: 10.1021/AC5030039
Abstract: In this study, a theoretical concept and method to achieve a degree of orthogonality in comprehensive two-dimensional gas chromatography (GC × GC) for separation of fatty acid methyl esters (FAME) by using a single ionic liquid (IL) stationary phase (1-phase-GC × GC) were established. The 1-phase system comprises a long IL column and shorter IL column of the same phase before and after the modulation region, operated under temperature-programmed conditions. Initial isothermal experiments employing six commercial IL columns were conducted at different temperatures. On the basis of the temperature-dependent linear solvation energy relationship (LSER) concept, SLB-IL111 exhibited the greatest thermal sensitivity and degree of difference over the tested temperature (T) range, so it was selected for investigation of the 1-phase-GC × GC mode. With the same temperature program, a significantly high degree of orthogonality was observed for the experiment, varied with column lengths. The switchable separation result, which inverts the retention of saturated and unsaturated FAME on the downstream column ((2)D), was achieved by varying column diameters and surface thicknesses of the IL-coated layers. These results were explained according to the corresponding LSER principles. Also, the time summation model was applied for the simulation of the observed 1-phase-GC × GC results.
Targeted Multidimensional Gas Chromatography Using Microswitching and Cryogenic Modulation
Publisher: American Chemical Society (ACS)
Date: 04-09-2003
DOI: 10.1021/AC034492K
Abstract: A new method is described that allows fast target analysis in multidimensional gas chromatography by using a microswitching valve between two GC columns, with cryogenic trapping and rapid re-injection of trapped solutes in the second dimension. The essence of the procedure is that heart-cut fractions from the first column (1D) can be selectively transferred to column 2 (2D), where a moveable cryogenic trap first focuses the transferred solute(s) at the head of the second column and then permits their facile rapid analysis on 2D. Since 2D is a short narrow-bore column, which exhibits very fast analysis (on the order of a few seconds elution), peak responses (heights) are significantly enhanced (by up to 40-fold). Additionally, by using a 2D phase of a selectivity different from that used for 1D, it is possible to also separate components that are not resolved on the first column and to increase the resolution for other compounds. The heart-cut valve isolates the section(s) of solutes of interest from the first column separation, and this provides a considerable simplification to the chromatogram-in addition to the separation and sensitivity advantages. By using this method, multidimensional gas chromatography with multiple heart-cuts can be completed within the same time as the primary column separation. Since the described method permits non-heart-cut fractions to be transferred to a monitor detector, normal detection of these fractions is still permitted. By modulation of the cryotrap, it is also possible to achieve comprehensive two-dimensional gas chromatography for the heart-cut fractions however, only those compounds passed to the second, separation column, which passes through the cryotrap, will be subjected to GC x GC analysis. The technique and the various modes of operation are described in this paper.
Ultra-fast essential oil characterization by capillary GC on 50 μm ID column
Publisher: Wiley
Date: 06-2004
Abstract: A 5 m x 50 microm capillary column with 0.05 microm stationary phase film thickness, with a calculated efficiency of almost 20,000 plates per metre (under optimum conditions), was used for very fasthigh resolution GC analysis of lime essential oil. The total analysis time of this volatile essential oil was less than 90 s. Fast GC is shown to be appropriate for essential oil quality assurance analysis, and quantitative results of key components are comparable with those obtained by using conventional GC analysis. The fast GC analysis is approximately 33 times faster than the conventional GC method.
Use of comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry for the characterization of biodegradation and unresolved complex mixtures in petroleum
Publisher: Elsevier BV
Date: 11-2010
Component correlation between related samples by using comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry with chemometric tools
Publisher: Elsevier BV
Date: 09-2012
DOI: 10.1016/J.CHROMA.2012.07.032
Abstract: A chemometric strategy has been developed to discover component difference and similarity between two chromatograms (correlation) by using comprehensive two-dimensional (2D) gas chromatography with time-of-flight mass spectrometry (GC×GC-TOFMS). It allows for rapid determination of the presence or absence of analytes of interest in both pure and overlapping peak clusters, and then locates elution windows of target components. First, representative elution windows of analytes are extracted from the 2D GC×GC map to characterize the spectral space and further construct an orthogonal projection matrix for analysis. Next, multi-component spectral correlative chromatography (MSCC) is employed to scan the whole or pre-selected GC×GC-TOFMS data range to obtain component features. An auto-correlative projection curve is proposed to assess the projection residual from MSCC by defining a new evaluation index as reference, based on fixed-size moving window evolving factor analysis. In principle, the method can also be utilized to locate specific compounds whose known spectra are available. It is not restricted by data with high homoscedastic and heteroscedastic noise. Simulated GC-MS data and an extremely complicated herbal product mixture comprising 9 herbs demonstrates that the two-dimensional correlative distribution graph is effective for chemical interpretation between GC×GC-TOFMS data. It allows discovery of information buried in this type of highly complex dataset, especially for rapid and effective data comparison, where specific molecular identity might otherwise be hidden.
Sorption of volatile organics from water using an open-tubular, wall-coated capillary column
Publisher: Royal Society of Chemistry (RSC)
Date: 2000
DOI: 10.1039/A907348E
A review of basic concepts in comprehensive two-dimensional gas chromatography
Publisher: Oxford University Press (OUP)
Date: 05-2002
DOI: 10.1093/CHROMSCI/40.5.276
Abstract: The technique of comprehensive two-dimensional gas chromatography (GCxGC) is reviewed. A description of technical aspects of the method illustrates how the GCxGC result is achieved through the use of dual-coupled columns and the modulation of capillary chromatographic peaks. This review presents an expanded section dealing with the relationship between the modulation phase and frequency and the resulting peak pulse profiles. Experimental results that support the appreciation and understanding of the effects that pulsing has on a chromatographic peak are provided. The main goals of GCxGC analysis are discussed with respect to analytical sensitivity and peak capacity arising from zone compression effects and fast analysis on the second column. A typical application of GCxGC is presented, along with a consideration of implementation of the GCxGC method.
Temperature profiles and heat dissipation in capillary electrophoresis
Publisher: American Chemical Society (ACS)
Date: 24-02-2006
DOI: 10.1021/AC052075X
Abstract: While temperature control is usually employed in capillary electrophoresis (CE) to aid heat dissipation and provide acceptable precision, internal electrolyte temperatures are almost never measured. In principle, this limits the accuracy, repeatability, and method robustness. This work presents a fundamental study that combines the development of new equations characterizing temperature profiles in CE with a new method of temperature determination. New equations were derived from first principles relating the mean, axial, and inner wall electrolyte temperatures (T(Mean), T(Axis), T(Wall)). T(Mean) was shown to occur at a distance 1/ radical3 times the internal radius of the capillary from the center of the capillary and to be a weighted average of (2/3)T(Axis) and (1/3)T(Wall). Conductance (G) and electroosmotic mobility (mu(EOF)) can be used to determine T(Mean) and T(Wall), respectively. Extrapolation of curves of mu(EOF) versus power per unit length (P/L) at different temperatures was used to calibrate the variation of mu(EOF) with temperature (T), free from Joule heating effects. mu(EOF) increased at 2.22%/ degrees C. The experimentally determined temperatures using mu(EOF) agreed to within 0.2 degrees C with those determined using G. The accuracy of G measurements was confirmed independently by measuring the electrical conductivity (kappa) of the bulk electrolyte over a range of temperatures and by calculating the variation of G with T from the Debye-Hückel-Onsager equation. T(Mean) was found to be up to 20 degrees C higher than the external temperature under typical conditions using active air-cooling and a 74.0-microm-internal diameter (di) fused-silica capillary. A combination of experimentally determined and calculated temperatures enables a complete temperature profile for a fused-silica capillary to be drawn and the thickness of the stationary air layer to be determined. As an ex le, at P/L = 1.00 Wm(-1), the determined radial temperature difference across the electrolyte was 0.14 degrees C the temperature difference across the fused-silica wall was 0.17 degrees C, across the poly(imide) coating was 0.13 degrees C, and across the stationary air layer was 2.33 degrees C.
Foods and Contaminants Analysis Using Multidimensional Gas Chromatography: An Update of Recent Studies, Technology, and Applications
Publisher: American Chemical Society (ACS)
Date: 10-01-2023
Capillary GC and GC-MS of porphyrins and metalloporphyrins
Publisher: Springer Science and Business Media LLC
Date: 12-1982
DOI: 10.1007/BF02258926
Evaluation of comprehensive two-dimensional gas chromatography with flame photometric detection: Potential application for sulfur speciation in shale oil
Publisher: Elsevier BV
Date: 11-2013
DOI: 10.1016/J.ACA.2013.07.021
Abstract: Flame photometric detection in the sulfur channel has been evaluated for sulfur speciation and quantification in comprehensive two-dimensional gas chromatography [GC × GC-FPD(S)] for S-compound speciation in shale extracts. Signal non-linearity and potential quenching effects were reportedly major limitations of this detector for analysis of sulfur in complex matrices. However, reliable linear relationships with correlation coefficient >0.99 can be obtained if the sum of the square root of each modulation slice in GC × GC is plotted vs. sulfur concentration. Furthermore, the quenching effects are reduced due to essentially complete separation of S-containing components from the hydrocarbon matrix. An increase of S/N of up to 150 times has been recorded for benzothiophene and dibenzothiophene in GC × GC-FPD when compared to GC-FPD due to the modulation process. As a consequence, 10 times lower detection limits were observed in the former mode. The applicability of the method was demonstrated using shale oil s le extracts. Three sulfur classes were completely separated and the target class (thiophenes) was successfully quantified after the rest of the s le was erted to the second detector by using a heart-cut strategy. Based on the proposed method, 70% of the sulfur in the shale oil was assigned to the thiophenes, 24% to benzothiophenes, and 5% to dibenzothiophene compounds.
