Michael Breadmore

Microfluidic culture platform for studying neuronal response to mild to very mild axonal stretch injury

Publisher: AIP Publishing

Date: 07-2014

DOI: 10.1063/1.4891098

Abstract: A new model for studying localised axonal stretch injury is presented, using a microfluidic device to selectively culture axons on a thin, flexible poly (dimethylsiloxane) membrane which can be deflected upward to stretch the axons. A very mild (0.5% strain) or mild stretch injury (5% strain) was applied to primary cortical neurons after 7 days growth in vitro. The extent of distal degeneration was quantified using the degenerative index (DI, the ratio of fragmented axon area to total axon area) of axons fixed at 24 h and 72 h post injury (PI), and immunolabelled for the axon specific, microtubule associated protein-tau. At 24 h PI following very mild injuries (0.5%), the majority of the axons remained intact and healthy with no significant difference in DI when compared to the control, but at 72 h PI, the DI increased significantly (DI = 0.11 ± 0.03). Remarkably, dendritic beading in the somal compartment was observed at 24 h PI, indicative of dying back degeneration. When the injury level was increased (5% stretch, mild injury), microtubule fragmentation along the injured axons was observed, with a significant increase in DI at 24 h PI (DI = 0.17 ± 0.02) and 72 h PI (DI = 0.18 ± 0.01), relative to uninjured axons. The responses observed for both mild and very mild injuries are similar to those observed in the in vivo models of traumatic brain injury, suggesting that this model can be used to study neuronal trauma and will provide new insights into the cellular and molecular alterations characterizing the neuronal response to discrete axonal injury.

Extraction and on-line concentration of flavonoids in Brassica oleracea by capillary electrophoresis using large volume sample stacking

Publisher: Elsevier BV

Date: 07-2012

DOI: 10.1016/J.FOODCHEM.2012.01.006

On-capillary ion-exchange preconcentration of inorganic anions using open-tubular capillaries followed by elution with a transient isotachophoretic gradient

Publisher: Royal Society of Chemistry (RSC)

Date: 2000

DOI: 10.1039/B001836H

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2010-2012)

Publisher: Wiley

Date: 2013

DOI: 10.1002/ELPS.201200396

Abstract: CE has been alive for over two decades now, yet its sensitivity is still regarded as being inferior to that of more traditional methods of separation such as HPLC. As such, it is unsurprising that overcoming this issue still generates much scientific interest. This review continues to update this series of reviews, first published in Electrophoresis in 2007, with updates published in 2009 and 2011 and covers material published through to June 2012. It includes developments in the field of stacking, covering all methods from field lified s le stacking and large volume s le stacking, through to isotachophoresis, dynamic pH junction and sweeping. Attention is also given to online or inline extraction methods that have been used for electrophoresis.

3D Printed Micrometer-Scale Polymer Mounts for Single Crystal Analysis

Publisher: American Chemical Society (ACS)

Date: 30-03-2017

DOI: 10.1021/ACS.ANALCHEM.7B00443

Abstract: 3D printed micrometer-scale polymer mounts for single crystal analysis have been prepared by photopolymerization using digital light projection stereolithography (DLP-SLA), with a commercially available digital light projection stereolithography printer (US$4000) and 3DM-ABS resin (US$150 per liter). The polymer mounts were prepared in batches of 49 in 1 h 15 min, which allowed for rapid prototyping and testing of new crystal mounting designs, with a resin cost of 0.2¢ US per mount. The suitability of the 3D printed mounts for single crystal crystallography has been demonstrated through their use in Cu Kα X-ray diffraction experiments of Rochelle salt (sodium potassium tartrate), the protein lysozyme, and has been employed for routine crystallographic analysis of organic and inorganic materials.

High-Resolution Computer Simulations of Stacking of Weak Bases Using a Transient pH Boundary in Capillary Electrophoresis. 1. Concept and Impact of Sample Ionic Strength

Publisher: American Chemical Society (ACS)

Date: 08-12-2005

DOI: 10.1021/AC051420F

Abstract: The dynamics of focusing weak bases using a transient pH boundary was examined via high-resolution computer simulation software. Emphasis was placed on the mechanism and impact that the presence of salt, namely, NaCl, has on the ability to focus weak bases. A series of weak bases with mobilities ranging from 5 x 10(-9) to 30 x 10(-9) m2/V x s and pKa values between 3.0 and 7.5 were examined using a combination of 65.6 mM formic acid, pH 2.85, for the separation electrolyte, and 65.6 mM formic acid, pH 8.60, for the s le matrix. Simulation data show that it is possible to focus weak bases with a pKa value similar to that of the separation electrolyte, but it is restricted to weak bases having an electrophoretic mobility of 20 x 10(-9) m2/V x s or quicker. This mobility range can be extended by the addition of NaCl, with 50 mM NaCl allowing stacking of weak bases down to a mobility of 15 x 10(-9) m2/V x s and 100 mM extending the range to 10 x 10(-9) m2/V x s. The addition of NaCl does not adversely influence focusing of more mobile bases, but does prolong the existence of the transient pH boundary. This allows analytes to migrate extensively through the capillary as a single focused band around the transient pH boundary until the boundary is dissipated. This reduces the length of capillary that is available for separation and, in extreme cases, causes multiple analytes to be detected as a single highly efficient peak.

In‐Transit Electroextraction of Small‐Molecule Pharmaceuticals from Blood

Publisher: Wiley

Date: 12-02-2019

DOI: 10.1002/ANGE.201812077

Nanoporous Membranes for Microfluidic Concentration Prior to Electrophoretic Separation of Proteins in Urine

Publisher: American Chemical Society (ACS)

Date: 25-07-2016

DOI: 10.1021/ACS.ANALCHEM.6B02096

Abstract: A microfluidic device with two nanoporous membranes was developed to seamlessly integrate s le preparation and electrophoretic separation of proteins. The device was fabricated by sandwiching two nanoporous polycarbonate track etched (PCTE) membranes with differently sized nanopores between PDMS slabs containing embedded microchannels. The first membrane contained larger (100 nm) pores and served as an initial filter to screen out particles, cells and larger proteins. The second membrane contained smaller pores (10 nm) which facilitated transport of inorganic ions and small organic molecules, but not proteins. The sequential combination of these two membranes allows proteins to be concentrated and purified simultaneously. The device was used for the s le-in/answer-out quantification of albumin in human urine within 2.5 min with an improvement in sensitivity of 500 fold compared to a normal pinched injection using fluorescence detection. The linear range of was 0-100 μg mL(-1), with a LOD of 1.5 μg mL(-1) covering the diagnostic level of microalbuminuria of 30 μg mL(-1). The presented device, which is simple to make and use, provides a quantitative alternative for point-of-care detection of proteins, as demonstrated through its application to albumin in urine for the diagnoisis of (micro)albuminuria.

Acid‐induced transient isotachophoretic stacking of basic drugs in co‐electroosmotic flow capillary zone electrophoresis

Publisher: Wiley

Date: 28-11-2011

DOI: 10.1002/JSSC.201100788

Abstract: Online s le concentration or stacking of basic drugs by transient isotachophoresis with the injection of an acid in co-electroosmotic flow capillary zone electrophoresis was studied experimentally and with computer simulation. The acid stacking strategy afforded an order of magnitude improvement in concentration sensitivity for model tricyclic antidepressant and β blocker drugs.

On-line sequential injection-capillary electrophoresis for near-real-time monitoring of extracellular lactate in cell culture flasks

Publisher: Elsevier BV

Date: 2014

DOI: 10.1016/J.CHROMA.2013.11.006

Abstract: Cell culture has replaced many in vivo studies because of ethical and regulatory measures as well as the possibility of increased throughput. Analytical assays to determine (bio)chemical changes are often based on end-point measurements rather than on a series of sequential determinations. The purpose of this work is to develop an analytical system for monitoring cell culture based on sequential injection-capillary electrophoresis (SI-CE) with capacitively coupled contactless conductivity detection (C(4)D). The system was applied for monitoring lactate production, an important metabolic indicator, during mammalian cell culture. Using a background electrolyte consisting of 25mM tris(hydroxymethyl)aminomethane, 35mM cyclohexyl-2-aminoethanesulfonic acid with 0.02% poly(ethyleneimine) (PEI) at pH 8.65 and a multilayer polymer coated capillary, lactate could be resolved from other compounds present in media with relative standard deviations 0.07% for intraday electrophoretic mobility and an analysis time of less than 10min. Using the human embryonic kidney cell line HEK293, lactate concentrations in the cell culture medium were measured every 20min over 3 days, requiring only 8.73μL of s le per run. Combining simplicity, portability, automation, high s le throughput, low limits of detection, low s le consumption and the ability to up- and outscale, this new methodology represents a promising technique for near real-time monitoring of chemical changes in erse cell culture applications.

