ORCID Profile
0000-0002-8470-0893
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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 | Analytical spectrometry | Detection And Prevention Of Crime; Security Services | Analytical chemistry | Instrumental methods (excl. immunological and bioassay methods) | Separation science | Sensor Technology (Chemical aspects) | Analytical Spectrometry | Gene Expression | Bacteriology | Manufacturing Processes and Technologies (excl. Textiles) | Protein Targeting And Signal Transduction | Animal Management |
ANZSRC Socio-Economic Objective (SEO)
Chemical sciences | Biological sciences | Scientific instrumentation | Expanding Knowledge in the Chemical Sciences | Law enforcement | Animal Welfare | Animal Protection Chemicals | Sheep - Wool | Scientific Instruments
Related Links
Publications
Development of polydimethylsiloxane-microdiamond composite materials for application as sorptive devices
Publisher: Elsevier BV
Date: 02-2020
DOI: 10.1016/J.CHROMA.2019.460669
Abstract: The development and application of non-porous and porous sorptive rods, comprised of polydimethylsiloxane-microdiamond (PDMS-MD) composites, is reported. The PDMS-MD composites were made porous using inorganic salt (NaCl and NaHCO
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.
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.
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.
Membrane assisted and temperature controlled on-line evaporative concentration for microfluidics
Publisher: Elsevier BV
Date: 02-2017
DOI: 10.1016/J.CHROMA.2016.12.003
Abstract: A membrane evaporation concentrator for continuous flow conditions is introduced. The membrane evaporation concentrator provides nearly 30-fold concentration in less than 60min whilst maintaining solute integrity under different sub-ambient pressure conditions and mild temperatures. To better understand the performance of the concentrator, a theoretical model was developed using caffeine as a model analyte, and used to predict the concentration performance of three target analytes at different conditions. An exponential relationship exists between temperature and concentration factor. By using the model it was determined that a 10-fold concentration (±0.5) can be performed at 56.72±0.07°C and at a flow rate of 10μLmin
Tryptophan metabolism, its relation to inflammation and stress markers and association with psychological and cognitive functioning: Tasmanian Chronic Kidney Disease pilot study
Publisher: Springer Science and Business Media LLC
Date: 10-11-2016
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
Advanced and innovative chromatographic techniques for the study of citrus essential oils
Publisher: Wiley
Date: 2005
DOI: 10.1002/FFJ.1556
Principles and applications of comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 09-2002
Coupled reversed-phase and ion chromatographic system for the simultaneous identification of inorganic and organic explosives
Publisher: Elsevier BV
Date: 05-2011
DOI: 10.1016/J.CHROMA.2011.03.046
Abstract: There are many methods available to detect and positively identify either organic or inorganic explosives separately, however no one method has been developed which can detect both types of explosive species simultaneously from a single s le. In this work, a unique coupled-chromatographic system is reported for the simultaneous determination of both organic and inorganic explosive species and is used for pre-blast analysis/identification purposes. This novel approach is based on the combination of reversed-phase high performance liquid chromatography and ion chromatography which allows trace levels of organic and inorganic explosives to be determined simultaneously from a single s le. Using this procedure, a 20 min reversed-phase separation of organic explosives is coupled to a 16 min ion-exchange separation of anions present in inorganic explosives, providing a complete pre-blast analysis/identification system for the separation and detection of a complex mixture containing organic and/or inorganic explosive species. The total analysis time, including sufficient column re-equilibration between runs, was <25 min using the coupled system. By this method, the minimum resolution for the organic separation was 1.16 between nitroglycerin and tetryl and the detection limits ranged from 0.31 mg L(-1) for cyclotetramethylene tetranitramine (HMX) and 1.54 mg L(-1) for pentaerythrite tetranitrate (PETN), while the minimum resolution for the inorganic separation was 0.99 between azide and nitrate, and the detection limits ranged from 7.70 μg L(-1) for fluoride and 159.50 μg L(-1) for benzoate.
Discovery of Biomarkers for Tasmanian Devil Cancer (DFTD) by Metabolic Profiling of Serum
Publisher: American Chemical Society (ACS)
Date: 23-09-2016
DOI: 10.1021/ACS.JPROTEOME.6B00629
Abstract: Devil facial tumor disease (DFTD) is a transmissible cancer threatening Tasmanian devils (Sarcophilus harrisii) with extinction. There is no preclinical test available for DFTD, and thus our aim was to find biomarkers for DFTD by metabolic fingerprinting. Seventy serum s les from wild Tasmanian devils (35 controls, 35 with tumors) were analyzed by liquid chromatography-high-resolution mass spectrometry. Features were selected by multivariate models (PLS/DA, random forests) comparing age-matched training set (n = 20 × 2) and further complying with fold-change threshold (≥1.4) and Mann-Whitney U-tests with correction for multiple hypotheses (false discovery rate (FDR) q 0.45, p < 0.01). Additional potential markers included amino acid and lipid metabolites, while cortisol and urea were the most significant health predictors (AUC ≥ 0.90). PLS/DA resulted in AUC = 0.997 for the training set and overall sensitivity of 91% and specificity of 97%. A support vector machine model utilizing only the major peptide marker and seven other metabolites led to overall 94% sensitivity and specificity. The novel findings in this first DFTD metabolomics study shed light on metabolic changes in Tasmanian devils affected by DFTD and provide a valuable step toward the development of prognostic biomarkers.
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.