Development and Application of a Novel Multiloop Splitter-Based Non-cryogenic Artificial Trapping Modulation System in Comprehensive Two-Dimensional Gas Chromatography
Publisher: American Chemical Society (ACS)
Date: 08-06-2023
Isomerization Processes Observed for Chromium Compounds by Using the Gas Chromatographic Reactor
Publisher: American Chemical Society (ACS)
Date: 09-1986
DOI: 10.1021/IC00240A032
Assessment of the phytochemical profiles of novel hop (Humulus lupulus L.) cultivars: A potential route to beer crafting
Publisher: Elsevier BV
Date: 03-2019
DOI: 10.1016/J.FOODCHEM.2018.09.082
Abstract: This study investigated the volatile phytochemical ersity of 30 s les obtained from experimental hybrid and commercial H. lupulus L. plants. Essential oils distilled from these s les were analysed by high resolution gas chromatography coupled with accurate mass time-of-flight mass spectrometry (GC-accTOFMS). A total of 58 secondary metabolites, mainly comprising 18 esters, 6 monoterpene hydrocarbons, 2 oxygenated monoterpenes, 20 sesquiterpene hydrocarbons, 7 oxygenated sesquiterpenes, and 4 ketones, were positively or tentatively identified. A total of 24 metabolites were detected in all s les, but commercial cultivars (selected for brewing performance) had fewer compounds identified compared to experimental genotypes. Chemometrics analyses enabled distinct differentiation of experimental hybrids from commercial cultivars, discussed in terms of the different classes of compounds present in different genotypes. Differences among the mono- and sesquiterpenoids, appear to be related to either: i) the genetic origin of the plants or ii) the processes of bioaccumulation of the identified secondary metabolites.
Variation of zeta-potential with temperature in fused-silica capillaries used for capillary electrophoresis
Publisher: Wiley
Date: 02-2006
Abstract: The temperature variation of electroosmotic mobility corrected for the effects of Joule heating (muEOF0) was employed to investigate the variation of the zeta-potential (zeta) with temperature in fused-silica capillaries. Experimentally determined values for zeta increased at 0.39% per degrees C, a rate that is about four to five times smaller than reported previously. Experimentally determined values of zeta were directly proportional to the absolute temperature although values were also influenced slightly by changes to the dielectric constant. It was found that the effective charge density at the inner surface of the capillary was independent of temperature.
Detector technologies for comprehensive two-dimensional gas chromatography
Publisher: Wiley
Date: 08-2006
Abstract: The detector is an integral and important part of any chromatographic system. The chromatographic peak profiles (i.e. peak separation) should, ideally, be unaffected by the detector--it should only provide the sensing capacity required at the end of a column separation process. The relatively new technique of comprehensive 2-D GC (GC x GC) extends the performance of GC manyfold, but comes at a price--existing GC systems may not be adequately designed with the requirements of GC x GC in mind. This is primarily the need for precise measurement of very fast peaks entering the detector (e.g. as fast as 50 ms basewidth in some instances). The capacity of the detector to closely track a rapidly changing chromatographic peak profile depends on a number of factors, such as design of flow paths and make-up gas introduction, type of detector response mechanism, and the chemistry of the response. These factors are discussed here as a means to appreciate the technical demands of detection in GC x GC. The MS detector will not be included in this review.
Modulation ratio in comprehensive two-dimensional gas chromatography
Publisher: American Chemical Society (ACS)
Date: 16-05-2006
DOI: 10.1021/AC052270B
Abstract: Comprehensive two-dimensional chromatography employs a serially coupled two-column arrangement where effluent from the first column is collected or s led and then introduced to the second column according to a chosen modulation period. This is effected by use of a modulator at or near the column junction. One of the considerations in applying the technique is the period of the modulator, which determines the s ling duration of the first column effluent. Here, we propose that the s ling rate can be most effectively described by a new term, called the modulation ratio (MR). This is defined as the ratio of 4 times the first column peak standard deviation (4sigma) ided by the modulation period (PM) or 1.6985 times the half-height width of the peak (wh): MR = 4sigma/PM = wb/PM = (wh x 1.6985)/PM. The 4sigma value is more commonly recognized as the peak base width (wb). The use of 4sigma as the numerator is preferred to simply sigma because when the PM value used for an experiment is equal to sigma, then the MR value is calculated to be 4, implying that the primary peak will be modulated approximately 4 times as is normally recommended for a comprehensive multidimensional separation. The less well-defined term of modulation number (NM) has been previously used and proposed as the number of modulations per peak and, therefore, is intended to convey the manner in which the primary column peak is s led this is a subjective and not well-characterized value. The use of MR should provide users with a meaningful and strictly defined value when reporting experimental conditions. The utility of MR is demonstrated through a mathematical model of the modulation process for both Gaussian and tailing peaks, supported by an experimental study of the modulation ratio. It is shown that for the analysis of trace compounds where precise quantitative measurements are being made, the experiment should be conducted with an MR of at least 3. Conversely, for semiquantitative methods or the analysis of major components, an MR of approximately 1.5 should suffice.
Advanced and innovative chromatographic techniques for the study of citrus essential oils
Publisher: Wiley
Date: 2005
DOI: 10.1002/FFJ.1556
Comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC x GC-TOFMS) for drug screening and confirmation
Publisher: Elsevier BV
Date: 07-2004
Application of microscale-preparative multidimensional gas chromatography with nuclear magnetic resonance spectroscopy for identification of pure methylnaphthalenes from crude oils
Publisher: Elsevier BV
Date: 12-2008
DOI: 10.1016/J.CHROMA.2008.10.102
Abstract: Mass spectrometry is often insufficient to distinguish between structural isomers, requiring confirmation using NMR spectroscopy. Here, a novel preparative technique based upon capillary multidimensional gas chromatography to isolate pure volatile components from complex s les is described. The method was developed through isolation of 1,4-dimethoxybenzene (5.2 microg, 10 injections) from a peppermint essential oil. Then isomers of 1- and 2-methylnaphthalene were isolated from a complex crude oil in sufficient amounts (3.1 microg, 38 injections and 5.0 microg, 35 injections) for discrimination using (1)H NMR spectroscopy. This methodology is applicable to identify any volatile molecule in complex matrices requiring confirmation using NMR spectroscopy.
Chemometric Analysis of the Volatile Compounds Generated by Aspergillus carbonarius Strains Isolated from Grapes and Dried Vine Fruits
Publisher: MDPI AG
Date: 06-02-2018
Is there no controversy in chromatography?
Publisher: Wiley
Date: 08-2004
Benchmarking of candidate detectors for multiresidue analysis of pesticides by comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 10-2013
DOI: 10.1016/J.CHROMA.2013.08.011
Abstract: The present study discusses the relevance, performance and complementarities of flame photometric detector in phosphorus (FPD/P) and sulfur (FPD/S) modes, micro electron capture detector (μECD), nitrogen phosphorus detector (NPD), flame ionization detector (FID) and time-of-flight mass spectrometer (TOF/MS) for the comprehensive two-dimensional gas chromatography (GC×GC) analysis of pesticides. A mix of 41 pesticides including organophosphorus pesticides, synthetic pyrethroids and fungicides was investigated in order to benchmark GC×GC systems in terms of linearity (R(2)), limits of detection (LOD), and peak shape measures (widths and asymmetries). A mixture of pesticides which contained the heteroatoms phosphorus, sulfur, nitrogen and one or several halogens, was used to acquire a comparative data set to monitor relative detector performances. GC×GC datasets were systematically compared to their GC counterpart acquired with an optimized one-dimensional GC configuration. Compared with FID, considered the most appropriate detector in terms of suitability for GC×GC, the element-selective detector FPD/P and μECD best met the peak widths (0.13-0.27s for FPD/P 0.22-0.26s for μECD) and tailing factors (0.99-1.66 for FPD/P 1.32-1.52 for μECD) NPD exhibited similar peak widths (0.23-0.30s), but exceeded those of the above detectors for tailing factors (1.97-2.13). These three detectors had improved detection limits of 3-7 times and 4-20 times lower LODs in GC×GC mode compared with FID and TOF-MS, respectively. In contrast FPD/S had poor peak shape (tailing factor 3.36-5.12) and much lower sensitivity (10-20 fold lower compared to FPD/P). In general, element-selective detectors with favorable detection metrics can be considered viable alternatives for pesticide determination using GC×GC in complex matrices. The controversial issue of sensitivity enhancement in GC×GC was considered for optimized GC and GC×GC operation. For all detectors, we found no significant LOD enhancement in GC×GC.
Multidimensional gas chromatography investigation of concentration and temperature effects of oxime interconversion on ionic liquid and poly(ethylene glycol) stationary phases
Publisher: Elsevier BV
Date: 11-2019
DOI: 10.1016/J.ACA.2019.07.013
Abstract: This study develops analytical approaches using comprehensive heart-cut multidimensional gas chromatography (H/C MDGC) to experimentally investigate effects of concentration and temperature on peak shapes and on kinetic analysis of E/Z isomerisation of oximes which undergo various extents of interconversion on
The Blossoming of Technology for the Analysis of Complex Aroma Bouquets—A Review on Flavour and Odorant Multidimensional and Comprehensive Gas Chromatography Applications
Publisher: MDPI AG
Date: 31-05-2019
DOI: 10.3390/MOLECULES24112080
Abstract: Multidimensional approaches in gas chromatography have been established as potent tools to (almost) attain fully resolved analyses. Flavours and odours are important application fields for these techniques since they include complex matrices, and are of interest for both scientific study and to consumers. This article is a review of the main research studies in the above theme, discussing the achievements and challenges that demonstrate a maturing of analytical separation technology.
Multiple component isolation in preparative multidimensional gas chromatography with characterisation by mass spectrometry and nuclear magnetic resonance spectroscopy
Publisher: Elsevier BV
Date: 07-2009
DOI: 10.1016/J.CHROMA.2009.06.006
Abstract: The preparative scale isolation of multiple components from an essential oil matrix is described using multidimensional gas chromatography (prep-MDGC) which allows their further characterisation by mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy. Menthol, linalyl acetate, carvone and geraniol were isolated in idually, and were also collected in various combinations. It was demonstrated to be possible to collect multiple selected components from numerous repeat injections of the s le, to permit increased mass recovery from an external cryotrap collection device. Peak retention times remained reproducible (<0.3s) over the repeated injections and switching events. This methodology may be utilised to confirm peak identity or to produce unique mixed-component reference standards, for instance to allow their identification in other s les using GC/MS, or identify them in comprehensive two-dimensional gas chromatography (GCxGC) analysis.