High intensity light emitting diode array as an alternative exposure source for the fabrication of electrophoretic microfluidic devices

Publisher: Elsevier BV

Date: 12-2008

DOI: 10.1016/J.CHROMA.2008.09.094

Abstract: A commercially available array of light emitting diodes (LEDs), namely a UV Shark series LED high flux array, was evaluated as a light source for photolithographic patterning of SU-8 photoresist for the fabrication of templates suitable to make poly(dimethylsiloxane) (PDMS) microchips for electrophoresis. At a distance of 15 cm from the substrate, a relatively even intensity of 0.76+/-0.05 mW/cm(2) was obtained over an area sufficient for patterning a 10 cm (4 in.) silicon wafer. The exposure source was evaluated using a spiral mask design covering a 10 cm wafer. PDMS replicates of this template made in a 25 microm thick layer of SU-8 3025 showed little variation in width over the surface of the substrate, with a variation of 3.2% RSD (n=36) and a maximum range in widths of 7.8% of the mean channel width. The use of the optional metal reflector available with the LED array provided partial collimation of the light allowing near vertical structures to be produced across the entire wafer, something which was not possible without the reflector. SU-8 masters prepared using the LED array were compared to masters made using an alternative cheap lithographic source, namely a gel crosslinker. The SU-8 features were much narrower with the LED array than the crosslinker due to the multiple light sources in the crosslinker. A PDMS microchip made using a SU-8 template created using the Shark UV LED array was used for the electrophoretic separation of three anionic fluorescent dyes, with efficiencies up to 32,000 plates. Given that the LED array can be purchased and assembled for less than US$ 500, the Shark UV LED array is a promising alternative to more expensive lithographic light sources and will have significant appeal to many researchers wishing to undertake research in microfluidics around the world.

On-capillary ion-exchange preconcentration of inorganic anions in open-tubular capillary electrochromatography with elution using transient-isotachophoretic gradients. 2. Characterization of the isotachophoretic gradient

Publisher: American Chemical Society (ACS)

Date: 12-01-2001

DOI: 10.1021/AC0010577

Abstract: Diffuse transient-isotachophoretic boundaries can be used as an elution gradient of increasing eluotropic strength to elute inorganic anions that have been preconcentrated on an open-tubular ion-exchange stationary phase prior to electrophoretic separation. The generation and characteristics of these gradients for elution after preconcentration have been investigated. The gradients are generated by placing a low-mobility, weak ion-exchange competing anion in the capillary (weak electrolyte, WE), and a high-mobility, strong ion-exchange competing anion in the electrolyte vials (strong electrolyte, SE). Application of voltage establishes a diffuse boundary with the composition changing from the weak anion to the strong anion. Comparison of elution gradients generated with different electrolyte systems was accomplished by comparing the eluotropic strength (a function of eluent concentration, ion-exchange selectivity coefficient, and charge) and the shape of the profile as it changes from WE to SE. The ion-exchange selectivity coefficient of the SE competing anion is important in establishing a sharp change in elution strength. A large difference in mobility between the WE and SE competing anions gives an SE with a higher final eluotropic strength, but the slope of the gradient is shallower. This results in a reduction in the efficiency of analyte focusing. To ensure maximum focusing efficiency, the WE and SE electrolytes should be selected such that the SE has the highest possible eluotropic strength for a given concentration of WE. The SE competing anion should also have a sufficiently low electrophoretic mobility to ensure focusing for the maximum number of analytes, and the mobility difference between the WE and SE competing anions should be as small as possible.

Capillary electrophoresis for automated on-line monitoring of suspension cultures: Correlating cell density, nutrients and metabolites in near real-time

Publisher: Elsevier BV

Date: 05-2016

DOI: 10.1016/J.ACA.2016.03.034

Abstract: Increasingly stringent demands on the production of biopharmaceuticals demand monitoring of process parameters that impact on their quality. We developed an automated platform for on-line, near real-time monitoring of suspension cultures by integrating microfluidic components for cell counting and filtration with a high-resolution separation technique. This enabled the correlation of the growth of a human lymphocyte cell line with changes in the essential metabolic markers, glucose, glutamine, leucine/isoleucine and lactate, determined by Sequential Injection-Capillary Electrophoresis (SI-CE). Using 8.1 mL of media (41 μL per run), the metabolic status and cell density were recorded every 30 min over 4 days. The presented platform is flexible, simple and automated and allows for fast, robust and sensitive analysis with low s le consumption and high s le throughput. It is compatible with up- and out-scaling, and as such provides a promising new solution to meet the future demands in process monitoring in the biopharmaceutical industry.

Preconcentration by solvent removal: techniques and applications

Publisher: Springer Science and Business Media LLC

Date: 07-01-2019

DOI: 10.1007/S00216-018-1530-8

Abstract: Preconcentration is the aspect of analytical method development covering the need to improve detection sensitivity. This review collects the advances in a ersity of approaches to achieve preconcentration by solvent removal. Evaporation in microfluidic and paper-based devices is reported in a variety of forms and later compared to membrane-assisted evaporation. S le partitioning in an immiscible fluid is also described. The reported methodologies highlight the need to achieve good control of the gas-liquid interface to obtain accurate results. A comprehensive comparison of different strategies is presented here discussing their benefits and drawbacks as well as the research needs in this area. Graphical abstract ᅟ.

High‐resolution computer simulations of EKC

Publisher: Wiley

Date: 02-2009

DOI: 10.1002/ELPS.200800671

Abstract: The electrophoresis simulation software, GENTRANS, has been modified to include the interaction of analytes with an electrolyte additive to allow the simulation of liquid-phase EKC separations. The modifications account for interaction of weak and strong acid and base analytes with a single weak or strong acid or base background electrolyte additive and can be used to simulate a range of EKC separations with both charged and neutral additives. Simulations of separations of alkylphenyl ketones under real experimental conditions were performed using mobility and interaction constant data obtained from the literature and agreed well with experimental separations. Migration times in fused-silica capillaries and linear polyacrylamide-coated capillaries were within 7% of the experimental values, while peak widths were always narrower than the experimental values, but were still within 50% of those obtained by experiment. Simulations of sweeping were also performed although migration time agreement was not as good as for simple EKC separations, peak widths were in good agreement, being within 1-50% of the experimental values. All simulations for comparison with experimental data were performed under real experimental conditions using a 47 cm capillary and a voltage of 20 kV and represent the first quantitative attempt at simulating EKC separations with and without sweeping.

Capillary electrophoresis evidence for the stereoselective metabolism of itraconazole in man

Publisher: Wiley

Date: 31-07-2003

DOI: 10.1002/ELPS.200305494

Abstract: Itraconazole (ITC) is a hydrophobic antimycotic drug with three chiral centers that is used clinically as a stereoisomeric mixture. A chiral capillary electrophoretic method for the separation of ITC stereoisomers and those of its main metabolite hydroxyitraconazole (HITC) was developed to determine the stereoselective nature of the ITC to HITC biotransformation. The method is based on the formation of inclusion complexes of the target analytes with the negatively charged sulfated beta-cyclodextrin in the presence of moderate concentrations of methanol in a low-pH phosphate buffer. The addition of polyethylene glycol 4000 was found to be critical in obtaining baseline resolution of eight peaks, two from ITC, four from HITC, and two from R051012 (internal standard), in under 20 min. Application of the developed procedure to serum s les from patients being treated with ITC showed clearly the presence of a stereoselective component in the metabolism of this antimycotic drug. This could be shown from in vitro incubations with single enzyme Supersomes to be in part due to the stereoselective formation of HITC by the human CYP3A4 enzyme. For one patient, monitoring of the ITC and HITC concentrations and peak ratios over a 103 day period of treatment with ITC showed a strong dependency of the chiral ITC ratio to the concentration of ITC, while the dominant enantiomeric ratio of HITC was largely independent of the total HITC concentration.

Manipulation of separation selectivity for alkali metals and ammonium in ion-exchange capillary electrochromatography using a suspension of cation exchange particles in the electrolyte as a pseudostationary phase

Publisher: Wiley

Date: 07-1999

DOI: 10.1002/(SICI)1522-2683(19990701)20:10<1987::AID-ELPS1987>3.0.CO;2-K

Isotachophoresis on a chip with indirect fluorescence detection as a field deployable system for analysis of carboxylic acids

Publisher: Wiley

Date: 12-10-2012

DOI: 10.1002/ELPS.201200141

Abstract: ITP with indirect fluorescence detection (IFD) was introduced three decades ago. Despite this fact, the method has never become widely adopted. The main aim of this work was to utilize the ITP-IFD for the separation of carboxylic acids by using a commercially available, portable, microfluidic chip electrophoresis system. On the 16.8-mm effective length separation channel, a maximum of eight carboxylic acids could be separated, with LOD values in a range from 0.12 to 0.4 mM. The commercial chips used for all experiments have multichannel structures important for analysis of more than one s le per a chip in case of standard use. This multichannel structure was used to investigate the possibility of multiple s le loading for ITP separation. Application of ITP-IFD was investigated for analysis of benzoate in diet soft drinks and the results were in good agreement with results of a CE method.