Identification of homemade inorganic explosives by ion chromatographic analysis of post-blast residues
Publisher: Elsevier BV
Date: 02-2008
DOI: 10.1016/J.CHROMA.2008.01.014
Abstract: Anions and cations of interest for the post-blast identification of homemade inorganic explosives were separated and detected by ion chromatographic (IC) methods. The ionic analytes used for identification of explosives in this study comprised 18 anions (acetate, benzoate, bromate, carbonate, chlorate, chloride, chlorite, chromate, cyanate, fluoride, formate, nitrate, nitrite, perchlorate, phosphate, sulfate, thiocyanate and thiosulfate) and 12 cations (ammonium, barium(II), calcium(II), chromium(III), ethylammonium, magnesium(II), manganese(II), methylammonium, potassium(I), sodium(I), strontium(II), and zinc(II)). Two IC separations are presented, using suppressed IC on a Dionex AS20 column with potassium hydroxide as eluent for anions, and non-suppressed IC for cations using a Dionex SCS 1 column with oxalic acid/acetonitrile as eluent. Conductivity detection was used in both cases. Detection limits for anions were in the range 2-27.4ppb, and for cations were in the range 13-115ppb. These methods allowed the explosive residue ions to be identified and separated from background ions likely to be present in the environment. Linearity (over a calibration range of 0.05-50ppm) was evaluated for both methods, with r(2) values ranging from 0.9889 to 1.000. Reproducibility over 10 consecutive injections of a 5ppm standard ranged from 0.01 to 0.22% relative standard deviation (RSD) for retention time and 0.29 to 2.16%RSD for peak area. The anion and cation separations were performed simultaneously by using two Dionex ICS-2000 chromatographs served by a single autoinjector. The efficacy of the developed methods was demonstrated by analysis of residue s les taken from witness plates and soils collected following the controlled detonation of a series of different inorganic homemade explosives. The results obtained were also confirmed by parallel analysis of the same s les by capillary electrophoresis (CE) with excellent agreement being obtained.
Probing the kinetic performance limits for ion chromatography. II. Gradient conditions for small ions
Publisher: Elsevier BV
Date: 07-2010
DOI: 10.1016/J.CHROMA.2010.05.002
Abstract: A gradient kinetic plot method is used for theoretical characterisation of the performance of polymeric particulate anion exchange columns for gradient separations of small inorganic anions. The method employed requires only information obtained from a series of isocratic column performance measurements and in silico predictions of retention time and peak width under gradient conditions. Results obtained under practically constrained conditions provide parameters for the generation of high peak capacities and rapid peak production for fast analysis to be determined. Using this prediction method, a maximum theoretical peak capacity of 84 could be used to achieve separation of 26 components using a 120min gradient (R(s)>1). This approach provides a highly convenient tool for development of both mono- and multidimensional ion chromatography (IC) methodologies as it yields comprehensive understanding of the influence of gradient slope, analysis time, column length and temperature upon kinetically optimised gradient performance.
Comment on ?Structural characterization of dissolved organic matter: a review of current techniques for isolation and analysis? by E. C. Minor, M. M. Swenson, B. M. Mattson, and A. R. Oyler, Environ. Sci.: Processes Impacts, 2014, 16, 2064
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4EM00631C
Abstract: This letter discusses the origins of certain components of dissolved organic matter.
Characterization of large surface area polymer monoliths and their utility for rapid, selective solid phase extraction for improved sample clean up
Publisher: Elsevier BV
Date: 09-2015
DOI: 10.1016/J.CHROMA.2015.07.065
Abstract: While polymer monoliths are widely described for solid phase extraction (SPE), appropriate characterization is rarely provided to unravel the links between physical characteristics and observed advantages and disadvantages. Two known approaches to fabricate large surface area polymer monoliths with a bimodal pore structure were investigated. The first incorporated a high percentage of inyl benzene (PDVB) and the second explored hypercrosslinking of pre-formed monoliths. Adsorption of probe analytes anisole, benzoic acid, cinnamic acid, ibuprofen and cortisone were investigated using frontal analysis and the SPE performance was compared with particulate adsorbents. Frontal analysis of anisole described maximum adsorption capacities of 164mgg(-1) and 298mgg(-1) for hypercrosslinked and PDVB adsorbents, respectively. The solvated state specific surface area was calculated to be 341 and 518m(2)g(-1) respectively. BET revealed a hypercrosslinked surface area of 817m(2)g(-1), 2.5 times greater than in the solvated state. The PDVB BET surface area was 531m(2)g(-1), similar to the solvated state. Micropores of 1nm provided the enhanced surface area for hypercrosslinked adsorbents. PDVB displayed a pore size distribution of 1-6nm. Frontal analysis demonstrated the micropores present size exclusion for the larger probes. Recovery of anisole was determined by SPE using 0.4 and 1.0mLmin(-1). Recovery for PDVB remained constant at 90%±0.103 regardless of the extraction flow rate suggesting extraction performance is independent of flow rate. A more efficient s le purification of saccharin in urine was yielded by PDVB due to selective permeation of the small pores.
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.
Towards high capacity latex-coated porous polymer monoliths as ion-exchange stationary phases
Publisher: Royal Society of Chemistry (RSC)
Date: 2006
DOI: 10.1039/B511398A
Abstract: The preparation of high capacity agglomerated monolithic ion-exchangers for capillary ion chromatography is described. Post-modification of reactive monoliths was investigated as an alternative to co-polymerisation of a suitable functional monomer with an overarching goal of increasing ion-exchange capacity. Direct sulfonation of poly styrene-co- inyl benzene monoliths using concentrated sulfuric acid or chlorosulfonic acid was unsuccessful even for monoliths containing as low as 8% crosslinker. In contrast, chemical transformation of reactive monoliths containing glycidyl methacrylate was used to increase the ion-exchange capacity by up to more than thirty-fold with ion exchange capacities of 14-29 microequiv g(-1) achieved. Three different reactions were considered, including reaction with 4-hydroxybenenesulfonic acid under basic conditions reaction with thiobenzoic acid followed by transformation to a reactive thiol and the subsequent oxidation to the sulfonic acid and direct sulfonation with sodium sulfite. Of these, the reaction with sodium sulfite resulted in the most significant increase in the capacity and the best separation performance. In the isocratic mode separation efficiencies of over 13,500 plates m(-1) were observed (for iodate). The separation of seven inorganic anions was also demonstrated using a hydroxide gradient.