High temperature multidimensional gas chromatographic approach for improved separation of triacylglycerols in olive oil
Publisher: Elsevier BV
Date: 05-2018
DOI: 10.1016/J.CHROMA.2018.03.037
Abstract: Heart-cut multidimensional gas chromatographic (H/C MDGC) methods under suitable flow and high temperature (T) program conditions were developed to separate olive oil triacylglycerols (TAGs). Different column sets were selected for further evaluation, each with relatively short non-polar first dimension (
Essential-oil analysis of irradiated spices by using comprehensive two-dimensional gas chromatography
Publisher: Wiley
Date: 21-05-2014
Dual-injection system with multiple injections for determining bidimensional retention indexes in comprehensive two-dimensional gas chromatography
Publisher: American Chemical Society (ACS)
Date: 05-01-2008
DOI: 10.1021/AC071367Q
Abstract: A new instrumental approach for collection of retention index data in the first (1D) and second (2D) dimensions of a comprehensive two-dimensional (2D) gas chromatography (GCxGC) experiment has been developed. First-dimension indexes were determined under conventional linear programmed temperature conditions (Van den Dool indexes). To remove the effect that the short secondary column imposes on derived 1D indexes, as well as to avoid handling of pulsed GCxGC peaks, the proposed approach uses a flow splitter to ert part of the primary column flow to a supplementary detector to simultaneously generate a conventional 1D chromatogram, along with the GCxGC chromatogram. The critical 2D indexes (KovAts indexes) are based upon isovolatility curves of normal alkanes in 2D space, providing a reference scale against which to correlate each in idual target peak throughout the entire GCxGC run. This requires the alkanes to bracket the analytes in order to allow retention interpolation. Exponential curves produced in the 2D separation space require a novel approach for delivery of alkane standards into the 2D column by using careful solvent-free solid-phase microextraction (SPME) s ling. Sequential introduction of alkane mixtures during GCxGC runs was performed by thermal desorption in a second injector which was directly coupled through a short transfer line to the entrance of the secondary column, just prior to the modulator so that they do not have to travel through the 1D column. Thus, each alkane mixture injection was quantitatively focused by the cryogenic trap, then launched at predetermined times onto the 2D column. The system permitted construction of an alkane retention map upon which bidimensional indexes of a 25-perfume ingredient mixture could be derived. Comparison of results with indexes determined in temperature-variable one-dimensional (1D) GC showed good correlation. Plotting of the separation power in the second dimension was possible by mapping Trennzahl values throughout the 2D space. The methodology was applied to the separation of a standard mixture composed of 25 analytes (very erse in polarity and structure) suspected to be allergens in perfume s les. The method will allow straightforward determination of temperature-variable retention indexes of target analytes.
Molecular structure retention relationships in comprehensive two-dimensional gas chromatography
Publisher: Wiley
Date: 11-2004
Abstract: Comprehensive two‐dimensional gas chromatography (GC×GC) offers new opportunities to develop relationships between molecular structure and retentions in the two dimensional (2D) separation space defined by the GC×GC retention in each dimension. Whereas single dimension GC provides only one retention property for a solute, and hence the specific relationship between retention and chemical property is not readily apparent or derivable, the 2D presentation of compounds in GC×GC provides a subtle and exquisite correlation of chemical property and retention unlike any other GC experiment. The ‘orthogonality’ of the two separation dimensions is intimately related to the manner in which different separation mechanisms, available through use of two dissimilar phases, are accessible to the different chemical compounds or classes in a s le mixture, and indeed the specific chemical classes present in the s le. The GC×GC experiment now permits various processes such as chemical decompositions, molecular interconversions, various non‐linear chromatography effects, and processes such as slow reversible interactions that may arise with stationary phases or in the injector or column couplings, to be identified and further investigated. Here, we briefly review implementation of the GC×GC method, consider the molecular selectivity of GC×GC, and highlight a selection of molecular processes that can be probed by using GC×GC.
Application of comprehensive two-dimensional gas chromatography to drugs analysis in doping control
Publisher: Elsevier BV
Date: 06-2003
DOI: 10.1016/S0021-9673(02)01998-2
Abstract: Comprehensive two-dimensional gas chromatography (GC x GC) now occupies a niche within the GC technology regime. The technique is undeniably unique in the manner in which the experiment is conducted, the way results are presented and the interpretive opportunities offered. For the 1000th volume of this journal it is appropriate to expand upon these features, and review the progress made in GC x GC to date. Firstly, brief general comment is made on multidimensional procedures, and to review key aspects of GC x GC. The use of the targeted multidimensional GC method allows absolute retentions in the second dimension of a GC x GC experiment to be estimated, and also offers a novel way to obtain enhanced response for resolved solutes. Then, to illustrate the utility of the technique, the application of GC x GC to the screening of drugs and their metabolites in biological fluids is described using prolintane metabolites in canine urine as an ex le, with s les taken at four time intervals after administration. This ex le illustrates the first application of GC x GC in the field of forensic toxicology, an area traditionally dominated by GC-MS. Most drug compounds were found to be retained on the 0.8-m second column for a greater time than the modulation period (3 s) used for initial analysis, under the conditions described. Hence a 0.4-m D2 BPX50 (50% phenyl methyl polysilphenylene) column was then used throughout, with most compounds retained less than 4 s. For the standard drug mixture, three overlapping drugs on the first dimension column (BPX5) were subsequently baseline resolved on the BPX50 column. For prolintane administration s les, the parent drug and metabolites could be effectively resolved from background matrix peaks. Likewise a 23-drug spike standard in horse urine blank gave acceptable resolution of the drugs from matrix peaks.
Projection of multidimensional GC data into alternative dimensions-exploiting sample dimensionality and structured retention patterns
Publisher: Springer Science and Business Media LLC
Date: 25-05-2006
DOI: 10.1007/S00216-006-0481-7
Abstract: Comprehensive multidimensional gas chromatography (GCxGC) is a powerful separation technique. One of the features of this technique is that it offers separations with more apparent structure than that offered by conventional one-dimensional GC (1-D GC). While some previous studies have alluded to this structure, and used structured retention patterns for some simple classifications, the topic of structured retention in GCxGC has not been studied in any great detail. Using the separation of fatty acid methyl esters (FAME) on both nonpolar olar and polar/nonpolar column sets, the interaction between the separation dimensions and the s le dimensions is explored here. The GCxGC separation of a series of compounds is presented as a projection of the s le from s le space, a p-dimensional space with dimensions defined by the dimensionality of the s le, into separation space: for GCxGC, a two-dimensional plane passing through the s le space in an orientation defined by the separation conditions. Using this conceptual model and some a priori knowledge of the s le, it is shown how the image of the s le in the separation space can be used to construct an image of the s le in alternate dimensions, such as second dimension retention factor ((2)k) vs. chain length in the case of FAME. These projections into alternate dimensions should facilitate the interpretation of the complex patterns found within the GCxGC chromatogram for the identification and classification of compounds.
Biometric, nutritional and sensory characteristic modifications in farmed Murray cod (Maccullochella peelii peelii) during the purging process
Publisher: Elsevier BV
Date: 02-2009
Applications of comprehensive two-dimensional gas chromatography to the characterization of petrochemical and related samples
Publisher: Elsevier BV
Date: 02-2006
DOI: 10.1016/J.CHROMA.2005.09.036
Abstract: This article discusses the application of comprehensive two-dimensional gas chromatography (GC x GC) to s les derived from petrochemicals. The use of GC x GC for characterization of petroleum and petroleum derivatives, through group type analysis, such as benzene, toluene, ethylbenzene, xylenes (BTEX), total aromatic hydrocarbons, polyaromatic hydrocarbons, and heteroatomic sulfur-, oxygen-, and nitrogen-containing compounds is presented. The capability of GC x GC to provide additional chemical-specific information regarding petroleum-processing steps, such as linear alkanes dehydrogenation, Fischer-Tropsch process, hydrogenation and oligomerization, is also described. In addition, GC x GC analyses of petrochemical biomarkers and environmental petrochemical-derived pollutants are reported. The role of comparison of s les through use of simple fingerprint approaches is highlighted.
Comparison of the performance of different silica hydride particles for the solid-phase extraction of non-volatile analytes from dark chocolate with analysis by gas chromatography-quadrupole mass spectrometry
Publisher: Elsevier BV
Date: 05-2015
DOI: 10.1016/J.FOODCHEM.2014.10.083
Abstract: The extraction capabilities of a Diamond Hydride™ phase, as well as silica hydride phases modified with bidentate octadecyl (BDC(18)), phenyl or cholesteryl groups, were evaluated for the analysis of fatty acids, amino acids, sugars and sterols in a dark chocolate extract. These batch adsorption performances were investigated using either methanol or aqueous methanol as the solvent. The compositions of the extracted fractions were assessed by gas chromatography interfaced with quadrupole mass spectrometry (GC-qMS). The batch binding propensities of the various compound classes with silica hydride particles modified with immobilised phenyl groups or larger ligands followed trends predicted from linear solvation energy relationships. Both prediction and experiment revealed that better extraction results could be obtained with the phenyl, BDC(18) and cholesteryl hydride particles for the major chocolate components. Based on these results, separations in micro-pipette tip format with these three types of stationary phase particles have been undertaken.
Effect of Activated Sludge Microparticles on Pesticide Partitioning Behavior
Publisher: American Chemical Society (ACS)
Date: 10-1994
DOI: 10.1021/ES00060A023
Multidimensional and comprehensive two-dimensional gas chromatography of dichloromethane soluble products from a high sulfur Jordanian oil shale
Publisher: Elsevier BV
Date: 03-2014
DOI: 10.1016/J.TALANTA.2013.11.069
Abstract: A high sulfur Jordanian oil shale was converted into liquid hydrocarbons by reaction at 390 °C under N2, and the dichloromethane soluble fraction of the products was isolated then analyzed by using gas chromatography (GC). Comprehensive two-dimensional GC (GC×GC) and multidimensional GC (MDGC) were applied for component separation on a polar - non-polar column set. Flame-ionization detection (FID) was used with GC×GC for general s le profiling, and mass spectrometry (MS) for component identification in MDGC. Multidimensional GC revealed a range of thiophenes (th), benzothiophenes (bth) and small amounts of dibenzothiophenes (dbth) and benzonaphthothiophenes (bnth). In addition, a range of aliphatic alkanes and cycloalkanes, ethers, polar single ring aromatic compounds and small amounts of polycyclic aromatics were also identified. Some of these compound classes were not uniquely observable by conventional 1D GC, and certainly this is true for many of their minor constituent members. The total number of distinct compounds was very large (ca.>1000). GC×GC was shown to be appropriate for general s le profiling, and MDGC-MS proved to be a powerful technique for the separation and identification of sulfur-containing components and other polar compounds.