β-Cyclodextrin-copper (II) complex as chiral selector in capillary electrophoresis for the enantioseparation of β-blockers

Publisher: Elsevier BV

Date: 07-2019

DOI: 10.1016/J.CHROMA.2019.03.019

Abstract: The Copper (II) complex of β-cyclodextrin (β-CD), β-CDCu

Approaches to enhancing the sensitivity of capillary electrophoresis methods for the determination of inorganic and small organic anions

Publisher: Wiley

Date: 07-2001

DOI: 10.1002/1522-2683(200107)22:12<2464::AID-ELPS2464>3.0.CO;2-U

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2006–2008)

Publisher: Wiley

Date: 2009

DOI: 10.1002/ELPS.200800435

Abstract: Poor sensitivity is still considered to be one of the major limitations of electrophoresis, which is surprising given the power, flexibility and versatility of many of the approaches to on-line concentration that have developed over the last 20 years. This is still a very active area of interest and this review will cover developments in the field over the last two years since the last review (Electrophoresis 2007, 28, 254-281) through to June 2008. It includes developments in the fields of stacking, covering all methods from field- lified s le stacking and large volume s le stacking, through to ITP, dynamic pH junction and sweeping. Attention is also given to on-line or in-line extraction methods that have been used for electrophoresis.

Online sample pre-concentration via dynamic pH junction in capillary and microchip electrophoresis

Publisher: Wiley

Date: 10-2011

DOI: 10.1002/JSSC.201100414

Abstract: Various analytical techniques have been developed over the years to analyse a large ersity of biomolecules with a constant push towards ultra-sensitive detection. CE is at the forefront of the most powerful analytical tools available to date when considering its superior efficiency and resolution however, the technique suffers from poor sensitivity as a result of the short path length at the detection site and small injection volumes (typically <1% capillary length). One of the approaches to abate the inherent problem is to employ clever chemistry using s le focusing techniques whereby a large s le plug can be injected, preconcentrated and separated, producing excellent sensitivity and efficiency at the detector. This particular review will focus on the use of dynamic pH junction as a means of improving sensitivity in CE and focuses on the use of a change in analyte ionisation due to different pHs between the s le and electrolyte. The review provides a fundamental discussion of the mechanisms, buffer and s le conditions required to concentrate various analytes and a comprehensive list of published works in tabular format for easy identification of suitable conditions for new applications. The review further encompasses the use of dynamic pH junction in CE and its involvement in combination with other preconcentrations techniques to produce high sensitivity enhancements recorded between the years 1990-2010.

Towards a microchip-based chromatographic platform. Part 1: Evaluation of sol-gel phases for capillary electrochromatography

Publisher: Wiley

Date: 10-2002

DOI: 10.1002/1522-2683(200210)23:20<3487::AID-ELPS3487>3.0.CO;2-5

Micellar electrokinetic chromatography of organic and peroxide-based explosives

Publisher: Elsevier BV

Date: 05-2015

DOI: 10.1016/J.ACA.2015.02.070

Abstract: CE methods have been developed for the analysis of organic and peroxide-based explosives. These methods have been developed for deployment on portable, in-field instrumentation for rapid screening. Both classes of compounds are neutral and were separated using micellar electrokinetic chromatography (MEKC). The effects of s le composition, separation temperature, and background electrolyte composition were investigated. The optimised separation conditions (25 mM sodium tetraborate, 75 mM sodium dodecyl sulfate at 25°C, detection at 200 nm) were applied to the separation of 25 organic explosives in 17 min, with very high efficiency (typically greater than 300,000 plates m(-1)) and high sensitivity (LOD typically less than 0.5 mg L(-1) around 1-1.5 μM). A MEKC method was also developed for peroxide-based explosives (10 mM sodium tetraborate, 100 mM sodium dodecyl sulfate at 25°C, detection at 200 nm). UV detection provided LODs between 5.5 and 45.0 mg L(-1) (or 31.2-304 μM), which is comparable to results achieved using liquid chromatography. Importantly, no s le pre-treatment or post-column reaction was necessary and the peroxide-based explosives were not decomposed to hydrogen peroxide. Both MEKC methods have been applied to pre-blast analysis and for the detection of post-blast residues recovered from controlled, small scale detonations of organic and peroxide-based explosive devices.

Dynamic high‐resolution computer simulation of isotachophoretic enantiomer separation and zone stability

Publisher: Wiley

Date: 13-01-2014

DOI: 10.1002/ELPS.201300438

Abstract: The development of electrophoretic computer models and their use for simulation of electrophoretic processes has increased significantly during the last few years. Recently, GENTRANS and SIMUL5 were extended with algorithms that describe chemical equilibria between solutes and a buffer additive in a fast 1:1 interaction process, an approach that enables simulation of the electrophoretic separation of enantiomers. For acidic cationic systems with sodium and H3 0(+) as leading and terminating components, respectively, acetic acid as counter component, charged weak bases as s les, and a neutral CD as chiral selector, the new codes were used to investigate the dynamics of isotachophoretic adjustment of enantiomers, enantiomer separation, boundaries between enantiomers and between an enantiomer and a buffer constituent of like charge, and zone stability. The impact of leader pH, selector concentration, free mobility of the weak base, mobilities of the formed complexes and complexation constants could thereby be elucidated. For selected ex les with methadone enantiomers as analytes and (2-hydroxypropyl)-β-CD as selector, simulated zone patterns were found to compare well with those monitored experimentally in capillary setups with two conductivity detectors or an absorbance and a conductivity detector. Simulation represents an elegant way to provide insight into the formation of isotachophoretic boundaries and zone stability in presence of complexation equilibria in a hitherto inaccessible way.

Electrokinetics for sample preparation of biological molecules in biological samples using microfluidic systems

Publisher: Future Science Ltd

Date: 07-2014

DOI: 10.4155/BIO.14.140

Abstract: S le preparation is the first part of every analytical method, but is often considered only after the optimization of the method. It is traditionally performed using a range of techniques requiring extensive manual handling, with solid-phase extraction, liquid–liquid extraction, protein precipitation and ultracentrfiguation, among others, being used depending on the targets and the application. In this article, we will focus on alternatives based on electrokinetics for applications including s le clean-up, concentration and derivatization of large biological molecules (DNA, peptides and proteins) of diagnostic importance, as well as small molecules as a tool for therapeutic drug monitoring. This article describes these approaches in terms of mechanisms, applicability and potential to be integrated into a lab-on-a-chip device for directly processing biological s les. Ex les dealing with treated or clean s les have been excluded except where they show exceptionally high value.

Use of ionic polymers as stationary and pseudo-stationary phases in the separation of ions by capillary electrophoresis and capillary electrochromatography

Publisher: Elsevier BV

Date: 2002

DOI: 10.1016/S0021-9673(01)01403-0

Abstract: One of the problems with capillary electrophoresis is a lack of versatility regarding manipulation of the separation selectivity. A new and potentially universal concept is to introduce an ion-exchange component into a separation so that the migration of analyte ions is influenced by both their electrophoretic mobilities and their chromatographic properties. This may be accomplished by use of capillaries filled with or coated with solid ion-exchange polymers, or by addition of a soluble ionic polymer to the background electrolyte to create a pseudo-stationary phase. While each of these methods achieves the same result, they are not competitive, but rather complementary as the problems associated by one approach are overcome by the others. Recent highlights in the field are used to illustrate the flexibility that this approach provides to electrophoretic separation of ions.

Analysis of Melamine in Milk Powder and Liquid Milk by Capillary Zone Electrophoresis After Electrokinetic Supercharging

Publisher: Springer Science and Business Media LLC

Date: 17-10-2014

DOI: 10.1007/S12161-014-9987-3

Strategies for the on-line preconcentration and separation of hypolipidaemic drugs using micellar electrokinetic chromatography

Publisher: Elsevier BV

Date: 2010

DOI: 10.1016/J.CHROMA.2009.11.043

Abstract: Three strategies were investigated for the simultaneous separation and on-line preconcentration of charged and neutral hypolipidaemic drugs in micellar electrokinetic chromatography (MEKC). A background electrolyte (BGE) consisting of 20 mM ammonium bicarbonate buffer (pH 8.50) and 50 mM sodium dodecyl sulfate (SDS) was used for the separation and on-line preconcentration of the drugs. The efficiencies of sweeping, analyte focusing by micelle collapse (AFMC), and simultaneous field- lified s le stacking (FASS) and sweeping, were compared for the preconcentration of eight hypolipidaemic drugs in different conductivity s le matrices. When compared with a hydrodynamic injection (5 s at 50 mbar, 0.51% of capillary volume to detection window) of drug mixture prepared in the separation BGE, improvements of detection sensitivity of 60-, 83-, and 80-fold were obtained with sweeping, AFMC and simultaneous FASS and sweeping, respectively, giving limits of detection (LODs) of 50, 36, and 38 microg/L, respectively. The studied techniques showed suitability for focusing different types of analytes having different values of retention factor (k). This is the first report for the separation of different types of hypolipidaemic drugs by capillary electrophoresis (CE). The three methods were validated then applied for the analysis of target analytes in wastewater s les from Hobart city.