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 (
Hop (Humulus lupulus L.) Volatiles Variation During Storage
Publisher: Informa UK Limited
Date: 26-02-2020
The antimicrobial efficacy of native Australian essential oils in liquid and vapour phase against foodborne pathogens and spoilage microorganisms
Publisher: Elsevier BV
Date: 09-2023
Longitudinal On-Column Thermal Modulation for Comprehensive Two-Dimensional Liquid Chromatography
Publisher: American Chemical Society (ACS)
Date: 22-12-2017
DOI: 10.1021/ACS.ANALCHEM.6B03279
Abstract: Longitudinal on-column thermal modulation for comprehensive two-dimensional liquid chromatography is introduced. Modulation optimization involved a systematic investigation of heat transfer, analyte retention, and migration velocity at a range of temperatures. Longitudinal on-column thermal modulation was realized using a set of alkylphenones and compared to a conventional valve-modulator employing s le loops. The thermal modulator showed a reduced modulation-induced pressure impact than valve modulation, resulting in reduced baseline perturbation by a factor of 6 yielding a 6-14-fold improvement in signal-to-noise. A red wine s le was analyzed to demonstrate the potential of the longitudinal on-column thermal modulator for separation of a complex s le. Discrete peaks in the second dimension using the thermal modulator were 30-55% narrower than with the valve modulator. The results shown herein demonstrate the benefits of an active focusing modulator, such as reduced detection limits and increased total peak capacity.
Enantioselective gas chromatographic analysis of monoterpenes in essential oils of the family Myrtaceae
Publisher: Wiley
Date: 2004
DOI: 10.1002/FFJ.1368
Simple, quantitative method for low molecular weight dissolved organic matter extracted from natural waters based upon high performance counter-current chromatography
Publisher: Elsevier BV
Date: 02-2016
DOI: 10.1016/J.ACA.2016.01.003
Abstract: A simple, high-performance counter-current chromatography method with sequential UV absorbance (254 nm) and evaporative light scattering detection (ELSD) was developed for the quantification of pre-extracted low molecular weight dissolved organic matter (DOM) extracted from natural waters. The method requires solid-phase extraction (SPE) extraction of only small volumes of water s les, here using poly(styrene inylbenzene)-based extraction cartridges (Varian PPL). The extracted and concentrated DOM was quantified using reversed-phase high-performance counter-current chromatography (HPCCC), with a water/methanol (5:5) mobile phase and hexane/ethyl acetate (3:7) stationary phase. The critical chromatographic parameters were optimised, applying a revolution speed of 1900 rpm and a flow-rate of 1 mL min(-1). Under these conditions, 50 μL of extracted DOM solution could be injected and quantified using calibration against a reference natural dissolved material (Suwannee River), based upon UV absorbance at 254 nm and ELSD detection. Both detection methods provided excellent linearity (R(2) > 0.995) for DOM across the concentration ranges of interest, with limits of detection of 4 μg ml(-1) and 7 μg ml(-1) for ELSD and UV absorbance, respectively. The method was validated for peak area precision ( 95% recovery). The developed method was applied to the determination of the concentration of DOM in seawater, based upon initial s le volumes as small as 20 mL.
Evaporative membrane modulation for comprehensive two-dimensional liquid chromatography
Publisher: Elsevier BV
Date: 02-2018
DOI: 10.1016/J.ACA.2017.11.053
Abstract: An evaporative membrane modulator was developed, built and evaluated to avoid loss of performance in the second dimension when coupling two-dimensional liquid chromatography systems. The automated interface reduces the volume after
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.
Unravelling the relationship between aroma compounds and consumer acceptance: Coffee as an example
Publisher: Wiley
Date: 07-07-2020
High temperature liquid chromatography of intact proteins using organic polymer monoliths and alternative solvent systems
Publisher: Elsevier BV
Date: 05-2010
DOI: 10.1016/J.CHROMA.2010.03.033
Abstract: Alternative approaches to conventional acetonitrile gradient methods for reversed-phase liquid chromatographic analysis of intact proteins have been investigated using commercial poly(styrene-co- inylbenzene) monolithic columns (Dionex ProSwift RP-2H and RP-4H). Alternative solvents to acetonitrile (2-propanol and methanol) coupled with elevated temperatures demonstrated complementary approaches to adjusting separation selectivity and reducing organic solvent consumption. Measurements of peak area at increasing isothermal temperature intervals indicated that only minor (<5%) decreases in detectable protein recovery occurred between 40 and 100 degrees C on the timescale of separation (2-5 min). The reduced viscosity of a 2-propanol/water eluent at elevated temperatures permitted coupling of three columns to increase peak production (peaks/min) by 16.5%. Finally, narrow-bore (1 mm i.d.) columns were found to provide a more suitable avenue to fast, high temperature (up to 140 degrees C) separations.
Temperature pulsing for controlling chromatographic resolution in capillary liquid chromatography
Publisher: American Chemical Society (ACS)
Date: 19-03-2012
DOI: 10.1021/AC300161B
Abstract: In this study we introduce the implementation of rapid temperature pulses for selectivity tuning in capillary liquid chromatography. Short temperature pulses improved resolution in discrete sections of chromatograms, demonstrated for ion-exchange chromatography (IC) and hydrophilic interaction chromatography (HILIC) modes. Using a resistively heated column module capable of accurate and rapid temperature changes, this concept is first illustrated with separations of small anions by IC using a packed capillary column as well as a series of nucleobases and nucleosides by HILIC using a silica monolithic column with zwitterionic functionality (ZIC-HILIC). Both positive (increasing temperature) and negative temperature pulses are demonstrated to produce significant changes in selectivity and are useful approaches for improving resolution between coeluted compounds. The approach was shown to be reproducible over a large number of replicates. Finally, the use of temperature gradients as well as other complex temperature profiles was also examined for both IC and HILIC separations.
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.
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.