Chapter 8 Gas chromatography
Publisher: Elsevier
Date: 2004
Effects of starvation and water quality on the purging process of farmed murray cod (Maccullochella peelii peelii)
Publisher: American Chemical Society (ACS)
Date: 11-09-2008
DOI: 10.1021/JF801286N
Abstract: The aim of this study was to determine the effects of starvation and water quality during the purging process on the biometric parameters, fatty acids, and flavor volatiles of Murray cod farmed in a recirculation system. Market size Murray cod, at the end of the grow-out stage, were ided into eight treatments. The treatments were either fed/starved (F or S) and kept in clean water (CW: CWF2, CWS2, CWF4, and CWS4) or fed/starved and kept in recycled water (RW: RWF2, RWS2, RWF4, and RWS4) for either 2 or 4 weeks. Fish were s led at 0, 2, and 4 week intervals. Food deprivation was responsible for a significant (P < 0.05) weight loss compared to that of fed treatments. The same was observed for the condition factor (K), hepatosomatic index (HSI), and dress-out percentage (DP). No significant changes were, however, observed in the visceral fat index (VFI). Saturated fatty acids (SFA) were highest in RWF4 and lowest in CWS4 (P < 0.05), while monounsaturated fatty acids (MUFA) were lowest in CWF4 (P < 0.05). Starvation did not affect the flavor volatile compounds, which were mainly affected by changes in water quality. Specifically, total aldehyde (% w/w) content was significantly (P < 0.05) affected by water quality, but the time of purging was not responsible for any noteworthy differences. This study was able to separate the effects of starvation and water quality, in the purging process, on the final eating quality of farmed market size Murray cod. It is concluded that because of the inevitable weight loss during starvation, Murray cod should be fed during the purging stage but kept in clean water and deprived of food only for the time necessary to empty the gastro-intestinal tract.
Continuum in MDGC Technology: From Classical Multidimensional to Comprehensive Two-Dimensional Gas Chromatography
Publisher: American Chemical Society (ACS)
Date: 22-03-2016
DOI: 10.1021/ACS.ANALCHEM.5B03839
Abstract: Recent advances in multidimensional gas chromatography (MDGC) comprise methods such as multiple heart-cut (H/C) analysis and comprehensive two-dimensional gas chromatography (GC × GC) however, clear approaches to evaluate the MDGC results, choice of the most appropriate method, and optimized separation remain of concern. In order to track the capability of these analytical techniques and select an effective experimental approach, a fundamental approach was developed utilizing a time summation model incorporating temperature-dependent linear solvation energy relationship (LSER). The approach allows prediction of optimized analyte distribution in the 2D space for various MDGC approaches employing different experimental variables such as column lengths, temperature programs, and stationary phase combinations in order to evaluate separation performance (apparent (1)D, (2)D, total number of separated peaks, and orthogonality) for simulated MDGC results. The methodology applied LSER to generate results for nonpolar-polar and polar-nonpolar 2D column configurations for separation of 678 compounds in an oxidized kerosene-based jet fuel s le. Three-dimensional plots were generated in order to illustrate the dependency of separation performance on (2)D column length and number of injections for different stationary phase combinations. With a given limit of analysis time, a MDGC approach to obtain an optimized total separated peak number for a particular column set was proposed depending on (1)D and (2)D analyte peak distribution. This study introduces fundamental concepts and establishes approaches to design effective GC × GC or multiple H/C systems for different column combinations, to provide the best overall separation outcomes with the highest separated peak number and/or orthogonality.
Approaches and Challenges for Analysis of Flavor and Fragrance Volatiles
Publisher: American Chemical Society (ACS)
Date: 17-08-2017
The nobel prize 2002 - Molecular analysis rewarded
Publisher: Wiley
Date: 2003
Organophosphorus pesticide and ester analysis by using comprehensive two-dimensional gas chromatography with flame photometric detection
Publisher: Elsevier BV
Date: 12-2013
DOI: 10.1016/J.JHAZMAT.2013.10.048
Abstract: Thirty-seven phosphorus (P)-containing compounds comprising organophosphorus pesticides and organophosphate esters were analyzed by using comprehensive two-dimensional gas chromatography with flame photometric detection in P mode (GC × GC-FPD(P)), with a non-polar/moderately polar column set. A suitable modulation temperature and period was chosen based on experimental observation. A number of co-eluting peak pairs on the (1)D column were well separated in 2D space. Excellent FPD(P) detection selectivity, responding to compounds containing the P atom, produces clear 2D GC × GC plots with little interference from complex hydrocarbon matrices. Limits of detection (LOD) were within the range of 0.0021-0.048 μmol L(-1), and linear calibration correlation coefficients (R(2)) for all 37 P-compounds were at least 0.998. The P-compounds were spiked in 2% diesel and good reproducibility for their response areas and retention times was obtained. Spiked recoveries were 88%-157% for 5 μg L(-1) and 80%-138% for 10 μg L(-1) spiked levels. Both (1)tR and (2)tR shifts were noted when the content of diesel was in excess of 5% in the matrix. Soil s les were analyzed by using the developed method some P-compounds were positively detected. In general, this study shows that GC × GC-FPD(P) is an accurate, sensitive and simple method for P-compound analysis in complicated environmental s les.
Evaluation of fast enantioselective multidimensional gas chromatography methods for monoterpenic compounds: Authenticity control of Australian tea tree oil
Publisher: Elsevier BV
Date: 08-2015
DOI: 10.1016/J.CHROMA.2015.06.036
Abstract: This work demonstrates the potential of fast multiple heart-cut enantioselective multidimensional gas chromatography (GC-eGC) and enantioselective comprehensive two-dimensional gas chromatography (eGC×GC), to perform the stereoisomeric analysis of three key chiral monoterpenes (limonene, terpinen-4-ol and α-terpineol) present in tea tree oil (TTO). In GC-eGC, separation was conducted using a combination of mid-polar first dimension ((1)D) column and a chiral second dimension ((2)D) column, providing interference-free enantioresolution of the in idual antipodes of each optically active component. A combination of (1)D chiral column and (2)D polar columns (ionic liquid and wax phases) were tested for the eGC×GC study. Quantification was proposed based on summation of two major modulated peaks for each antipode, displaying comparable results with those derived from GC-eGC. Fast chiral separations were achieved within 25min for GC-eGC and<20min for eGC×GC, while ensuring adequate interference-free enantiomer separation. The suitability of using these two enantioselective multidimensional approaches for the routine assessment of chiral monoterpenes in TTO was evaluated and discussed. Exact enantiomeric composition of chiral markers for authentic TTOs was proposed by analysing a representative number of pure TTOs sourced directly from plantations of known provenance in Australia. Consistent enantiomeric fractions of 61.6±1.5% (+):38.4±1.5% (-) for limonene, 61.7±1.6% (+):38.3±1.6% (-) for terpinen-4-ol and 79.6±1.4% (+):20.4±1.4% (-) for α-terpineol were obtained for the 57 authentic Australian TTOs. The results were compared (using principle component analysis) with commercial TTOs (declared as derived from Melaleuca alternifolia) obtained from different continents. Assessing these data to determine adulteration, or additives that affect the enantiomeric ratios, in commercially sourced TTOs is discussed. The proposed method offers distinct advantages over eGC, especially in terms of analysis times and selectivity which can serve as a reliable platform for authenticity control of TTO.
Studies on thermionic ionisation detection in comprehensive two-dimensional gas chromatography
Publisher: Wiley
Date: 10-2006
Abstract: This study explores the application of specific thermionic ionisation detection in comprehensive 2-D GC (GC x GC) and represents the first report of GC x GC with nitrogen phosphorus detection (GC x GC-NPD). Of particular interest is the performance of the NPD with respect to peak parameters of asymmetry and sensitivity. Since GC x GC produces much narrower peaks than obtained with fast GC (e.g. 100 ms vs. <1 s) the effect of detector response time and any lack of symmetry arising from the detection step is important if peak separation (resolution) is to be maintained. It was observed that detector gas flows had a significant impact on peak asymmetry and peak magnitude, and that optimisation of the detector was critical, particularly for complex s le analysis by GC x GC-NPD. Peak asymmetries ranging from As = 1.8 to 8.0 were observed under different conditions of detector gas flows. Comparison of GC x GC-NPD with GC x GC-flame ionisation detection (FID) showed the former to be approximately 20 times more sensitive for the detection of nitrogen-containing methoxypyrazines analytes, and GC x GC-NPD had a larger linear detection range compared to GC x GC-FID. Furthermore, comparison of GC x GC-NPD and GC x GC-TOFMS chromatograms for the analysis of coffee head-space demonstrated the benefits of selective detection, ultimately realised in a comparatively simplified contour plot.
Enantiomeric distribution of selected terpenes for authenticity assessment of Australian Melaleuca alternifolia oil
Publisher: Elsevier BV
Date: 05-2015
Universal method for online enrichment of target compounds in capillary gas chromatography using in-oven cryotrapping
Publisher: American Chemical Society (ACS)
Date: 09-08-2011
DOI: 10.1021/AC200973Z
Abstract: A method is described that permits automated online enrichment of injected compounds in multidimensional gas chromatography by using a microfluidic heart-cut (H-C) device to direct target compounds into a cryogenically cooled internal trap (cryotrap, CT). By performing multiple injections of a s le, selected compounds or regions of a primary column separation can be collected in the CT. Remobilizing the trapped species allows elution and further resolution on the second column. Using a well-balanced H-C device, compounds can be fully excluded from the collection step or quantitatively transferred to the CT. Peak areas of the remobilized compound correlate well with the number of s le injections. Trapping on various column phases shows the method is suited to quantitative trapping of alkanes of mass greater than about dodecane and fatty acid methyl esters greater than the C8 homologue. Caffeine and menthol standards of concentration 100 μg mL(-1) gave peak area correlation coefficients for 1-10 and 1-50 replicate split injections of 1 μL volume of 0.999 and 0.996, respectively. Peak height correlations were less favorable as a result of peak broadening on the second column, presumably due to overloading at greater collected mass. The method was applied to 0.2% solutions of peppermint oil (menthol a major component 44%) and 1.0% lavender oil (α-terpineol and neryl acetate minor components of 1.05 and 0.42% abundance). The minor components gave good area and height correlations, and good recovery around 90% was observed for menthol compounds recovered from 15 accumulations. Response lification was further demonstrated for menthol from mint oil headspace s ling using solid phase microextraction. This approach should be a valuable adjunct for improved detection specificity, for detectors of low sensitivity, and when prior s le concentration provides insufficient response of selected target analytes.
The retention behaviour of amino acids in hydrophilic interaction liquid chromatography on zwitterionic stationary phases
Publisher: Wiley
Date: 18-06-2013
Abstract: The retention behaviour of amino acids was studied in hydrophilic LC on zwitterionic stationary phases. Evaluation of the influences of acetonitrile/water content, ammonium acetate (NH4Ac) concentration and mobile phase pH values was performed. Fourteen amino acids were tested and they were all retained to varying extents, with poorer retention in high water content eluents. The linear relationship between the logarithm of retention factor and log(water content) indicated that adsorption dominated or at least was partly involved in the separation mechanism. Electrostatic and hydrophilic interactions also contributed to the retention of these amino acids under different separation conditions with various mobile phase pH values and NH4Ac concentrations. Thus, the overall retention mechanism could be explained as a combination of adsorption, electrostatic and hydrophilic interactions. The magnitude and contribution of each mechanism is dependent on the nature of the analyte and the separation conditions applied.