Integrated Microfluidic Devices Fabricated in Poly (Methyl Methacrylate) (PMMA) for On-site Therapeutic Drug Monitoring of Aminoglycosides in Whole Blood

Publisher: MDPI AG

Date: 30-01-2019

DOI: 10.3390/BIOS9010019

Abstract: On-site therapeutic drug monitoring (TDM) is important for providing a quick and accurate dosing to patients in order to improve efficacy and minimize toxicity. Aminoglycosides such as amikacin, gentamicin, and tobramycin are important antibiotics that have been commonly used to treat infections of chronic bacterial infections in the urinary tract, lung, and heart. However, these aminoglycosides can lead to vestibular and auditory dysfunction. Therefore, TDM of aminoglycosides is important due to their ototoxicity and nephrotoxicity. Here, we have developed a hot embossed poly (methyl methacrylate) (PMMA) microfluidic device featuring an electrokinetic size and mobility trap (SMT) to purify, concentrate, and separate the aminoglycoside antibiotic drugs amikacin, gentamicin, and tobramycin. These drugs were separated successfully from whole blood within 3 min, with 30-fold lower detection limits compared to a standard pinched injection. The limit of detections (LOD) were 3.75 µg/mL for gentamicin, 8.53 µg/mL for amikacin, and 6.00 µg/mL for tobramycin. These are sufficient to cover the therapeutic range for treating sepsis of 6–10 μg/mL gentamicin and tobramycin and 12–20 μg/mL of amikacin. The device is simple and could be mass produced via embossing or injection molding approaches.

Pulsed multi-wavelength excitation using fiber-in-capillary light emitting diode induced fluorescence detection in capillary electrophoresis

Publisher: Elsevier BV

Date: 15-12-2010

DOI: 10.1016/J.TALANTA.2010.09.047

Abstract: A novel instrument was developed using a multi-wavelength pulsed LED array with in-column optic-fiber induced fluorescence detection by capillary electrophoresis. The light from 2 different wavelength LEDs (450 nm and 480 nm) was pulsed for short intervals at high intensity. The beam from each LED was collimated and reshaped with the gradient index (GRIN) lens group to achieve a highly effective coupling between LED light source and an optical fiber. The optical fiber was placed inside the capillary for in-capillary LED-induced fluorescence detection. The advantages of this system were validated by the simultaneous determination of vitamin B2 and fluorescein. Detection limits for vitamin B2 and fluorescein were estimated to be 5 nM and 0.29 nM (S/N=3), respectively. The relative standard deviations (RSDs, n=6) of the both compounds for migration time and peak area were better than 0.83%, 2.20% and 1.21%, 2.75%, respectively. The method was applied to the determination of vitamin B2 in commercial tablets and fluorescein in fluorescein sodium injection and the recoveries obtained were in the range of 96.6-102.0% and 99.9-102.8%, respectively. It was also applied to human serum, where the recoveries were found to be in the range of 94.4-97.0% and 92.6-96.4%, respectively. The system has been successfully applied in separation and determination of the both biological s les with acceptable analytical performance.

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.

Analytical isotachophoresis of lactate in human serum using dry film photoresist microfluidic chips compatible with a commercially available field-deployable instrument platform

Publisher: Elsevier BV

Date: 11-2013

DOI: 10.1016/J.ACA.2013.01.046

Abstract: A dry film resist (DFR) chip compatible with the Agilent Bioanalyzer 2100 was designed and fabricated for use in the analysis of lactate in serum by chip isotachophoresis (ITP). The Agilent Bioanalyzer 2100 is a commercially available field deployable analytical instrument originally developed for the electrophoretic analysis of DNA, RNA and proteins. The DFR chip was designed for the ITP separation of lactate in human serum within 1 min and was made compatible with the Bioanalyzer after packaging in the plastic caddies normally used for the DNA chips. A 20-fold improvement in sensitivity was obtained for the DFR chips in comparison with the standard chips used in earlier work. The limit of detection and limit of quantification for lactate were 24 μM and 80 μM, respectively. This new approach enables the use of commercial platforms like the Agilent Bioanalyzer for new applications including the analysis of small molecules.

Counter-flow electrokinetic supercharging for the determination of non-steroidal anti-inflammatory drugs in water samples

Publisher: Elsevier BV

Date: 04-2009

DOI: 10.1016/J.CHROMA.2009.02.014

Abstract: Electrokinetic supercharging (EKS) has been used in the last few years as a powerful tool for separation and on-line preconcentration of different types of analytes. We have developed a valuable modification for EKS system, namely counter-flow EKS (CF-EKS) and applied it for the separation and on-line preconcentration of seven non-steroidal anti-inflammatory drugs (NSAIDs) in water s les. In CF-EKS, a hydrodynamic counter-flow is applied during electrokinetic injection of the analytes within the EKS system. This counter-flow minimises the introduction of the s le matrix into the capillary, allowing longer injections to be performed. Careful choice of the optimum counter-flow as well as the optimum injection voltage allowed the sensitivity to be enhanced by 11,800-fold, giving limits of detection (LODs) of 10.7-47.0 ng/L for the selected NSAIDs. The developed method was validated and then applied for the determination of the studied NSAIDs in drinking water as well as wastewater s les from Hobart city.

Characterisation of graphene fibres and graphene coated fibres using capacitively coupled contactless conductivity detector

Publisher: Royal Society of Chemistry (RSC)

Date: 2016

DOI: 10.1039/C5AN02534F

Abstract: The use of capacitively coupled contactless conductivity detection (C 4 D) for the characterisation of thin conductive graphene fibres, graphene composite fibres, and graphene coated fibrous materials is demonstrated for the first time.

Principles around Accurate Blood Volume Collection Using Capillary Action

Publisher: American Chemical Society (ACS)

Date: 06-12-2017

DOI: 10.1021/ACS.LANGMUIR.7B02825

Abstract: Capillary action is one mechanism microfluidics uses to draw liquid autonomously in a substrate without the need of external energy. This behavior can be exploited to collect accurate volumes of liquids such as blood in narrow columns known as capillary tubes and help the development of inexpensive, user-friendly personalized biomedical tools. Precision bore glass capillaries demonstrate the "state of the art" for volume accuracy and precision, but height and radius must be carefully chosen in order to exploit the capillary action behavior efficiently. This Article investigates the influence of surface glass aging, due to prolonged exposure to humid air, and hematocrit level on the blood capillary rise. It provides also the tools to correctly define the optimum capillary dimensions to collect an accurate volume of blood in a glass capillary tube.

Indirect spectrophotometric detection of inorganic anions in ion-exchange capillary electrochromatography

Publisher: Wiley

Date: 09-2000

DOI: 10.1002/1522-2683(20000901)21:15<3073::AID-ELPS3073>3.0.CO;2-H

In‐Syringe Electrokinetic Protein Removal from Biological Samples prior to Electrospray Ionization Mass Spectrometry

Publisher: Wiley

Date: 13-10-2020

DOI: 10.1002/ANIE.202006481

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

White LEDs as broad spectrum light sources for spectrophotometry: Demonstration in the visible spectrum range in a diode-array spectrophotometric detector

Publisher: Wiley

Date: 11-2010

DOI: 10.1002/ELPS.201000341

Abstract: Although traditional l s, such as deuterium l s, are suitable for bench-top instrumentation, their compatibility with the requirements of modern miniaturized instrumentation is limited. This study investigates the option of utilizing solid-state light source technology, namely white LEDs, as a broad band spectrum source for spectrophotometry. Several white light LEDs of both RGB and white phosphorus have been characterized in terms of their emission spectra and energy output and a white phosphorus Luxeon LED was then chosen for demonstration as a light source for visible-spectrum spectrophotometry conducted in CE. The Luxeon LED was fixed onto the base of a dismounted deuterium (D(2) ) l so that the light-emitting spot was geometrically positioned exactly where the light-emitting spot of the original D(2) l is placed. In this manner, the detector of a commercial CE instrument equipped with a DAD was not modified in any way. As the detector hardware and electronics remained the same, the change of the deuterium l for the Luxeon white LED allowed a direct comparison of their performances. Several anionic dyes as model analytes with absorption maxima between 450 and 600 nm were separated by CE in an electrolyte of 0.01 mol/L sodium tetraborate. The absorbance baseline noise as the key parameter was 5 × lower for the white LED l , showing clearly superior performance to the deuterium l in the available, i.e. visible part of the spectrum.