Parallel comprehensive two-dimensional gas chromatography
Publisher: Elsevier BV
Date: 11-2017
DOI: 10.1016/J.CHROMA.2017.09.063
Abstract: We introduce an information rich analytical approach called parallel comprehensive two-dimensional gas chromatography (2GC×2GC). This parallel chromatography approach splits injected s les into two independent two-dimensional column ensembles and provides two GC×GC separations by using contra-directional thermal modulation. The first-dimension (
Evaluation of a miniaturised single-stage thermal modulator for comprehensive two-dimensional gas chromatography of petroleum contaminated soils
Publisher: Elsevier BV
Date: 09-2016
DOI: 10.1016/J.CHROMA.2016.08.009
Abstract: A novel miniaturised single-stage resistively heated thermal modulator was investigated as an alternative to cryogenic modulation for use in comprehensive two-dimensional gas chromatography (GC×GC). The single-stage thermal modulator described herein yielded average retention time relative standard deviations (RSD) of ≤0.2% RSD (first-dimension) and ≤3.4% RSD (second-dimension). The average peak widths generated by the modulator were 72±3ms, and the peak area precision was better than 5.3% RSD for a range of polar and non-polar test analytes. GC×GC analysis can be performed using this modulator without the requirement for cryogenic cooling or additional pressure control modules for flow modulation. The modulator and associated electronics are compact and amenable towards field analysis. The modulator was used for qualitative and quantitative characterisation of petroleum-contaminated soils derived from a sub-Antarctic research station at Macquarie Island. The limit of detection compared to standard 1D GC analysis was improved from 64 to 11mgkg(-1). An automated method of analysing and categorising s les using principal component analysis is presented.
Assessment of the complementarity of temperature and flow-rate for response normalisation of aerosol-based detectors
Publisher: Elsevier BV
Date: 08-2014
DOI: 10.1016/J.CHROMA.2014.06.055
Abstract: The solvent dependency of the detection response is a major limitation of corona-charged aerosol detection (C-CAD). The present study empirically investigates the utility of temperature and flow-rate gradients to overcome solvent gradient limitations of C-CAD. In preliminary flow-injection investigations, it is demonstrated that the response of C-CAD remains relatively unaltered with variations in flow-rate when used with water-rich eluents. Based on these findings two separation approaches were developed and their utility for C-CAD response normalisation was demonstrated using a mixture of eight analytes. In the first approach the use of a solvent gradient is replaced with a temperature gradient performed under isocratic mobile phase conditions. Detection response is further enhanced by mixing a secondary stream of pure acetonitrile with the column effluent, yielding a 3-fold increase in detection response. In the second approach, flow-rate programming is used to improve speed of isocratic-temperature gradient separation. The use of simultaneous variation in flow-rate and column temperature reduced the separation time by 30%, with relatively uniform analyte response. Lastly, an inverse-gradient solvent compensation approach was used to evaluate the response homogeneity and the applicability of the above approaches for quantitative analysis. Good peak area reproducibility (RSD% 0.994, on a log-scale) over the s le mass range of 0.1-10 μg was achieved. The response deviation across the mixture of eight compounds at seven concentration levels was 6-13% compared to 21-39% when a conventional solvent gradient was applied and this response deviation was comparable to that obtained in the inverse gradient solvent compensation approach. Finally, applicability of these approaches for typical pharmaceutical impurity profiling was demonstrated at a concentration of 5 μg/mL (0.1% of the principal compound).
Kinetic optimisation of open-tubular liquid-chromatography capillaries coated with thick porous layers for increased loadability
Publisher: Elsevier BV
Date: 11-2011
DOI: 10.1016/J.CHROMA.2011.09.047
Abstract: The kinetic optimisation of open-tubular liquid chromatography (OTLC) columns has been revisited by taking the thick-film effects for porous coatings on retention, column resistance, band broadening and mass loadability into account. Considering the most advantageous case (i.e. where the retentive layer allows for the same high internal diffusion coefficient as conventional porous particles), calculations show the need for the development of coating procedures leading to porous films filling up approximately 50-70% of the total column diameter. Furthermore, to achieve optimum kinetic performance for separations of small molecules with total analysis times of less than 8h (k'=9), total column diameters should be less than 6 μm with lengths typically greater than 0.8m for N values of 125,000-500,000 at a pressure of 400 bar. The use of elevated temperature LC (90°C) is also shown to increase the allowable total column diameter to up to 9 μm for a larger range of N values (100,000-880,000).
The Role of Potent Thiols in “Empyreumatic” Flint/Struck-Match/Mineral Odours in Chardonnay Wine
Publisher: Hindawi Limited
Date: 31-07-2023
DOI: 10.1155/2023/8847476
Abstract: Background and Aims. A wide range of Chardonnay styles exist on the market, from fruit-forward ex les to wines displaying “empyreumatic” aromas such as flint, smoky, mineral, and struck-match. The thiols 2-furylmethanethiol and phenylmethanethiol have been linked to these aromas, and this study aimed to determine the contribution of these compounds to specific sensory properties in Chardonnay wines, as well as the consumer acceptance of wine displaying “empyreumatic” aromas. Methods and Results. Twenty-four Australian and New Zealand Chardonnay wines were selected for volatile analysis and quantitative sensory descriptive analysis. Consumer liking of a subset of six wines was also determined, and a further sensory study involving additions of the thiols to a base wine was conducted. Partial least squares regression showed that flint/struck-match/mineral aromas were related to 2-furylmethanethiol concentration with phenylmethanethiol less well associated. The odorant addition study confirmed that 2-furylmethanethiol directed flint/struck-match/mineral aromas and exerted strong suppression of other aromas while phenylmethanethiol played a lesser role. Consumer acceptance (n = 92) was overall lower for wines displaying high flint/struck-match/mineral aromas, although cluster analysis of the liking scores identified a sizeable consumer group (33%) who preferred wines with this attribute. Conclusions. The potent thiol 2-furylmethanethiol was indicated to be the primary contributor to flint/struck-match/mineral aromas in Chardonnay wines, with phenylmethanethiol playing a subordinate role. Significance of the Study. Increased concentration of 2-furylmethanethiol and the conferred “empyreumatic” odours should be carefully considered when producing wine styles to appeal to consumers.