Effects of variation in modulator temperature during cryogenic modulation in comprehensive two-dimensional gas chromatography
Publisher: Wiley
Date: 09-2009
Abstract: Many modulation systems in comprehensive 2D GC (GC x GC) are based on cryogenic methods. High trapping temperatures in these systems can result in ineffective trapping of the more volatile compounds, whilst temperatures that are too low can prevent efficient remobilisation of some compounds. To better understand the trapping and release of compounds over a wide range of volatilities, we have investigated a number of different constant temperature modulator settings, and have also examined a constant temperature differential between the cryo-trap and the chromatographic oven. These investigations have led us to modify the temperature regulation capabilities of the longitudinally modulated cryogenic system (LMCS). In contrast to the current system, where the user sets a constant temperature for the cooling chamber, the user now sets the temperature difference between the cryo-trap and the chromatographic oven. In this configuration, the cooling chamber temperature increases during the chromatographic run, tracking the oven temperature r . This produces more efficient, volatility-dependent modulation, and increases the range of volatile compounds that can be analysed under optimal trap-and-release conditions within a single analytical run. This system also reduces cryogenic fluid consumption.
Comprehensive two-dimensional gas chromatrography - GC x GC
Publisher: Wiley
Date: 04-2004
HTC-8 Eighth International Symposium on Hyphenated Techniques in Chromatography and Hyphenated Chromatographic Analyzers
Publisher: Wiley
Date: 03-2004
Comprehensive two-dimensional gas chromatography: Application to aroma and essential oil analysis
Publisher: American Chemical Society
Date: 30-09-2008
Quantitation of suspected allergens in fragrances (Part I): Evaluation of comprehensive two-dimensional gas chromatography for quality control
Publisher: Wiley
Date: 03-2004
DOI: 10.1002/FFJ.1334
Simultaneous estimation of retention times of overlapping primary peaks in comprehensive two-dimensional GC
Publisher: Wiley
Date: 09-07-2013
Abstract: A general approach is developed to estimate the retention time (t(R)) of overlapping primary peaks in comprehensive 2D GC without assumptions such as the limitation of modulation ratio or symmetry of the target primary peak. Accurate determination of t(R) can recover the original peak profile by using mathematical fitting. First, the modulation pattern of the first-dimension peak in the second dimension is summarized with the number of major modulation fractions equal to or less than four. A novel formula to derive t(R) is defined and separately investigated for cases of modulation number for 1-4, on the basis of the center of gravity of all fractions of the primary peak, in the second dimension. A moving-window search strategy is further developed for peak clusters overlapping in both separation dimensions, to extract first dimension tR of pure components with the same second dimension time after data pretreatment (background subtraction time shift correction). Results are very close to the times of simulated comprehensive 2D GC separations. Compared to methods such as reconstruction of original chromatographic profiles to derive t(R), the proposed approach balances the precision, and ease of adaption to real applications.
Concepts and preliminary observations on the triple-dimensional analysis of complex volatile samples by using GC×GC-TOFMS
Publisher: American Chemical Society (ACS)
Date: 10-02-2001
DOI: 10.1021/AC000987N
Modulation-induced error in comprehensive two-dimensional gas chromatographic separations
Publisher: Elsevier BV
Date: 07-2008
DOI: 10.1016/J.CHROMA.2008.03.008
Abstract: There is a fundamental difference between data collected in comprehensive two-dimensional gas chromatographic (GCxGC) separations and data collected by one-dimensional GC techniques (or heart-cut GC techniques). This difference can be ascribed to the fact that GCxGC generates multiple sub-peaks for each analyte, as opposed to other GC techniques that generate only a single chromatographic peak for each analyte. In order to calculate the total signal for the analyte, the most commonly used approach is to consider the cumulative area that results from the integration of each sub-peak. Alternately, the data may be considered using higher order techniques such as the generalized rank annihilation method (GRAM). Regardless of the approach, the potential errors are expected to be greater for trace analytes where the sub-peaks are close to the limit of detection (LOD). This error is also expected to be compounded with phase-induced error, a phenomenon foreign to the measurement of single peaks. Here these sources of error are investigated for the first time using both the traditional integration-based approach and GRAM analysis. The use of simulated data permits the sources of error to be controlled and independently evaluated in a manner not possible with real data. The results of this study show that the error introduced by the modulation process is at worst 1% for analyte signals with a base peak height of 10xLOD and either approach to quantitation is used. Errors due to phase shifting are shown to be of greater concern, especially for trace analytes with only one or two visible sub-peaks. In this case, the error could be as great as 6.4% for symmetrical peaks when a conventional integration approach is used. This is contrasted by GRAM which provides a much more precise result, at worst 1.8% and 0.6% when the modulation ratio (MR) is 1.5 or 3.0, respectively for symmetrical peaks. The data show that for analyses demanding high precision, a MR of 3 should be targeted as a minimum, especially if multivariate techniques are to be used so as to maintain data density in the primary dimension. For rapid screening techniques where precision is not as critical lower MR values can be tolerated. When integration is used, if there are 4-5 visible sub-peaks included for a symmetrical peak at MR=3.0, the data will be reasonably free from phase-shift-induced errors or a negative bias. At MR=1.5, at least 3 sub-peaks must be included for a symmetrical peak. The proposed guidelines should be equally relevant to LCxLC and other similar techniques.
Multidimensional gas chromatography methods for bioanalytical research
Publisher: Future Science Ltd
Date: 09-2014
DOI: 10.4155/BIO.14.186
Abstract: Multidimensional gas chromatography (MDGC) methods are high-resolution volatile chemical separation techniques, and comprise classical heart-cutting MDGC and its more recent incarnation, comprehensive 2D GC. Although available for a long period, MDGC approaches are still not widely practiced in the field of bioanalysis, possibly reflecting the general preference for regular GC versus MDGC approaches. With the recent introduction of ‘-omic’ techniques that emphasize global nontargeted profiling of metabolites within living systems, it is evident that MDGC is gaining momentum as a separation tool, since it offers very high resolution. By untangling metabolites within highly complex biological matrices, and expanding the metabolic coverage, MDGC plays a frontline role in ‘-omics’ based studies. This review highlights state-of-the-art MDGC approaches, and summarizes the recent developments in bioanalytics.
Comprehensive two-dimensional gas chromatography, retention indices and time-of-flight mass spectra of flavonoids and chalcones
Publisher: Elsevier BV
Date: 12-2010
DOI: 10.1016/J.CHROMA.2010.10.093
Abstract: The applicability of comprehensive two-dimensional gas chromatography (GC×GC) for flavonoids analysis was investigated by separation and identification of flavonoids in standards, and a complex matrix natural s le. The modulation temperature was optimized to achieve the best separation and signal enhancement. The separation pattern of trimethylsilyl (TMS) derivatives of flavonoids was compared on two complementary column sets. Whilst the BPX5/BPX50 (NP/P) column set offers better overall separation, BPX50/BPX5 (P/NP) provides better peak shape and sensitivity. Comparison of the identification power of GC×GC-TOFMS against both the NIST05 MS library and a laboratory (created in-house) TOFMS library was carried out on a flavonoid mixture. The basic retention index information on high-performance capillary columns with a non-polar stationary phase was established and database of mass spectra of trimethylsilyl derivatives of flavonoids was compiled. TOFMS coupled to GC×GC enabled satisfactory identification of flavonoids in complex matrix s les at their LOD over a range of 0.5-10 μg/mL. Detection of all compounds was based on full-scan mass spectra and for each compound a characteristic ion was chosen for further quantification. This study shows that GC×GC-TOFMS yields high specificity for flavonoids derived from real natural s les, dark chocolate, propolis, and chrysanthemum.
Marine fragrance chemistry
Publisher: Wiley
Date: 06-2008
Abstract: The main marine message in perfumery is projected by Calone 1951 (7-methyl-2H-1,5-benzodioxepin-3(4H)-one). Kraft (Givaudan) and Gaudin (Firmenich) further maximized the marine fragrance molecular membership by extending the carbon chain of the 7-Me group. Our research targeted the polar group of the benzodioxepinone parent compound to investigate how this region of molecular makeup resonates with the dominant marine fragrance of the Calone 1951 structure. The olfactory evaluation of analogues prepared by chemical modification or removal of the CO group resulted in the introduction of aldehydic, sweet and floral-fruity notes with a diluted/diminished potency of the marine odor. To further analyze the olfactory properties of benzodioxepinones containing a erse range of aromatic ring substituents, a novel synthesis route was developed. We found that a 7-alkyl group in Calone 1951 was essential for the maintenance of the significant marine odor characteristic, and our studies support the concept that the odorant structure occupying the hydrophobic binding pocket adjacent to the aromatic ring-binding site of the olfactory receptor is pivotal in the design and discovery of more potent and characteristic marine fragrances. How the structure of benzodioxepinones connects to marine sea-breeze fragrances is our continuing challenging research focus at the chemistry-biology interface.
Advanced gas chromatography and mass spectrometry technologies for fatty acids and triacylglycerols analysis
Publisher: Elsevier BV
Date: 08-2020
Application of pentafluorophenyldimethylsilyl derivatization for gas chromatography-electron-capture detection of supercritically extracted sterols
Publisher: Elsevier BV
Date: 06-1998
Lipase-catalysed esters synthesis of cafestol and kahweol
Publisher: Elsevier BV
Date: 09-2018
DOI: 10.1016/J.FOODCHEM.2018.03.111
Abstract: Cafestol and kahweol (C&K), two coffee diterpene alcohols with structural similarity which exhibit anticarcinogenic effects, were isolated from green coffee Arabica beans, followed by their lipase-catalysed esterification and purification by preparative high-performance liquid chromatography (HPLC). The isolation and enzymatic synthesis parameters of C&K esters were studied, with the latter optimised by a Central Composite Design both procedures were monitored by gas chromatography. Scale up and improved isolation conditions resulted in 1.29 g of C&K, with 98% purity from 300 g of green Arabica beans. The highest C&K ester yields were observed using an alcohol:fatty acid molar ratio of 1:5, 73.3 mg mL
Identification of aroma-active volatiles in banana Terra spirit using multidimensional gas chromatography with simultaneous mass spectrometry and olfactometry detection
Publisher: Elsevier BV
Date: 04-2015
DOI: 10.1016/J.CHROMA.2015.02.029
Abstract: Fruit spirits have been produced and consumed throughout the world for centuries. However, the aroma composition of banana spirits is still poorly characterised. We have investigated the aroma-impact compounds of the banana Terra spirit for the first time, using multidimensional gas chromatography (MDGC and GC × GC) in a multi-hyphenated system - i.e., coupled to flame ionisation detection (FID), mass spectrometry (MS), and olfactometry (O). Solid-phase microextraction (SPME) was used to isolate the headspace aroma compounds of the banana spirit. The detection frequency (DF) technique was applied and aroma regions, detected in the first column separation at >60% Nasal Impact Frequency (NIF), were screened as target potent odour regions in the s le. Using a polar/non-polar phase column set, the potent odour regions were further subjected to MDGC separation with simultaneous O and MS detection for correlation of the aroma perception with MS data for in idual resolved aroma-impact compounds. GC-O analysis enabled 18 aroma-impact regions to be located as providing volatiles of interest for further study for ex le, those comprising perceptions of flower, whisky, green, amongst others. Compounds were tentatively identified through MS data matching and retention indices in both first and second dimensions. The principal volatile compounds identified in this work, which are responsible for the characteristic aroma of the banana spirit, are 3-methylbutan-1-ol, 3-methylbutan-1-ol acetate, 2-phenylethyl acetate and phenylethyl alcohol. This is the first such study to reveal the major aroma compounds that contribute to banana spirit aroma.