Artificial neural networks for computer-aided modelling and optimisation in micellar electrokinetic chromatography

Publisher: Elsevier BV

Date: 07-1999

DOI: 10.1016/S0021-9673(99)00634-2

Abstract: The separation process in capillary micellar electrochromatography (MEKC) can be modelled using artificial neural networks (ANNs) and optimisation of MEKC methods can be facilitated by combining ANNs with experimental design. ANNs have shown attractive possibilities for non-linear modelling of response surfaces in MEKC and it was demonstrated that by combining ANN modelling with experimental design, the number of experiments necessary to search and find optimal separation conditions can be reduced significantly. A new general approach for computer-aided optimisation in MEKC has been proposed which, because of its general validity, can also be applied in other separation techniques.

Theoretical migration model for micellar capillary electrophoresis and its application to the separation of anionic metal complexes of HEDTC and CDTA

Publisher: American Chemical Society (ACS)

Date: 27-03-1999

DOI: 10.1021/AC981044H

Abstract: A mathematical model relating the effective mobility of an analyte in micellar capillary electrophoresis (MCE) to the concentration of surfactant and organic modifier in the background electrolyte (BGE) was derived. Effective mobility is expressed in terms of the electrophoretic mobility of the analyte, the partition coefficient of the analyte into the micelle, and the influence of organic modifier on these two factors. The performance of the model was evaluated using Cd(II), Pb(II), Co(II), Ni(II), Bi(III), Cu(II), and Hg(II) complexes of bis(2-hydroxyethyl)dithiocarbamate, all of which carry a partial negative charge, and Cd(II), Pb(II), Co(II), Ni(II), Bi(III), Cu(II), Hg(II), Fe(III), Ag(I), Tl(I), and Mn(II) complexes of trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid, all of which are anionic having charges in the range -1 to -3. These analytes were separated in borate BGEs containing 10-50 mM sodium dodecyl sulfate and 0-20% (v/v) methanol. Nonlinear regression was used to derive parameters for the model from experimental data and these parameters were used to predict effective mobilities of the analytes. Predicted values of effective mobilties agreed with experimental values to within 3.1%. Values of parameters from the model equation are used to explain changes in separation selectivity observed at different BGE compositions and the model equation is shown to be applicable to computer-assisted optimization of the BGE composition, in MCE using a limited number of experiments.

Colorimetric determination of perfluorocarboxylic acids using porphyrin hosts and mobile phone photographs

Publisher: Royal Society of Chemistry (RSC)

Date: 2023

DOI: 10.1039/D3SD00035D

Abstract: Functionalized porphyrin molecules were found to change color in the presence of perfluorocarboxylic acids (PFCAs). The porphyrin molecules allow for simple visual- and color space-based detection of PFCAs across a range of concentrations.

Open-tubular ion-exchange capillary electrochromatography of inorganic anions

Publisher: Royal Society of Chemistry (RSC)

Date: 2000

DOI: 10.1039/B002173N

Electrokinetic supercharging in nonaqueous capillary electrophoresis for online preconcentration and determination of tamoxifen and its metabolites in human plasma

Publisher: Elsevier BV

Date: 08-2016

DOI: 10.1016/J.CHROMA.2016.07.067

Abstract: An online preconcentration method, namely electrokinetic supercharging (EKS), was evaluated for the determination of tamoxifen and its metabolites in human plasma in nonaqueous capillary electrophoresis with ultraviolet detection (NACE-UV). This method was comprehensively optimized in terms of the leading electrolyte (LE) and terminating electrolyte (TE) injection lengths, as well as electrokinetic s le injection time. The optimized EKS conditions employed were as follows: hydrodynamic injection (HI) of 10mM potassium chloride as LE at 150mbar for 36s (4% of total capillary volume). The s le was injected at 10kV for 300s, followed by HI of 10mM pimozide as TE at 150mbar for 36s (4% of total capillary volume). Separation was performed in 7.5mM deoxycholic acid sodium salt, 15mM acetic acid and 1mM 18-crown-6 in 100% methanol at +25kV with UV detection at 205nm. Under optimized conditions, the sensitivity was enhanced between 160- and 600-fold when compared with our previously developed method based on HI at 150mbar for 12s. The detection limit of the method for tamoxifen and its metabolites were 0.05-0.25ng/mL, with RSDs between 2.1% and 3.5%. Recoveries in spiked human plasma were 95.6%-99.7%. A comparison was also made between the proposed EKS approach and the standard field- lified s le injection (FASI) technique. EKS proved to be 3-5 times more sensitive than the FASI. The new EKS method was applied to the analysis of tamoxifen and its metabolites in plasma s les from breast cancer patients after liquid-liquid extraction.

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.

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.

Analysis of aromatic acids by nonaqueous capillary electrophoresis with ionic‐liquid electrolytes

Publisher: Wiley

Date: 13-10-2014

DOI: 10.1002/ELPS.201400242

Abstract: The separation of six kinds of aromatic acids by CZE with 1-ethyl-3-methylimidazolium chloride (EMIMCl) and 1-ethyl-3-methylimidazolium hydrogen sulfate (EMIMHSO4 ), two kinds of ionic liquids (ILs) as background electrolytes, and acetonitrile as solvent were investigated. The six kinds of aromatic acids can be separated under positive voltage with low IL concentration with either of the two ILs and separation with EMIMHSO4 is better in consideration of peak shapes and separation efficiency. But the migration order is different when the IL is different. Under negative voltage with high IL concentration, the six analytes can be separated with EMIMCl as background electrolytes and the migration order of the analytes is opposite to those with low concentration of EMIMCl as background electrolyte. The separations are based on the combination effects of heteroconjugation between the anions and cations in the ILs and the analytes, of which the heteroconjugation between the anions in the ILs and the analytes plays a dominant role. The heteroconjugation between the anions of the ILs and analytes is proton sensitive and only a very small amount of proticsolvents added into the electrolyte solution can harm the separation. When EMIMCl concentration is high, the heteroconjugation between the IL anions and the proton in the analytes make the effective mobility of the analytes much higher than the EOF and their migration direction reversed. Finally, the six aromatic acids in water s les were analyzed by nonaqueous CE with low concentration of EMIMHSO4 as background electrolytes with satisfactory results.

Analysis of brazilin and protosappanin B in sappan lignum by capillary zone electrophoresis with acid barrage stacking

Publisher: Wiley

Date: 09-2013

DOI: 10.1002/ELPS.201300402

Abstract: A method was developed to determine brazilin and protosappanin B in natural products by CE after acid barrage stacking. The optimum conditions were as follows: a BGE of 20 mM sodium tetraborate (pH 9.2) containing 6% v/v of methanol, hydrodynamic injection (0.5 psi, 65 s) followed by hydrodynamic injection of 150 mM citric acid (pH 2.3 0.5 psi, 22 s), and separated with +25 kV. Under these conditions, brazilin and protosappanin B were separated with a s le-to-s le time less than 13 min and detection limits of 0.28 μg/mL and 0.15 μg/mL, respectively. The applicability of the developed method was demonstrated by the detection of brazilin and protosappanin in methanol extract of sappan lignum.

Dual wavelength excitation fluorescence detector for capillary electrophoresis using a pulsed bi-colour light emitting diode

Publisher: Royal Society of Chemistry (RSC)

Date: 2011

DOI: 10.1039/C0AN00772B

Abstract: A simple and novel two-colour fluorescence detector for capillary electrophoresis was created using a single bi-colour light emitting diode (LED), multi-band pass excitation and emission filters and a single detector. Excitation light from a blue/red (470/635 nm) bi-colour LED was filtered through a 390/482/563/640 nm multi-band bandpass filter, with emitted light filtered through a 446/523/600/677 nm multi-band bandpass filter before being detected using a photon counting detector. Sequential pulsing of the blue/red LED and deconvolution of the collected fluorescence data allowed extracted electropherograms to be obtained corresponding to excitation with the blue and red LEDs. Optimisation of the pulsed LED conditions revealed an optimum LED on-time of 50 ms, off-time of 30 ms with a pulsed current of 40 mA, giving an effective data acquisition rate of 6.25 Hz. The characteristics of this system were validated by the simultaneous separation and determination of six fluorescent dyes: fluorescein, FITC, coumarin 334, dibromo(R)fluorescein (Ex/Em 470/525 nm), and Cy 5 and the Agilent Bioanalyser DNA dye (Ex/Em 635/670 nm). Under optimum conditions, the detection limits for FITC, fluorescein and Cy 5 were 69 nM, 42 nM and 289 nM (S/N = 3), respectively. These were lower than those obtained with continuous operation of the in idual wavelengths at a constant current of 20 mA, but were slightly higher than those obtained using dedicated single wavelength filter combinations designed specifically for use with these fluorophores. The intraday repeatability (n = 6) of migration times was less than 1.0% and less than 3.4% for peak areas, while interday (n = 3) migration time and peak area reproducibility were less than 0.9% and 3.6%, respectively. This simple detector is capable of performing quantitative two-wavelength excitation without the need for complex optics and light source configurations.