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
The effect of fat and coffee concentration on the consumer acceptance of iced‐coffee beverages
Publisher: Wiley
Date: 15-05-2022
Abstract: The fat content of a product has the potential to influence consumer liking via mouthfeel, taste, and aroma modification. This study aims to determine the effects of fat and coffee concentration on sensory attributes and consumer liking of iced‐coffee beverages. Nine iced‐coffee beverages were formulated: low fat–low coffee medium fat–low coffee high fat–low coffee low fat–medium coffee medium fat–medium coffee high fat–medium coffee low fat–high coffee medium fat–high coffee and high fat–high coffee. Fat content was adjusted using different concentrations of cream, and coffee using different concentrations of Nescafé Blend 43. Regular coffee consumers ( n = 231) rated their overall liking using a 9‐point hedonic scale and completed a ranked preference based on degree of liking of all s les. Consumers also rated liking for sensory attributes: appearance, aroma, sweetness, coffee intensity, mouthfeel, and aftertaste. There were significant relationships between 1/ fat and 2/ coffee and liking of iced‐coffee beverages ( p 0.001). There were three clusters of consumers based on iced‐coffee preferences. Response surface curve indicated that overall liking of iced‐coffee beverages increased with the increase of fat and coffee concentration to a certain level, then continuing to increase the fat and coffee concentration decreases overall liking. The finding of this study provides valuable information on how fat and coffee concentrations can be adjusted to modify consumer acceptance of iced‐coffee beverages. The results of this research could be applied to reformulate iced‐coffee beverages, while ensuring consumer acceptance. In addition, this research provides evidence that sweetness, aftertaste, coffee‐intensity, and mouthfeel are important sensory attributes associated with consumer liking of iced‐coffee beverages.
Chromatographic methods for the isolation, separation and characterisation of dissolved organic matter
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5EM00223K
Abstract: This review presents an overview of the separation techniques applied to the complex challenge of dissolved organic matter characterisation.
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
Online Comprehensive Two-Dimensional Ion Chromatography × Capillary Electrophoresis
Publisher: American Chemical Society (ACS)
Date: 17-08-2015
DOI: 10.1021/ACS.ANALCHEM.5B01130
Abstract: A comprehensively coupled online two-dimensional ion chromatography-capillary electrophoresis (IC × CE) system for quantitative analysis of inorganic anions and organic acids in water is introduced. The system employs an in-house built sequential injection-capillary electrophoresis instrument and a nonfocusing modulation interface comprising a tee-piece and a six-port two-position injection valve that allows comprehensive s ling of the IC effluent. High field strength (+2 kV/cm) enables rapid second-dimension separations in which each peak eluted from the first-dimension separation column is analyzed at least three times in the second dimension. The IC × CE approach has been successfully used to resolve a suite of haloacetic acids, dalapon, and common inorganic anions. Two-dimensional peak capacity for IC × CE was 498 with a peak production rate of 9 peaks/min. Linear calibration curves were obtained for all analytes from 5 to 225 ng/mL (except dibromoacetic acid (10-225 ng/mL) and tribromoacetic acid (25-225 ng/mL)). The developed approach was used to analyze a spiked tap water s le, with good measured recoveries (69-119%).
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
Consumer Acceptance of Brown and White Rice Varieties
Publisher: MDPI AG
Date: 22-08-2021
Abstract: Rice is consumed as a staple food by more than half of the world’s population. Due to a higher fibre and micronutrient content, brown rice is more nutritious than white rice, but the consumption of brown rice is significantly lower than that of white rice, primarily due to sensory attributes. Therefore, the present research aimed to identify the sensory attributes which drive liking of Australian-grown brown and white rice varieties. Participants (n = 139) tasted and scored (9-point hedonic scale) their liking (i.e., overall liking, aroma, colour and texture) of brown and white rice types of Jasmine (Kyeema), Low GI (Doongara), and Medium grain rice (Amaroo). In addition, participants scored aroma, colour, hardness, fluffiness, stickiness, and chewiness, on Just About Right Scales. A within-subjects crossover design with randomised order (William’s Latin Square design) was used with six repeated s les for liking and Just About Right scales. Penalty analyses were applied to determine the relative influence of perception of sensory attributes on consumer liking of the rice varieties. Across all varieties, white rice was liked more than brown rice due to the texture and colour, and Jasmine rice was preferred over Low GI and Medium Grain. Rice texture (hardness and chewiness) was the most important sensory attribute among all rice varieties and aroma was important for driving of liking between white rice varieties.
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.
Applications of resistive heating in gas chromatography: A review
Publisher: Elsevier BV
Date: 11-2013
DOI: 10.1016/J.ACA.2013.04.063
Abstract: Gas chromatography is widely applied to separate, identify, and quantify components of s les in a timely manner. Increasing demand for analytical throughput, instrument portability, environmental sustainability, and more economical analysis necessitates the development of new gas chromatography instrumentation. The applications of resistive column heating technologies have been espoused for nearly thirty years and resistively heated gas chromatography has been commercially available for the last ten years. Despite this lengthy period of existence, resistively heated gas chromatography has not been universally adopted. This low rate of adoption may be partially ascribed to the saturation of the market with older convection oven technology, coupled with other analytical challenges such as s ling, injection, detection and data processing occupying research. This article assesses the advantages and applications of resistive heating in gas chromatography and discusses practical considerations associated with adoption of this technology.
Probing the kinetic performance limits for ion chromatography. I. Isocratic conditions for small ions
Publisher: Elsevier BV
Date: 07-2010
DOI: 10.1016/J.CHROMA.2010.05.066
Abstract: The first use of the kinetic plot method to characterise the performance of ion-exchange columns for separations of small inorganic anions is reported. The influence of analyte type (mono- and alent), particle size (5 and 9microm), temperature (30 and 60 degrees C) and maximum pressure drop upon theoretical extrapolations was investigated using data collected from anion-exchange polymeric particulate columns. The quality of extrapolations was found to depend upon the choice of analyte, but could be verified by coupling a series of columns to demonstrate some practical solutions for ion chromatography separations requiring relatively high efficiency. Separations of small anions yielding 25-40,000 theoretical plates using five serially connected columns (9microm particles) were obtained and yielded deviations of <15% from the kinetic plot predictions. While this approach for achieving high efficiencies results in a very long analysis time (t(0)=21min), separations yielding approximately 10,000 theoretical plates using two serially connected columns (t(0) 10min).