Magnetic solid‐phase extraction of benzoylurea insecticides in tea samples with Fe3O4‐hyperbranched polyester magnetic composite as sorbent
Publisher: Wiley
Date: 06-03-2202
Abstract: In this work, a method for the analysis of benzoylurea insecticides, including hexaflumuron, flufenoxuron, lufenuron and chlorfluazuron, in tea s les by high-performance liquid chromatography with Fe
Optimisation of Fluorescence Detection for Polyaromatic Hydrocarbon Determination by Using High Performance Liquid Chromatography
Publisher: Informa UK Limited
Date: 10-1993
Spherical coordinate representations of solvent composition for liquid chromatography method development using experimental design
Publisher: Elsevier BV
Date: 08-2003
DOI: 10.1016/S0021-9673(03)01021-5
Abstract: One of the major techniques used for the method development of ternary and quaternary high performance liquid chromatography (HPLC) systems has been to use mixture designs, often referred to as "Glajch's Triangle". This technique does not allow for the systematic and simultaneous optimization of other factors such as gradient time, pH and temperature that affect the quality of separations. An alternative approach is to use experimental designs. The condition, however, that the composition of all components of the mobile phase must total 100% presents a problem when trying to mathematically represent ranges of each mobile phase constituent of a ternary or quaternary system. A method is described here, based on spherical coordinate representations, that adheres to the constraints of the mobile phase composition and allows experimental designs, such as central composite and factorial designs, to be applied to the simultaneous optimization of the mobile phase composition. Other factors, in particular temperature and gradient time, can then be included in the design. As a result of applying these designs to the HPLC separation of phenols and corticosteroids, it was found necessary to include three-way interactions between experimental factors in the model. The significance of these interactions shows that they need to be considered in HPLC method development.
Comprehensive 2D gas chromatography–time-of-flight mass spectrometry with 2D retention indices for analysis of volatile compounds in frankincense (Boswellia papyrifera)
Publisher: Springer Science and Business Media LLC
Date: 27-03-2018
DOI: 10.1007/S00216-018-1012-Z
Abstract: Frankincense gum resin secreted from Boswellia papyrifera was analysed by comprehensive 2D gas chromatography hyphenated with accurate mass time-of-flight mass spectrometry (GC×GC-accTOFMS). Direct multiple injection experiments with stepwise isothermal temperature programming were then performed to construct isovolatility curves for reference alkane series in GC×GC. This provides access to calculation of second dimensional retention indices (
Analysis of volatile organic compounds in polyurethane coatings based on Eucalyptus sp. bio-oil pitch using comprehensive two-dimensional gas chromatography (GC × GC)
Publisher: Elsevier BV
Date: 05-2010
Influence of chromatographic conditions on separation in comprehensive gas chromatography
Publisher: Elsevier BV
Date: 07-2002
DOI: 10.1016/S0021-9673(02)00458-2
Abstract: Comprehensive gas chromatography (GC x GC) is now established as a powerful technique, which offers unprecedented separation power. For complex s les, the distribution of peaks in the two-dimensional (2D) space still may need to be optimised. Since temperature (T) is a critical variable, and compounds can be shifted in relative positions on column 1 arising from temperature program rate (rT) changes, and since retention in the second dimension, D2 (2tR) is likewise affected by the prevailing T (elution temperature Te), then any factors which alter Te will affect the extent of separation in D2. Since temperature program and carrier gas velocity rate will affect the Te of the solutes, these two factors are considered in this paper. Apart from these two parameters, results of different stationary phase choice for the second dimension column as well as the second dimension column length are reported. rT is found to have the most profound impact on the Te of solutes and will be more likely to cause an inversion of elution order if such behaviour can occur. Peak widths and 2tR increase with a decrease in Te. On the other hand, flow-rate has less impact on peak widths and 2tR although Te is affected by a change in flow-rate. Specific solute-stationary phase interactions will cause the elution order of certain solutes to be altered, and may be observed when a different stationary phase is employed as the second column, depending on the solute-stationary phase separation mechanism. Experiments conducted on different second dimension column length showed that although a longer column will lead to better separations, wrap-around may confound the separation process and may cause the solutes from sequential modulation events to co-elute. Thus a suitable second dimension column phase and length must be employed in order to obtain good separation. The factors investigated in this study will cause different extents of changes in the solute elution order and solute separations, and will affect the 2D contour presentation.
Analytical problems concerning natural waters
Publisher: Royal Society of Chemistry (RSC)
Date: 1978
DOI: 10.1039/AD9781500052
Insights into the origin of the separation selectivity with silica hydride adsorbents
Publisher: American Chemical Society (ACS)
Date: 06-02-2015
DOI: 10.1021/JP5103753
Abstract: In this study, the surface properties of type-B silica have been compared with an unmodified silica hydride phase, a diamond hydride phase and silica hydride phases modified with bidentate anchored octyl (BDC8), bidentate anchored octadecyl (BDC18), phenyl and cholesteryl groups. Atomic distributions of the surface elemental composition of each type of stationary phase were determined using energy-dispersive X-ray spectroscopy. For the type-B silica, unmodified silica hydride, diamond hydride as well as BDC18 and cholesteryl silica hydride phases, the increase in carbon contents correlated with more negative surface ζ potential values (R(2) = 0.92). The origin of these more negative ζ potentials has been evaluated with mobile phases up to 100% (v/v) methanol content, with this property attributed to either an increase in the amount of adsorbed hydroxide ions or a decrease in the amount of adsorbed protons on the surfaces modified silica hydride phases of higher carbon content. This property of chemically modified silica hydride phases is in accordance with the unique propensity for hydroxide ions to be preferentially adsorbed onto hydrophobic surfaces of low permittivity and effects due to the specific accumulated water molecules associated with the electrical interfacial double layer of the adsorbent.
Gas chromatography of volatile metal dialkyldithiophosphates
Publisher: Elsevier BV
Date: 05-1980
New operational modes for multidimensional and comprehensive gas chromatography by using cryogenic modulation
Publisher: Elsevier BV
Date: 2000
DOI: 10.1016/S0021-9673(99)01061-4
Abstract: Historically, hardware and method-related concerns have limited the use of multidimensional gas chromatography in the routine laboratory. This paper presents a new approach that offers the potential to significantly alter the manner in which multidimensional gas chromatography is conducted, based on the use of a modulated cryogenic trap which can be moved longitudinally along the column. Two columns are directly coupled, and no switching valves are used. It is demonstrated that a heartcut section can be cryofocused and zone-compressed, and then rapidly remobilized at the prevailing column oven temperature without any supplementary heating. A short second dimension column is used, giving fast second dimension analysis. This allows a large number of heartcuts to be programmed for any one analysis. The 'ultimate' manifestation of multidimensional gas chromatography is the comprehensive GC technique (GC X GC). This is now simply effected by performing very rapid heartcuts at intervals on the order of 1/5th of the peak width of primary dimension peaks, and requires that the second dimension be able to complete the analysis of each collected zone on a similar timeframe. This paper uses a semi-volatile aromatic mixture to demonstrate these selected operational modes, that can be achieved with the longitudinal modulation method. The flexibility that arises from this approach is shown by the ability to swap between selected whole-peak enhancement and comprehensive modes during the one analytical run. The increased sensitivity that follows from peak compression is a further advantage, which would be beneficial for trace analysis.
Opportunities for ultra-high resolution analysis of essential oils using comprehensive two-dimensional gas chromatography: A review
Publisher: Wiley
Date: 2003
DOI: 10.1002/FFJ.1225
Free terpene evolution during the berry maturation of five Vitis vinifera L. cultivars
Publisher: Elsevier BV
Date: 08-2016
DOI: 10.1016/J.FOODCHEM.2019.125101
Abstract: Terpenes and their derivatives, terpenoids, are important biomarkers of grape quality as they contribute to flavor and aroma of grape and wine. The evolution of terpene and terpenoids throughout grapevine phenological development cycles is not well understood. The current study investigated the volatile profiles of free terpene and terpenoid of five widely grown Vitis vinifera L. cultivars (Shiraz, Cabernet Sauvignon, Riesling, Chardonnay and Pinot Gris), at different phenological stages from fruit-set to harvest. 17 Monoterpenoids, 3 norisoprenoid and 13 sesquiterpenoids were identified and quantified. Discriminant analysis revealed that for each grape cultivar, free terpene profiles at different E-L stages were distinctive. When integrating total sugar, total terpenes and the cumulated heat index, it could be found that flavor ripening was more consistent with sugar ripening in the warmer vintage 2016. Comparing the two red wine varieties, the overall development patterns of total monoterpenes, norisoprenoids and sesquiterpenes were similar.
GC for flavonoids analysis: Past, current, and prospective trends
Publisher: Wiley
Date: 15-12-2013
Abstract: Flavonoids represent one of the more abundant classes of phytochemicals. They are renowned for their health benefits against age-related ailments and diseases. Several chromatography techniques have underpinned many chemical analysis methods, developed for superior flavonoid separation and identification. Among these, GC is one of the most powerful tools in separation science, providing precise measurement of a wide range of flavonoids. Combined with various detectors - most commonly MS-GC offers a sensitive and accurate tool for quantitative and qualitative flavonoids analysis. This review features developments in the application of GC and MS for flavonoids determination during past decades, progressing to recent developments and considering future trends. The review will highlight the state-of-the-art of GC, with opportunities for multidimensional GC analysis also briefly discussed.