Capillary electrophoretic system of ribonucleic acid molecules

Publisher: Elsevier BV

Date: 12-2012

DOI: 10.1016/J.CHROMA.2012.08.017

Abstract: Over the past two decades, capillary electrophoresis (CE) has been the subject of extensive development and progress in various DNA based sieving electrophoresis applications, namely Sanger sequencing, forensic short tandem repeat (STR) analysis, clinical genotype screening (SNP), and phylogenetic fingerprinting. Yet, this trend has not been emulated in the RNA field. This review will highlight the development and key analysis parameters of RNA electrophoresis by CE and provide possible explanations for the low research interest in this area.

Isotachophoretic Fluorescence in Situ Hybridization of Intact Bacterial Cells

Publisher: American Chemical Society (ACS)

Date: 06-06-2017

DOI: 10.1021/ACS.ANALCHEM.7B00598

Abstract: A counter-pressure-assisted capillary isotachophoresis method in combination with a sieving matrix and ionic spacer was used to perform in-line fluorescence in situ hybridization (FISH) of bacterial cells. A high concentration of sieving matrix (1.8% w/v HEC) was introduced at one end of the capillary, and the bacterial cells were suspended in the spacer electrolyte for injection. Using a 2 min injection with 18 psi counter-pressure, 50% of the cells injected into the capillary were hybridized with the fluorescently labeled oligonucleotide, and the excess unhybridized probe was separated from the hybridized cell-probe complexes in a two-stage ITP method. With an LOD (6.0 × 10

Modelling and optimization of the separation of anions in ion chromatography - capillary electrophoresis

Publisher: Wiley

Date: 09-2000

DOI: 10.1002/1522-2683(20000901)21:15<3181::AID-ELPS3181>3.0.CO;2-L

In‐Transit Electroextraction of Small‐Molecule Pharmaceuticals from Blood

Publisher: Wiley

Date: 12-02-2019

DOI: 10.1002/ANIE.201812077

Abstract: An electrokinetic platform was developed for extracting small-molecule pharmaceuticals from a dried blood spot. Through the exclusion of liquid reagents and use of low field strength (6 V cm

Inexpensive portable capillary electrophoresis instrument for Monitoring Zinc(II) in remote areas

Publisher: Elsevier BV

Date: 04-2022

DOI: 10.1016/J.CHROMA.2022.462895

Abstract: A compact, inexpensive capillary electrophoresis instrument was developed for monitoring metal ions and evaluated for Zn(II) in remote contaminated locations in western Tasmania, Australia. The portable instrument, measuring 21 cm x 10 cm x 7 cm, was powered from the USB port of a laptop computer and built from off-the-shelf components costing ∼$1200 USD. Electrophoretic separations were conducted using a fused silica capillary (10-50 µm I.D.), applying 8.5 kV over capillaries ranging from 25 cm to 40 cm in length. The capillary inlet was connected with an electrically grounded cross-piece as flow-through injection interface. Automated fluidic management was achieved by controlling four mini peristaltic pumps and a solenoid valve. Detection was realised using a purpose-built visible LED absorption detector, optimised for the detection of Co(II), Cu(II) and Zn(II) after complexation with 4-(2-Pyridylazo) resorcinol (PAR). Limits of detection of sub-µM were obtained. The instrument was tested for continuous operation in the laboratory for up to 3 months, and relative standard deviations of <5.4% were found over 945 consecutive injections. In the field, the system was able to measure 106 s les within 11 h, the time it can be powered from the laptop computer. As Field measurement of Zn(II) in western Tasmania was demonstrated to show capability for on-site metal testing.

Electrokinetic supercharging for on-line preconcentration of seven non-steroidal anti-inflammatory drugs in water samples

Publisher: Elsevier BV

Date: 05-2008

DOI: 10.1016/J.CHROMA.2007.12.056

Abstract: The development of new sensitive methods for the analysis of non-steroidal anti-inflammatory drugs (NSAIDs) in water s les is of great importance. In this work, seven NSAIDs were separated within 9 min using 15 mM sodium tetraborate (pH 9.2) containing 0.1% (w/v) hexadimethrine bromide (HDMB) and 10% (v/v) methanol. Field- lified s le injection (FASI) was examined and found to improve the detection limits by 200-fold providing detection limits of 0.6-2.0 microg/L, but these are insufficient for the determination of NSAIDs as environmental pollutants in water s les. To improve the sensitivity further, electrokinetic supercharging (EKS) was examined. The optimum EKS method involved hydrodynamic injection leading electrolyte (100 mM NaCl, 30 s, 50 mbar), electrokinetic injection of the s le (200 s, -10 kV) and finally injection of the terminating electrolyte (100 mM 2-(cyclohexylamino) ethanesulphonic acid, CHES, 40s, 50 mbar). With this method, the sensitivity was improved by 2400-fold giving detection limits of 50-180 ng/L. The developed method was validated and then applied to the analysis of wastewater s les from a local sewage treatment plant. The detection limits were found to increase by approximately 10-fold, however, this is still lower than levels previously found in wastewater s les from European and Mediterranean cities. The proposed method has the advantage of simplicity and achieving sensitivity through high-preconcentration power without the use of off-line chromatographic s le cleanup.

Automated liquid-liquid extraction of organic compounds from aqueous samples using a multifunction autosampler syringe

Publisher: Elsevier BV

Date: 04-2021

DOI: 10.1016/J.CHROMA.2021.462032

Multidimensional liquid-phase separations combining both chromatography and electrophoresis – A review

Publisher: Elsevier BV

Date: 2020

DOI: 10.1016/J.ACA.2016.10.025

Abstract: Described as intrinsically powerful building blocks for two-dimensional separations by Giddings [Anal. Chem., 56 (1984) 1258A-1270A], the coupling of chromatography and electrophoresis has been proven to enhance the resolution of a wide array of molecules in complex biological, environmental and food s les. This review provides a comprehensive overview of multidimensional chromato-electrophoretic (LC - E) and electrophero-chromatographic (E - LC) separation systems from inception to the most recent published ex les. LC separation modes include reversed phase, ion exchange, and size exclusion. Electromigration separation modes include capillary, microchip or free flow electrophoresis micellar electrokinetic chromatography electrochromatography and isoelectric focusing. The advantages and disadvantages of various non-gel based off-line and on-line hyphenation technologies of LC - E and E - LC are discussed, with conditions and system characteristics also provided.

Novel Instrument for Automated pK_a Determination by Internal Standard Capillary Electrophoresis

Publisher: American Chemical Society (ACS)

Date: 29-05-2015

DOI: 10.1021/ACS.ANALCHEM.5B00845

Abstract: The internal standard capillary electrophoresis method (IS-CE) has been implemented in a novel sequential injection-capillary electrophoresis instrument for the high-throughput determination of acidity constants (pK(a)) regardless of aqueous solubility, number of pK(a) values, or structure. This instrument comprises a buffer creation system that automatically mixes within a few seconds four reagents for in situ creation of the separation electrolyte with a pH range of 2-13, ionic strength of 10-100 mM and organic solvent content from 0% to 40%. Combined with 1.2 kV/cm and a short effective length (15 cm to the UV detector) fast 20 s electrophoretic separations can be obtained. The low standard deviation of the replicates and the low variation compared to reference values show that this system can accurately determine acidity constants of drugs by IS-CE. A single pK(a) can be determined in 2 min and a set of 20 measurements in half an hour, allowing rapid, simple, and flexible determination of pK(a) values of pharmaceutical targets.