Gas Chromatography
Publisher: Elsevier
Date: 2013
Fast ion chromatography using short anion exchange columns
Publisher: Elsevier BV
Date: 11-2009
DOI: 10.1016/J.CHROMA.2009.10.003
Abstract: A fast ion chromatographic system is described which uses shorter column lengths and compares various eluent profiles in order to maximise the performance without sacrificing the chromatographic resolution. Both isocratic and gradient elution profiles were considered to find the most efficient mode of separation. The separation and determination of seven target anions (chloride, chlorate, nitrate, chromate, sulfate, thiocyanate and perchlorate) was achieved using a short (4mm ID, 50mm long) column packed with Dionex AS20 high-capacity anion exchange material. A hydroxide eluent was used at an initial concentration of 25 mM (at a flow-rate of 1.0 mL/min) and two performance maxima were found. The maximum efficiency occurred at a normalised gradient r rate of 5mM/t(0), resulting in a peak capacity of 16, while the fastest separation (<3 min) occurred at a normalised r rate of 30 mM/t(0). The retention time, peak width and resolution using the different eluent profiles on varying column lengths is also compared. Further investigations in this study determined that the highest peak capacity separation under gradient conditions could be approximated using an isocratic separation. The advantage of using this novel approach to approximate the maximum efficiency separation removes the need for column re-equilibration that is required for gradient elution resulting in faster analyses and enhanced s le throughput, with benefits in particular for multidimensional chromatography.
Back-flushing and heart cut capillary gas chromatography using planar microfluidic Deans’ switching for the separation of benzene and alkylbenzenes in industrial samples
Publisher: Elsevier BV
Date: 11-2015
DOI: 10.1016/J.CHROMA.2015.10.027
Abstract: Planar microfluidic devices coupled with modern electronic pressure control have allowed gas chromatography (GC) practitioners to easily manipulate chromatographic systems to achieve heart cut and back-flushing configurations. These planar microfluidic devices have enhanced the connectivity between different components of GC instrumentation and have improved the inertness and minimised system dead volumes compared to classical chromatographic unions and valves. In the present contribution the setup and configuration of two multidimensional GC (MDGC) platforms is described for achieving the separation and quantification of trace level target C6-C8 alkylbenzenes in styrene monomer and Isoparaffin™ solvents, using flame ionisation detection (FID). The performance of these MDGC platforms indicated excellent retention time (0.2% relative standard deviation, RSD) and peak area repeatability (1% RSD) for all analytes of interest. The limit of detection (LOD) was 0.8 mg kg(-1) for benzene in styrene monomer, and 2.4-2.8 mg kg(-1) for C6-C8 alkylbenzenes such as benzene, toluene, ethylbenzene and xylene in Isoparaffin™ solvent.
A simplified approach to direct SPE‐MS
Publisher: Wiley
Date: 09-2012
Abstract: Microextraction by packed sorbent (MEPS) has been directly hyphenated with ESI-MS for the rapid screening of opiates and codeine metabolites in urine. This study introduces a novel format of MEPS that incorporates a two-way valve in the barrel of the syringe enabling the direction of liquid flow to be manipulated. Controlled directional flow (CDF) MEPS allows sharp, concentrated s le bands to be delivered directly to the MS in small volumes and effectively eliminates the need to optimize elution. The method optimization assessed the recovery, matrix effects, and the speed of infusion, all critical variables for optimum ESI performance. Matching extraction workflows demonstrated a reduction in carryover from 65% for conventional MEPS to only 1% for CDF MEPS. The recovery (<89% for 50 μL s le), matrix effects ( 0.99), and LODs (<5 ng/mL) were determined to demonstrate method performance. The optimized approach was employed for the screening of codeine metabolites in urine. The ion trace revealed sharp s le bands corresponding to the codeine metabolites. At-line MEPS-ESI-MS allowed both s le preparation and analysis to be completed in only 5 min facilitating high throughput and alleviating the burden of method development.
On-line solvent exchange system: Automation from extraction to analysis
Publisher: Elsevier BV
Date: 2019
DOI: 10.1016/J.ACA.2018.09.044
Abstract: Removal of organic solvent from s le extracts is required before analysis by reversed phase HPLC to preserve chromatographic performance and allow for bigger injection volumes, boosting sensitivity. Herein, an automated on-line extraction evaporation procedure is integrated with HPLC analysis. The evaporation occurs inside a 200 μm microfluidic channel confined by a vapor permeable membrane. A feedback control algorithm regulates evaporation rate keeping the output flow rate constant. The evaporation process across this membrane was firstly characterized with water/solvent mixtures showing organic solvent removal capabilities. This system allowed continuous methanol, ethanol and acetonitrile removal from s les containing up to 80% organic solvent. An evaporative injection procedure was developed demonstrating the use of the device for fully integrated extract reconstitution coupled to HPLC analysis, applied to analysis of the antibiotic chlor henicol in milk s les. S le reconstitution and collection was performed in less than 10 min and can be executed simultaneously to HPLC analysis of the previous s le in a routine workflow, thus having minimal impact on the total s le analysis time when run in a sequence.