Development of a resolution metric for comprehensive two-dimensional chromatography
Publisher: Elsevier BV
Date: 04-2007
DOI: 10.1016/J.CHROMA.2007.01.109
Abstract: A new resolution metric for two-dimensional chromatography is proposed and tested. This resolution measurement is based on the concept of the (one-dimensional) valley-to-peak ratio, which has been adapted and modified for two-dimensional chromatography. Two questions are considered related to the computation of the resolution of a given (two-dimensional) peak. First, the concept of peak neighbourhood is revised, since it changes drastically from one- to two-dimensional chromatography. In a chromatogram resulting from a two-dimensional analysis, one peak may be surrounded by more than two neighbouring peaks. However, the neighbouring peaks can be remote from the peak or some interfering peaks may be in between. In these cases, it is not meaningful to compute the resolution between them. A method is proposed to determine whether a resolution measurement between two two-dimensional peaks is reasonable. Second, a measurement of the valley-to-peak ratio in two-dimensional chromatography is proposed. The measurement is based on the concept of the saddle point (which is defined for two-dimensional surface plots). A study of the correlation of the valley-to-peak ratio with the error obtained for quantification is presented. The new metric can be used as an estimator of the quantification errors. Also, valley-to-peak ratios can be calculated for one or more target peak(s) to estimate the separation quality of the entire chromatogram. This makes the proposed measurement suitable for optimisation purposes. Although the algorithm was developed for GC x GC, preliminary studies suggested that its application to other two-dimensional separation methods (e.g. LC x LC) should only require minor modification (if any).
Ionic liquid capillary columns for analysis of multi-component volatiles by gas chromatography-mass spectrometry: performance, selectivity, activity and retention indices
Publisher: Springer Science and Business Media LLC
Date: 10-11-2018
DOI: 10.1007/S00216-017-0718-7
Abstract: This study investigates applications and performance evaluation of SLB-IL60, SLB-IL76 and SLB-IL111 columns, in relation to a DB-Wax column, for the analysis of coffee volatile compounds. Both standards and an authentic coffee s le were analysed, with solid-phase microextraction (SPME) s ling of the latter. A cryofocusing method was applied to improve resolution of the earliest eluting peaks using splitless injection SPME s le analysis. The Grob test was used to verify the inertness and efficiency of the columns, helping to understand the interactions between analytes and stationary phases, particularly toward more polar coffee analytes. A DB-5 column was used only in analysis of n-alkanes and Grob test mixtures as an apolar reference. The evaluated ionic liquid columns showed a moderate acid-base character and low inertness for compounds with hydrogen bond capabilities, especially for the hydroxylated analytes, 2,3-butanediol in the Grob test, and furanones and acids in the coffee standards. The columns exhibiting the best resolution and efficiency were DB-Wax and SLB-IL60, both for s les and standards. Although the DB-Wax column is preferred for analysis of coffee volatiles, due to better inertness, the evaluated ionic liquid columns allowed identification of compounds that were not observed in separations with the Wax-phase column in this work. Among these compounds is 3,4-dimethyl-2,5-furandione, seldom reported in the literature of coffee. Proposed improvement by the manufacturer in the inertness of the columns evaluated in this study may lead to better results so future versions of IL phases may be better applied in the separation of target analytes, especially those with basic character. Graphical abstract Illustrative representation of the s le (coffee) and the chemical structures of the stationary phases of the ionic liquid capillary columns used as object of study in the present work.
Photodegradation of parathion
Publisher: Springer Science and Business Media LLC
Date: 05-1987
DOI: 10.1007/BF01616707
Abstract: Although clinical trials have shown benefit from early rehabilitation within the ICU, rehabilitation of patients following critical illness is increasingly acknowledged as an area of clinical importance. However, despite recommendations from published guidelines for rehabilitation to continue following hospital discharge, there is limited evidence to underpin practice during this intermediate stage of recovery. Those patients with ICU-acquired weakness on discharge from the ICU are most likely to benefit from ongoing rehabilitation. Despite this, screening based on strength alone may fail to account for the associated level of physical functioning, which may not correlate with muscle strength, nor address non-physical complications of critical illness. The aim of this review was to consider which patients are likely to require rehabilitation following critical illness and to perform an integrative review of the available evidence of content and nature of exercise rehabilitation programmes for survivors of critical illness following hospital discharge. Literature databases and clinical trials registries were searched using appropriate terms and groups of terms. Inclusion criteria specified the reporting of rehabilitation programmes for patients following critical illness post-hospital discharge. Ten items, including data from published studies and protocols from trial registries, were included. Because of the variability in study methodology and inadequate level of detail of reported exercise prescription, at present there can be no clear recommendations for clinical practice from this review. As this area of clinical practice remains in its relative infancy, further evidence is required both to identify which patients are most likely to benefit and to determine the optimum content and format of exercise rehabilitation programmes for patients following critical illness post-hospital discharge.
Comprehensive two-dimensional gas chromatography for fingerprint pattern recognition in cachaça production
Publisher: Elsevier BV
Date: 15-01-2008
DOI: 10.1016/J.TALANTA.2007.07.021
Abstract: Cachaça s les were studied by means of comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry (GCxGC/TOFMS) during the fermentation process and after ageing in different wood materials. The analyses of the aroma compounds were performed after headspace-solid phase microextraction method (HS-SPME) using an 85microm polyacrylate (PA) fibre. Fingerprint monitoring of the distillation process allowed the easy determination of the turning points of the process and high-resolution comparison of cabeça (head), coração (core) and cauda (tail) fractions. The ageing process in different wood materials was well characterised through fingerprint similarity observations in the absence of a suitable metric for expressing the overall similarity, here we use a visual and retention time comparison to identify co-incident peaks and those that differ between s les. For quality control purposes, a simple observation of the contour plots obtained can thus allow the identification of the type of wood used in the ageing process, and the process of ageing, without further statistical treatment or peak identifications. In this manner, peaks, which discriminated most between the different mixtures studied were readily found, i.e. unique compounds were identified in each stage of the distillation process. Approximate first dimension linear retention indices (LRI) for these identified compounds were calculated in a bi-dimensional polar/non-polar column set in the GCxGC experiment and were used in conjunction with mass spectral library searching for tentative identification. Along the progression of the distillation process, 70 compounds appear to visually discriminate between s les and their retention indices are indicated, presenting good correlation with literature data.
Metabolism of bisphenol A in zebrafish (Danio rerio) and rainbow trout (Oncorhynchus mykiss) in relation to estrogenic response
Publisher: Elsevier BV
Date: 06-2003
DOI: 10.1016/S1532-0456(03)00088-7
Abstract: The kinetics of bisphenol A (BPA) were investigated in zebrafish (Danio rerio) exposed to 100 microg BPA/l. BPA uptake was measured during a 7-day period followed by an elimination phase of similar duration. After 2, 6, 12, 24, 48, 72, 120 and 168 h of uptake/elimination, fish were analysed for their content of BPA, bisphenol A glucuronic acid (BPAGA) and bisphenol A sulfate (BPAS). Within the first 24 h steady state levels of BPA, BPAGA and BPAS were reached and the total body concentrations were calculated to be 569, 12,600 and 39.9 ng/g fish, respectively. Elimination rates of the three compounds in zebrafish were estimated by fitting the data to a compartment model. An initial rapid elimination phase was observed for BPA and BPAS with total body half lives (T(1/2)) of <1.1 h and 30 min, followed by a slower second elimination phase with T(1/2) values of 139 and 71 h, respectively. Excretion of BPAGA occurred from a single compartment with a T(1/2) of 35 h. The steady state concentration of BPA and its metabolites were investigated in rainbow trout (Oncorhynchus mykiss) exposed to 100 microg BPA/l. The toxicokinetic parameters from zebrafish and rainbow trout were compared including previously published data on the rainbow trout. The data indicate that the smaller estrogenic sensitivity observed for the zebrafish may be caused by a more rapid metabolism of BPA in the zebrafish liver.
Chromatographic parameters derived for the non-linear response of a flame photometric detector
Publisher: Springer Science and Business Media LLC
Date: 05-1981
DOI: 10.1007/BF02259266
Ionic liquid phases with comprehensive two-dimensional gas chromatography of fatty acid methyl esters
Publisher: Springer Science and Business Media LLC
Date: 17-02-2018
DOI: 10.1007/S00216-018-0944-7
Abstract: New generation inert ionic liquid (iIL) GC columns IL60i, IL76i and IL111i, comprising phosphonium or imidazolium cationic species, were investigated for separation of fatty acid methyl esters (FAME). In general, the iIL phases provide comparable retention times to their corresponding conventional columns, with only minor selectivity differences. The average tailing factors and peak widths were noticeably improved (reduced) for IL60i and IL76i, while they were slightly improved for IL111i. Inert IL phase columns were coupled with conventional IL columns in comprehensive two-dimensional GC (GC × GC) with a solid-state modulator which offers variable modulation temperature (T
Method for small-molecule discovery based on microscale-preparative multidimensional gas chromatography isolation with nuclear magnetic resonance spectroscopy
Publisher: American Chemical Society (ACS)
Date: 23-07-2008
DOI: 10.1021/AC8007847
Abstract: Absolute chemical identification requires obtaining a pure compound followed by structure elucidation using spectroscopic techniques, principally NMR spectroscopy and mass spectrometry. Classical isolation techniques suffer from insufficient resolution for complex s les, requiring time-consuming fractionation in multiple steps. Here, a novel preparative technique based upon capillary column multidimensional gas chromatography (MDGC) with 2D NMR to resolve, isolate, and identify pure volatile components from a complex s le is described. As a model application, geraniol was isolated from an essential oil matrix using MDGC and quantitatively resolved from 15 partially coeluting compounds from the first column. Geraniol was recovered from 10 (8.6 microg) and 100 injections (77.6 microg purity >99%) for subsequent NMR analysis at 500 and 800 MHz (with cryoprobe). Proton and gCOSY NMR experiments were successfully performed at 12.3 microg/mL (10 injections), while gHSQC and gHMBC NMR experiments were obtained at 110.8 microg/mL (100 injections). This approach is applicable to the biodiscovery of volatile molecular species or, indeed, any volatile compound in a complex matrix that requires confirmation of component identity.