Ionic liquid-based liquid phase microextraction with direct injection for capillary electrophoresis

Publisher: Elsevier BV

Date: 03-2011

DOI: 10.1016/J.CHROMA.2011.01.019

Abstract: Liquid-liquid microextraction using the water immiscible ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, EMIM NtfO₂, for the concentration and cleanup of basic compounds for analysis by CE has been investigated. Using an electrolyte comprising 1 mol/L alanine and 3 mol/L acetic acid, EMIM NtfO₂ could be directly injected into the capillary after liquid phase extraction. Using the basic dye chryisoidine, sensitivity enhancements approaching 1000-fold were obtained by mixing 20 μL of EMIM NtfO₂ with 1500 μL of aqueous s le, leaving only 5 μL of the undissolved ionic liquid which was used for injection into the CE. Lower more repeatable enhancement factors of 200-fold were obtained with slightly larger initial 25 μL volumes of EMIM NtfO₂ due to the larger residual volume of ionic liquid which made handling easier. This could be extended to basic pharmaceuticals, and the extraction of clozapine and its two active metabolites, nor-clozapine and clozapine-N-oxide, was demonstrated from urine with enrichment factors greater than 100 obtained. Handling of potentially more dangerous s les, such as serum, through in-vial extraction of clozapine and its metabolites and direct injection of the ionic liquid layer was also demonstrated with enhancements in sensitivity of 80. Limits of detection from 3 to 11 μg/L and 6 to 55 μg/L were obtained from urine and serum, respectively, which are sufficiently low to be useful for the determination of these pharmaceuticals clinically for therapeutic drug monitoring and for forensic toxicology.

Boronate functionalised polymer monoliths for microscale affinity chromatography

Publisher: Royal Society of Chemistry (RSC)

Date: 2006

DOI: 10.1039/B609051F

Abstract: Novel macroporous monolithic stationary phase materials suitable for microscale boronate affinity chromatography were developed.

The role of gratitude in enhancing the relationship between doctoral research students and their supervisors

Publisher: Informa UK Limited

Date: 05-01-2017

DOI: 10.1080/13562517.2016.1273212

Dynamic computer simulations of electrophoresis: A versatile research and teaching tool

Publisher: Wiley

Date: 26-02-2010

DOI: 10.1002/ELPS.200900613

Abstract: Software is available, which simulates all basic electrophoretic systems, including moving boundary electrophoresis, zone electrophoresis, ITP, IEF and EKC, and their combinations under almost exactly the same conditions used in the laboratory. These dynamic models are based upon equations derived from the transport concepts such as electromigration, diffusion, electroosmosis and imposed hydrodynamic buffer flow that are applied to user-specified initial distributions of analytes and electrolytes. They are able to predict the evolution of electrolyte systems together with associated properties such as pH and conductivity profiles and are as such the most versatile tool to explore the fundamentals of electrokinetic separations and analyses. In addition to revealing the detailed mechanisms of fundamental phenomena that occur in electrophoretic separations, dynamic simulations are useful for educational purposes. This review includes a list of current high-resolution simulators, information on how a simulation is performed, simulation ex les for zone electrophoresis, ITP, IEF and EKC and a comprehensive discussion of the applications and achievements.

Droplet Microfluidics for Postcolumn Reactions in Capillary Electrophoresis

Publisher: American Chemical Society (ACS)

Date: 11-11-2014

DOI: 10.1021/AC5033963

Abstract: A postcolumn reaction system based on droplet microfluidics was developed for capillary electrophoresis (CE). Analytes were separated using capillary zone electrophoresis (CZE) and electrophoretically transferred into droplets. The use of a micro cross for positioning a salt bridge-electrode opposite the separation capillary outlet is the key element for maintaining the electrical connection during electrophoretic separation. As the first of its kind, positioning the droplets in the electric field eliminated the need for electroosmotic flow (EOF) or hydrodynamic flow for droplet compartmentalization. Depending on the total flow rate of both aqueous and oil phases, droplets of water-in-oil could be formed having frequencies between 0.7 and 3.7 Hz with a size of approximately 14 nL per droplet. Compartmentalized in the droplets, analytes reacted with reagents already present in the droplets to facilitate detection. The periodate oxidation of paralytic shellfish toxins (PSTs) was demonstrated, overcoming the limitation of precolumn oxidation, which results in multiple and sometimes identical oxidation products formed from the different PSTs. Compartmentalization allows the oxidation products for each peak to be contained and to contribute to a single fluorescence signal, preserving the selectivity of CZE separation while gaining the sensitivity of fluorescence detection.

Dynamic computer simulations of electrophoresis: Three decades of active research

Publisher: Wiley

Date: 06-2009

DOI: 10.1002/ELPS.200900058

Abstract: Dynamic models for electrophoresis are based upon model equations derived from the transport concepts in solution together with user-inputted conditions. They are able to predict theoretically the movement of ions and are as such the most versatile tool to explore the fundamentals of electrokinetic separations. Since its inception three decades ago, the state of dynamic computer simulation software and its use has progressed significantly and Electrophoresis played a pivotal role in that endeavor as a large proportion of the fundamental and application papers were published in this periodical. Software is available that simulates all basic electrophoretic systems, including moving boundary electrophoresis, zone electrophoresis, ITP, IEF and EKC, and their combinations under almost exactly the same conditions used in the laboratory. This has been employed to show the detailed mechanisms of many of the fundamental phenomena that occur in electrophoretic separations. Dynamic electrophoretic simulations are relevant for separations on any scale and instrumental format, including free-fluid preparative, gel, capillary and chip electrophoresis. This review includes a historical overview, a survey of current simulators, simulation ex les and a discussion of the applications and achievements of dynamic simulation.

Tuneable nanochannel formation for sample-in/answer-out devices

Publisher: Royal Society of Chemistry (RSC)

Date: 2013

DOI: 10.1039/C3CC38330J

Abstract: Control of the dielectric breakdown of PDMS was achieved by limiting the current during the breakdown process. This enabled tuning of the nanochannel pore size and hence their permeability for molecules of different molecular weights. This method enabled the analysis of the drug quinine from whole blood in 3 min using a simple, disposable microfluidic device.

Integrated 3D printed heaters for microfluidic applications: Ammonium analysis within environmental water

Publisher: Elsevier BV

Date: 02-2020

DOI: 10.1016/J.ACA.2019.11.025

Abstract: A multi-material 3D printed microfluidic reactor with integrated heating is presented, which was applied within a manifold for the colorimetric determination of ammonium in natural waters. Graphene doped polymer was used to provide localised heating when connected to a power source, achieving temperatures of up to 120 °C at 12 V, 0.7 A. An electrically insulating layer of acrylonitrile butadiene styrene (ABS) polymer or a new microdiamond-ABS polymer composite was used as a heater coating. The microdiamond polymer composite provided higher thermal conductivity and uniform heating of the serpentine microreactor which resulted in greater temperature control and accuracy in comparison to pure ABS polymer. The developed heater was then applied and demonstrated using a modified Berthelot reaction for ammonium analysis, in which the microreactor was configured at a predetermined optimised temperature. A 5-fold increase in reaction speed was observed compared to previously reported reaction rates. A simple flow injection analysis set up, comprising the microfluidic heater along with an LED-photodiode based optical detector, was assembled for ammonium analysis. Two river water s les and two blind ammonium standards were analysed and estimated concentrations were compared to concentrations determined using benchtop IC. The highest relative error observed following the analysis of the environmental s les was 11% and for the blind standards was 5%.

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%).

Analysis of the disaccharides derived from hyaluronic acid and chondroitin sulfate by capillary electrophoresis with sample stacking

Publisher: Wiley

Date: 11-2005

DOI: 10.1002/JSSC.200500181

Abstract: CE conditions for monitoring the unsaturated disaccharides of hyaluronic acid (di-HA) and chondroitin sulfate (di-CS) using an alkaline tetraborate buffer, electrokinetic s le injection, and UV absorption detection at 232 nm are reported. Separations were performed in an uncoated fused-silica capillary having reversed polarity and reversed electroosmosis generated with the addition of CTAB to the buffer. The influence of various separation parameters, including the concentration of CTAB, buffer pH, concentration of tetraborate, and applied voltage, on the resolution of the two disaccharides was investigated. Baseline separation was obtained with 25 mM tetraborate at pH 10.0 and having 0.05 mM CTAB. Chloride and phosphate in the s le are beneficial for the stacking of the disaccharides, with di-HA forming a much sharper peak than di-CS. Using s les prepared in 25 mM Tris-HCl (pH 7.5) and electrokinetic injection at the cathode at -10 kV for 40 s, linear relationships between the corrected peak area and the concentration of the disaccharides have been found in the ranges of 1.0-400.0 and 0.1-1.0 microg/mL (0.2-1.0 microg/mL for di-CS), with correlation coefficients being >0.9933 in all cases. The RSDs of detection times and corrected peak areas were between 1.13-1.24 and 1.57-2.13%, respectively. Applied to human serum s les that were prepared by ethanol precipitation and depolymerization of the two polysaccharides with chondroitinase ABC reveals comigration of endogenous compounds with di-HA and a s le-dependent detection time. The di-HA content in the serum s le can be estimated via subtraction of the blank peak that is obtained without enzymatic hydrolysis.