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
Porous, High Capacity Coatings for Solid Phase Microextraction by Sputtering
Publisher: American Chemical Society (ACS)
Date: 19-01-2016
DOI: 10.1021/ACS.ANALCHEM.5B03181
Abstract: We describe a new process for preparing porous solid phase microextraction (SPME) coatings by the sputtering of silicon onto silica fibers. The microstructure of these coatings is a function of the substrate geometry and mean free path of the silicon atoms, and the coating thickness is controlled by the sputtering time. Sputtered silicon structures on silica fibers were treated with piranha solution (a mixture of concd H2SO4 and 30% H2O2) to increase the concentration of silanol groups on their surfaces, and the nanostructures were silanized with octadecyldimethylmethoxysilane in the gas phase. The attachment of this hydrophobic ligand was confirmed by X-ray photoelectron spectroscopy and contact angle goniometry on model, planar silicon substrates. Sputtered silicon coatings adhered strongly to their surfaces, as they were able to pass the Scotch tape adhesion test. The extraction time and temperature for headspace extraction of mixtures of alkanes and alcohols on the sputtered fibers were optimized (5 min and 40 °C), and the extraction performances of SPME fibers with 1.0 or 2.0 μm of sputtered silicon were compared to those from a commercial 7 μm poly(dimethylsiloxane) (PDMS) fiber. For mixtures of alcohols, aldehydes, amines, and esters, the 2.0 μm sputtered silicon fiber yielded signals that were 3-9, 3-5, 2.5-4.5, and 1.5-2 times higher, respectively, than those of the commercial fiber. For the heavier alkanes (undecane-hexadecane), the 2.0 μm sputtered fiber yielded signals that were approximately 1.0-1.5 times higher than the commercial fiber. The sputtered fibers extracted low molecular weight analytes that were not detectable with the commercial fiber. The selectivity of the sputtered fibers appears to favor analytes that have both a hydrophobic component and hydrogen-bonding capabilities. No detectable carryover between runs was noted for the sputtered fibers. The repeatability (RSD%) for a fiber (n = 3) was less than 10% for all analytes tested, and the between-fiber reproducibility (n = 3) was 0-15%, generally 5-10%, for all analytes tested. The repeatabilities of our sputtered fibers and the commercial 7 μm PDMS fiber are essentially the same. Fibers could be used for at least 300 extractions without loss of performance. More than 50 compounds were identified in a gas chromatography-mass spectrometry headspace analysis of a real world botanical s le with the 2.0 μm fiber.
Identification of inorganic improvised explosive devices using sequential injection capillary electrophoresis and contactless conductivity detection
Publisher: American Chemical Society (ACS)
Date: 10-11-2011
DOI: 10.1021/AC2020195
Abstract: A simple sequential injection capillary electrophoresis (SI-CE) instrument with capacitively coupled contactless conductivity detection (C(4)D) has been developed for the rapid separation of anions relevant to the identification of inorganic improvised explosive devices (IEDs). Four of the most common explosive tracer ions, nitrate, perchlorate, chlorate, and azide, and the most common background ions, chloride, sulfate, thiocyanate, fluoride, phosphate, and carbonate, were chosen for investigation. Using a separation electrolyte comprising 50 mM tris(hydroxymethyl)aminomethane, 50 mM cyclohexyl-2-aminoethanesulfonic acid, pH 8.9 and 0.05% poly(ethyleneimine) (PEI) in a hexadimethrine bromide (HDMB)-coated capillary it was possible to partially separate all 10 ions within 90 s. The combination of two cationic polymer additives (PEI and HDMB) was necessary to achieve adequate selectivity with a sufficiently stable electroosmotic flow (EOF), which was not possible with only one polymer. Careful optimization of variables affecting the speed of separation and injection timing allowed a further reduction of separation time to 55 s while maintaining adequate efficiency and resolution. Software control makes high s le throughput possible (60 s les/h), with very high repeatability of migration times [0.63-2.07% relative standard deviation (RSD) for 240 injections]. The separation speed does not compromise sensitivity, with limits of detection ranging from 23 to 50 μg·L(-1) for all the explosive residues considered, which is 10× lower than those achieved by indirect absorbance detection and 2× lower than those achieved by C(4)D using portable benchtop instrumentation. The combination of automation, high s le throughput, high confidence of peak identification, and low limits of detection makes this methodology ideal for the rapid identification of inorganic IED residues.
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.
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
Packing procedures for high efficiency, short ion-exchange columns for rapid separation of inorganic anions
Publisher: Elsevier BV
Date: 10-2008
DOI: 10.1016/J.CHROMA.2008.08.056
Abstract: An optimised packing procedure for the production of high efficiency, short, particle-packed ion-exchange columns is reported. Slurry-packing techniques were applied to a series of interconnected short columns, with the columns situated intermediate between the inlet and outlet ends of the series being used for separations. The fast separation and determination of inorganic anions was achieved using short (4mm ID, 30mm long) columns packed with Dionex AS20 high-capacity anion-exchange stationary phase. Seven inorganic anions (bromate, chloride, chlorate, nitrate, sulfate, chromate and perchlorate) are separated in 2.6min using a hydroxide gradient and a flow-rate of 1.8mL/min (total analysis time including re-equilibration was 3.5min). Under isocratic conditions, the home-packed columns exhibited efficiency values of 43,000N/m for chloride at a flow-rate of 0.3mL/min, compared to 54,000N/m for a commercial 250mm AS20 column at the same flow-rate. However, the short columns gave approximately a threefold higher s le throughput. The short, home-packed columns could be produced reproducibly and gave consistent performance over extended periods of usage.
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.
Multiplexed dual first-dimension comprehensive two-dimensional gas chromatography–mass spectrometry with contra-directional thermal modulation
Publisher: Elsevier BV
Date: 10-2014
DOI: 10.1016/J.CHROMA.2014.09.014
Abstract: A multiplexed dual-primary column comprehensive two-dimensional gas chromatography-mass spectrometry approach (2GC×GC-MS) is introduced. The approach splits injected s les into two first-dimension columns with different stationary phases, and recombines the two streams into one second-dimension column that terminates at a single detector. The approach produces two two-dimensional chromatograms for each injection, and is made possible by using a dual-stage modulator operated in contra-directional modulation mode. The dual two-dimensional chromatograms produced by this single detector system provide complementary information due to selectivity differences between the three separation columns used in the column ensemble. An aged Australian tea tree (Melaleuca alternifolia) essential oil was analyzed to demonstrate the 2GC×GC-MS approach. The number of compounds separated by each of the GC×GC separations in the 2GC×GC experiment is comparable to conventional GC×GC experiments with matching column configurations. Robust peak assignment was possible for this s le based on the combination of MS library matches and multiple linear retention index searching. Forty-nine components (22 unique) were identified using a non-polar×mid-polar column combination and 34 components (7 unique) were positively identified using a polar×mid-polar column combination. Twenty-seven peak assignments were corroborated by positive identification in both of the multiplexed separations.