Comprehensive two-dimensional gas chromatography - time-of-flight mass spectrometry and simultaneous electron capture detection/nitrogen phosphorous detection for incense analysis
Publisher: Elsevier BV
Date: 10-2008
Emerging opportunities for flavor analysis through hyphenated gas chromatography
Publisher: American Chemical Society (ACS)
Date: 11-11-2009
DOI: 10.1021/JF9013845
Abstract: Important advances in chemical and flavor knowledge are possible through improved analytical separation and identification. Along with greater separation power, both a more robust analysis and an improved identified s le composition result. In this paper, a number of new integrated methods are explored that permit improved resolution and superior analyses for a range of studies. These methods focus on multidimensional gas chromatography (MDGC), comprehensive two-dimensional gas chromatography (GCxGC), olfactometry, mass spectrometry, and nuclear magnetic resonance (NMR) spectroscopy. The overriding objective is to provide technical solutions that employ the best possible separation of compounds, allowing tools such as olfactometry, mass spectrometry, NMR spectroscopy, and other detectors to provide much better characterization of separated chemical species. Various novel strategies are demonstrated that provide the necessary increased separation power, integrated with specific detection steps. Case studies presented include the sensory-directed identification of a woody odorant in hop essential oil, correlation of compound identifications in coriander leaf, and development of new preparative isolation capabilities using MDGC with NMR spectroscopy.
Characterization of tetra-aryl benzene isomers by using preparative gas chromatography with mass spectrometry, nuclear magnetic resonance spectroscopy, and x-ray crystallographic methods
Publisher: American Chemical Society (ACS)
Date: 04-05-2010
DOI: 10.1021/AC100417H
Abstract: The present study describes a preparative gas chromatographic (GC) approach employed to study a series of products arising from reaction of phenylacetylene with para-substituted aryl-iodides under Sonogashira catalysis conditions. GC analysis resolves the isomers from each reaction however, it cannot provide structural details (their MS data are virtually identical). Since classical liquid chromatography cannot resolve the isomers, preparative-scale GC is the only practical approach to provide further spectroscopic characterization of the isomers. The products are well separated by GC so a single thick-film capillary column is adequate for this case, with operation up to approximately +300 degrees C. By collection of 50+ repeat injections, sufficient material could be isolated for (1)H NMR spectral analysis of the isomers, and for one isomer (isomer I) of a number of analogous related catalytic reaction mixtures, X-ray crystal structure determination enabled complete structural elucidation (absolute configuration) of the substitution pattern of the structure of this isomer. This confirmed isomer I to be the 2-para-aryl-substituted 1,3,5-triphenylbenzene product in all cases. (1)H NMR spectra of isomer I products generally had similar patterns but differed markedly from the second major isomer product (isomer II).
Retention time reproducibility in comprehensive two-dimensional gas chromatography using cryogenic modulation - An intralaboratory study
Publisher: Elsevier BV
Date: 08-2002
DOI: 10.1016/S0021-9673(02)00961-5
Abstract: A survey was conducted to determine the reproducibility of retention times in both the first (D1) and second dimension (D2) axes of the two-dimensional separation space, in the comprehensive two-dimensional gas chromatographic analysis of an essential oil s le using cryogenic modulation. The retention times in the two dimensions for a number of in idual components comprising hydrocarbon, alcohol, ester and ketone chemical classes in a Melaleuca alternifolia essential oil were recorded from replicate analyses using four separate column sets and two identical gas chromatographs. Run-to-run, day-to-day, instrument-to-instrument, and column set-to-column set reproducibility were demonstrated from the experimental design. A total of 60 GC x GC analyses were conducted. The longitudinally modulated cryogenic system produced reproducible modulation start times and consistent modulation phase profiles for in idual components in all experiments, and retention time variations in both dimensions were negligible. The average run-to-run reproducibility of 43 components for six replicate injections was found to be 0.12% RSD in the first dimension, and 0.74% RSD in the second dimension. Day-to-day reproducibility showed statistically "significant" difference (F-test), but this was partly ascribable to the excellent within-day reproducibility that led to apparent day-to-day differences. Confidence in absolute retention times (hence component positions) in the two-dimensional separation space is critical to component identification.
Quantification of trace fatty acid methyl esters in diesel fuel by using multidimensional gas chromatography with electron and chemical ionization mass spectrometry
Publisher: Wiley
Date: 07-06-2016
Abstract: Measurement of contamination of marine and naval diesel fuels (arising from product mixing or adulteration) with biodiesel or fatty acid methyl esters can be problematic, especially at very low levels. A suitable solution for this task for trace amounts of in idual fatty acid methyl esters with resolution and quantification can be achieved by using a multidimensional gas chromatographic approach with electron and chemical ionization mass spectrometric detection. A unique column set comprising a 100 m methyl-siloxane nonpolar first dimension column and high-temperature ionic liquid column in the second dimension enabled identification of in idual fatty acid methyl esters at below the lowest concentrations required to be reported in a diesel fuel matrix. Detection limits for in idual fatty acid methyl esters compounds ranged from 0.5 to 5.0 mg/L, with excellent linearity up to 5000 mg/L and repeatability of the method from 1.3 to 3.2%. The method was applied to the analysis of diesel fuel s les with suspected biodiesel contamination. Contamination at 568 mg/L was calculated for an unknown s le and interpretation of the results permitted the determination of a likely source of the contamination.
The microfluidic Deans switch: 50 years of progress, innovation and application
Publisher: Elsevier BV
Date: 09-2016
Biochemical monitoring of black raspberry (Rubus coreanus Miguel) fruits according to maturation stage by H-1 NMR using multiple solvent systems
Publisher: Elsevier BV
Date: 08-2011
Proposed minimum reporting standards for chemical analysis: Chemical Analysis Working Group (CAWG) Metabolomics Standards Initiative (MSI)
Publisher: Springer Science and Business Media LLC
Date: 12-09-2007
Liquid-phase enantioselective chromatographic resolution using interpenetrated, homochiral framework materials
Publisher: Wiley
Date: 25-07-2014
Abstract: Effective separation of mixtures of enantiomers is of continuing interest in analytical and preparative chromatography, with new materials frequently designed and tested. We report two new enantiomerically pure 2D→3D interpenetrated materials used as stationary liquid chromatographic (LC) phases that are shown to resolve selected racemic mixtures with enantiomeric and chemical selectivity. Dicarboxylate ligands derived from amino acids on naphthalene and perylene cores form 2D frameworks that interpenetrate to give 3D structures. Selectivity is initially tested by uptake from solution subsequent LC methods show that the materials exhibit resolution of racemic analytes in 'micro-columns' and that the two closely related materials show markedly different selectivity for different analytes with much greater activity than the ligands alone. Comparison with a close-packed analogue suggests that the separation activity is largely due to surface effects.
Chemometric analysis of comprehensive two-dimensional gas chromatography data using cryogenic modulation
Publisher: Elsevier BV
Date: 12-2003
Cultivar variations of Australian-grown Danshen (Salvia miltiorrhiza): Bioactive markers and root yields
Publisher: Wiley
Date: 02-2009
Abstract: Danshen (Salvia miltiorrhiza Bunge, Lamiaceae) is a commonly used and highly valued Chinese medicinal herb grown widely in China. In the present work, we studied cultivar variations of Australian-grown Danshen in order to select optimal cultivars for local herbal production. Root yields of seven cultivars, V1-V7, were monitored in a one-year field trial, and bioactive markers, including cryptotanshinone, tanshinone I, tanshinone IIA, and salvianolic acid B, were quantitatively determined using a validated RP-HPLC method. Significant variations were found in root yields, root production efficiencies, and contents of the bioactive marker compounds. Linear correlations were observed among the contents of three tanshinones but not among those of tanshinones and salvianolic acid B. Among the cultivars, V6 was the best cultivar for production of tanshinones, and V4 and V5 were best for production of salvianolic acid B. The findings indicate that it is possible to achieve optimal root yields, and high contents of tanshinones and salvianolic acid B by selecting specific Danshen cultivars.
Enantiomeric separation in comprehensive two-dimensional gas chromatography with accurate mass analysis
Publisher: Wiley
Date: 13-01-2014
DOI: 10.1002/CHIR.22280
Abstract: Chiral comprehensive two-dimensional gas chromatography (eGC×GC) coupled to quadrupole-accurate mass time-of-flight mass spectrometry (QTOFMS) was evaluated for its capability to report the chiral composition of several monoterpenes, namely, α-pinene, β-pinene, and limonene in cardamom oil. Enantiomers in a standard mixture were fully resolved by direct enantiomeric-GC analysis with a 2,3-di-O-methyl-6-t-butylsilyl derivatized β-cyclodextrin phase however, the (+)-(R)-limonene enantiomer in cardamom oil was overlapped with other background components including cymene and cineole. Verification of (+)-(R)-limonene components based on characteristic ions at m/z 136, 121, and 107 acquired by chiral single-dimension GC-QTOFMS in the alternate MS/MSMS mode of operation was unsuccessful due to similar parent/daughter ions generated by interfering or co-eluting cymene and cineole. Column phases SUPELCOWAX, SLB-IL111, HP-88, and SLB-IL59, were incorporated as the second dimension column ((2)D) in chiral GC×GC analysis the SLB-IL59 offered the best resolution for the tested monoterpene enantiomers from the matrix background. Enantiomeric ratios for α-pinene, β-pinene, and limonene were determined to be 1.325, 2.703, and 1.040, respectively, in the cardamom oil s le based on relative peak area data.
Comprehensive Two-Dimensional Gas Chromatography with Mass Spectrometry: Toward a Super-Resolved Separation Technique
Publisher: American Chemical Society (ACS)
Date: 12-08-2020
Separation of positional isomers by the use of coupled shape-selective stationary phase columns
Publisher: Springer Science and Business Media LLC
Date: 13-02-2003
DOI: 10.1007/S00216-003-1768-6
Abstract: The successful separation of 2- and 3-methyl-substituted positional isomers of butanol, butyl acetate, and butanoic acid and its ethyl ester, is reported. These compounds are of interest in the study of wine flavour, however the separation of the 2- and 3-methyl isomers may present problems, and more so in the presence of the wine matrix components, when single capillary column gas chromatography (GC) is used. The strategy to achieve separation was based on the use of shape-selective cyclodextrin derivative (CDD) capillary columns (commonly referred to as chiral columns). These columns provide simultaneous resolution of the enantiomeric pairs of the 2-methyl isomers, and at the same time the ability to separate the 3-methyl isomer from the 2-methyl is achieved in all but the case of the ( S)-2- and 3-methylbutanol. The advantages of using shape-selective columns to perform this study is demonstrated, with coupling of two CDD columns giving improved separations of these compounds. Although these compounds are relatively volatile, cryogenic modulated comprehensive two-dimensional GC was shown to provide good pulsed peak profiles with chiral separation in the first dimension when a thicker film trapping column segment was employed. The components of interest were well separated from other wine matrix components.
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