Real-Time Mass Spectrometry Monitoring of Oak Wood Toasting: Elucidating Aroma Development Relevant to Oak-aged Wine Quality
Publisher: Springer Science and Business Media LLC
Date: 27-11-2015
DOI: 10.1038/SREP17334
Abstract: We introduce a real-time method to monitor the evolution of oak aromas during the oak toasting process. French and American oak wood boards were toasted in an oven at three different temperatures, while the process-gas was continuously transferred to the inlet of a proton-transfer-reaction time-of-flight mass spectrometer for online monitoring. Oak wood aroma compounds important for their sensory contribution to oak-aged wine were tentatively identified based on soft ionization and molecular mass. The time-intensity profiles revealed toasting process dynamics illustrating in real-time how different compounds evolve from the oak wood during toasting. Sufficient sensitivity was achieved to observe spikes in volatile concentrations related to cracking phenomena on the oak wood surface. The polysaccharide-derived compounds exhibited similar profiles whilst for lignin-derived compounds eugenol formation differed from that of vanillin and guaiacol at lower toasting temperatures. Significant generation of oak lactone from precursors was evident at 225 o C. Statistical processing of the real-time aroma data showed similarities and differences between in idual oak boards and oak wood sourced from the different origins. This study enriches our understanding of the oak toasting process and demonstrates a new analytical approach for research on wood volatiles.
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.
Kinetic performance optimisation for liquid chromatography: Principles and practice
Publisher: Wiley
Date: 10-03-2011
Abstract: This HPLC tutorial focuses on the preparation and use of kinetic plots to characterise the performance in isocratic and gradient LC. This graphical approach allows the selection of columns (i.e. optimum particle size and column length) and LC conditions (operating pressure and temperature) to generate a specific number of plates or peak capacity in the shortest possible analysis time. Instrument aspects including the influence of extra-column effects (maximum allowable system volume) and thermal operating conditions (oven type) on performance are discussed. In addition, the performance characteristics of porous-shell particle-packed columns and monolithic stationary phases are presented and the potential of future column designs is discussed.
Poly(ethylene glycol) functionalization of monolithic poly(divinyl benzene) for improved miniaturized solid phase extraction of protein-rich samples
Publisher: Springer Science and Business Media LLC
Date: 11-01-2017
DOI: 10.1007/S00216-016-0164-Y
Abstract: Non-specific protein adsorption on hydrophobic solid phase extraction (SPE) adsorbents can reduce the efficacy of purification. To improve s le clean-up, poly( inyl benzene) (PDVB) monoliths grafted with hydrophilic polyethylene glycol methacrylate (PEGMA) were developed. Residual vinyl groups (RVGs) of the PDVB were employed as anchor points for PEGMA grafting. Two PEGMA monomers, M
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.
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.
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.
Identifying aroma‐active compounds in coffee‐flavored dairy beverages
Publisher: Wiley
Date: 17-02-2022
Abstract: Coffee aroma is a complex mixture of volatile compounds. This study characterized the important aroma‐active compounds associated with consumer liking in formulated coffee‐flavored dairy beverages. Nine coffee‐flavored dairy beverages were formulated: low fat–low coffee medium fat–low coffee high fat–low coffee low fat–medium coffee medium fat–medium coffee high fat–medium coffee low fat–high coffee medium fat–high coffee and high fat–high coffee. Regular coffee consumers, ( n = 231) used a nine‐point hedonic scale to rate acceptance of aroma. Volatile compounds were extracted by head space‐solid phase micro‐extraction (HS‐SPME) and analyzed by gas chromatography‐mass spectrometry‐olfactometry (GC‐MS‐O) using a modified frequency (MF) approach. Fifty‐two aroma‐active compounds were detected. Thirty‐one aroma‐active compounds were considered important compounds with MF‐value ≥ 50%. The total number of aroma‐active compounds and their intensity were affected because of fat and coffee concentration. Partial least squares regression (PLSR) was performed to determine the relationship between aroma‐active compounds and liking. PLSR analysis identified three groups of compounds regarding liking. Twenty‐five compounds were associated with positive liking, for ex le, 2‐(methylsulfanylmethyl) furan (coffee like). Sixteen compounds were negatively associated with liking, for ex le, 2‐methoxyphenol (bacon, medicine like). Eleven detected compounds had no association with liking, for ex le, butane‐2,3‐dione (butter, fruit like). Practical Application : The result of this study may be applied to formulate coffee‐flavored dairy beverages to maximize consumer acceptance and aroma‐liking. This study suggested too low coffee concentration is not desirable. Too much fat affects aroma release and/or alters the characteristic coffee flavor which negatively affects consumer acceptance.
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.
Kinetic performance appraisal of poly(styrene-co-divinylbenzene) monolithic high-performance liquid chromatography columns for biomolecule analysis
Publisher: Elsevier BV
Date: 06-2010
DOI: 10.1016/J.CHROMA.2010.04.007
Abstract: A broad appraisal of the kinetic performance of organic polymeric monolithic columns is reported using commercially available poly(styrene-co- inylbenzene) monolithic columns (Dionex ProSwift RP-1S). Analysis of a protein digest s le at elevated temperatures (> or =80 degrees C) indicated no apparent analyte degradation using an inert polymeric stationary phase. Comparison between low molecular weight solute and peptide separations highlighted the markedly different mass transport processes observed on macroporous monolithic beds and an improved C term at elevated temperature in both instances. The current usefulness of this column format for biomolecule analysis was further studied via employment of a kinetic performance characterisation for the first time to provide direction for column development servicing this application.
High temperature liquid chromatography with monolithic capillary columns and pure water eluent
Publisher: Royal Society of Chemistry (RSC)
Date: 2009
DOI: 10.1039/B815886J
Abstract: Use of an organic polymeric monolithic stationary phase for high temperature liquid chromatography (HTLC) with a pure water eluent is demonstrated for the first time. Separations of n-alcohols at temperatures exceeding 200 degrees C were achieved with no statistically significant reduction in chromatographic performance evident after continuous operation for 1000 column volumes above 200 degrees C.
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