On-column ion-exchange preconcentration of inorganic anions in open tubular capillary electrochromatography with elution using transient-isotachophoretic gradients. 3. Implementation and method development

Publisher: American Chemical Society (ACS)

Date: 22-03-2002

DOI: 10.1021/AC011217U

Abstract: A solid-phase extraction method based on an ion-exchange retention mechanism has been used for in-line preconcentration of inorganic anions prior to their separation by capillary electrophoresis (CE). A single capillary containing a preconcentration and a separation zone has been used in a commercial CE instrument without instrumental modification. Analyte anions were retained on a preconcentration zone comprising an adsorbed layer of cationic latex particles, while separation was achieved in a separation zone comprising fused silica modified by adsorption of a cationic polymer. Elution of the adsorbed analytes was achieved using an eluotropic gradient formed by a transient isotachophoretic boundary between a fluoride electrolyte and a naphthalenedisulfonate electrolyte. Optimization of the electrolyte concentrations, s le injection times, and back-flushing times allowed the successful separation of sub-ppb levels of inorganic anions using a 100-min injection at 2 bar pressure, introducing over 40 capillary volumes of s le. A method based on a 10-min injection allowed a 100-fold increase in sensitivity over conventional hydrodynamic injection for Br-, I-, NO3-, CrO4(2-), and MoO4(2-) with a total analysis time of 25 min. Detection limits were dependent on the injection time but were in the range 2.2-11.6 ppb for a 10-min injection time. This approach was used to determine NO3- in Antarctic ice cores where the analysis could be performed using a s le volume 100 times less than that used for ion chromatography.

Exploring chip-capillary electrophoresis-laser-induced fluorescence field-deployable platform flexibility: Separations of fluorescent dyes by chip-based non-aqueous capillary electrophoresis

Publisher: Elsevier BV

Date: 04-2013

DOI: 10.1016/J.CHROMA.2013.02.060

Abstract: Microfluidic chip electrophoresis (chip-CE) is a separation method that is compatible with portable and on-site analysis, however, only few commercial chip-CE systems with laser-induced fluorescence (LIF) and light emitting diode (LED) fluorescence detection are available. They are established for several application tailored methods limited to specific biopolymers (DNA, RNA and proteins), and correspondingly the range of their applications has been limited. In this work we address the lack of commercially available research-type flexible chip-CE platforms by exploring the limits of using an application-tailored system equipped with chips and methods designed for DNA separations as a generic chip-CE platform - this is a very significant issue that has not been widely studied. In the investigated Agilent Bioanalyzer chip-CE system, the fixed components are the Agilent chips and the detection (LIF at 635 nm and LEDIF at 470 nm), while the chemistry (electrolyte) and the programming of all the high voltages are flexible. Using standard DNA chips, we show that a generic CE function of the system is easily possible and we demonstrate an extension of the applicability to non-aqueous CE (NACE). We studied the chip compatibility with organic solvents (i.e. MeOH, ACN, DMF and DMSO) and demonstrated the chip compatibility with DMSO as a non-volatile and non-hazardous solvent with satisfactory stability of migration times over 50h. The generic CE capability is illustrated with separations of fluorescent basic blue dyes methylene blue (MB), toluidine blue (TB), nile blue (NB) and brilliant cresyl blue (BC). Further, the effects of the composition of the background electrolyte (BGE) on the separation were studied, including the contents of water (0-30%) and buffer composition. In background electrolytes containing typically 80 mmol/L ammonium acetate and 870 mmol/L acetic acid in 100% DMSO baseline separation of the dyes were achieved in 40s. Linearity was documented in the range of 5-28 μmol/L, 10-100 μmol/L, 1.56-50 nmol/L and 5-75 nmol/L (r(2) values in the range 0.974-0.999), and limit of detection (LOD) values were 90 nmol/L, 1 μmol/L 1.4 nmol/L, and 2 nmol/L for MB, TB, NB and BC, respectively.

Photolithographic patterning of conducting polyaniline films via flash welding

Publisher: Elsevier BV

Date: 07-2010

DOI: 10.1016/J.SYNTHMET.2010.04.018

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips

Publisher: Wiley

Date: 2007

DOI: 10.1002/ELPS.200600463

Abstract: Poor sensitivity is considered to be one of the major limitations of electrophoretic separation methods, particularly when compared to traditional liquid chromatographic techniques. To address this issue, various in‐line preconcentration techniques have been developed over the past 15 years, ranging in power and complexity, and there are now a number of well understood approaches routinely capable of providing a 10 000‐ to 100 000‐fold increase in sensitivity, as well as several that can be pushed above a million. Furthermore, these have been achieved with particularly troublesome and often difficult s les, such as those having high salinity from a biological or environmental origin. This review will discuss the most common methods for improving the sensitivity of CE, CEC and microchip version of these, with particular attention to those approaches developed over the last five years.

A three-dimensional printed electromembrane extraction device for capillary electrophoresis

Publisher: Elsevier BV

Date: 06-2019

DOI: 10.1016/J.CHROMA.2019.02.023

Abstract: A concentric electromembrane extraction preconcentration device was designed and fabricated using fused deposition modelling 3D printing. The device consisted of a hemispherical electrode s le vial printed from a filament of conductive polylactic acid (PLA), into which sat a smaller hemispherical 3D printed porous membrane acceptor vial. Application of voltage between a point-electrode placed in the center of 20 μL solution inside the acceptor vial and the electrode vial containing 1 mL of s le, enabled anion migration through the 3D printed porous material into the acceptor solution. Electromembrane extraction was proved using fluorescein for imaging of the extraction process, with preconcentration rates of 0.833 μM/sec at 120 V with close to 95% recovery. The performance of the fabricated porous 3D printed device was evaluated for the preconcentration of anions from water prior to capillary electrophoresis detection. Preconcentration factors ranging between 36-44 were obtained for chloride, nitrate, perchlorate and sulfate, while a lower performance was observed for weaker acids as fluoride and phosphate (3-4). The limit of detection (LOD) was determined to be 0.16 μM, 0.18 μM and 0.18 μM for NO

Separation of Nile Blue-labelled fatty acids by CE with absorbance detection using a red light-emitting diode

Publisher: Wiley

Date: 04-2007

DOI: 10.1002/ELPS.200600580

Abstract: The separation of fatty acids derivatised with Nile Blue (NB) by CE with detection using a red light-emitting diode (LED) was examined. NB was selected as the derivatisation agent due to its high molar absorption coefficient of 76,000 M(-1) cm(-1) at 633 nm, making it well suited for sensitive absorbance detection using a red 635 nm LED. NB-labelled fatty acids were separated by both MEKC using SDS micelles, i-PrOH and n-BuOH and by NACE in a number of solvents including MeOH, EtOH and ACN. The sensitivity of NACE was superior to MEKC, with detection limits of 5x10(-7)-7x10(-7) M obtained for each acid, approximately 20 times lower than the MEKC method. The NACE detection limits are approximately 100 times lower than previous reports on the separation of fatty acids by CE using indirect absorbance detection, ten times lower than using indirect fluorescence detection and are inferior only to those obtained using precapillary derivatisation and direct fluorescence detection. The efficiency of the NACE method was also superior to MEKC and allowed the separation of unsaturated fatty acids to be examined, although it was not possible to baseline-resolve linoleic (C18:2) and linolenic (C18:3) acids in a reasonable time. The method was used to analyse the fatty acid profile of two edible oils, namely sunflower and sesame oils, after alkali hydrolysis, where it was possible to identify both the saturated and unsaturated fatty acids in each s le.

In‐Syringe Electrokinetic Protein Removal from Biological Samples prior to Electrospray Ionization Mass Spectrometry

Publisher: Wiley

Date: 13-10-2020

DOI: 10.1002/ANGE.202006481

Electroosmotic flow-balanced isotachophoretic stacking with continuous electrokinetic injection for the concentration of anions in high conductivity samples

Publisher: Elsevier BV

Date: 06-2010

DOI: 10.1016/J.CHROMA.2010.04.011

Abstract: An EOF counter-balanced ITP boundary has been used to stack anions from high conductivity s les during continuous electrokinetic injection of the s le. In a polystyrenesulfonate oly(diallyldimethylammonium chloride) polyelectrolyte coated capillary, the time at which the ITP boundary exited the capillary could be prolonged by balancing the movement of the boundary with the EOF. Using a bis-tris-propane electrolyte, the ITP boundary was removed from the capillary within 7min, while when using triethanolamine the ITP boundary was still at 30% of the capillary after 2h of injection. Using these systems, the sensitivity of a mixture of simple organic acids in 100mM Cl(-) was improved by 700-800-fold using bis-tris-propane with a whole-capillary injection of the s le and 5min of electrokinetic injection at +28kV, and 1100-1300-fold using triethanolamine and 60min of electrokinetic injection under the same conditions. The potential of the method to be applicable to high conductivity s les was demonstrated by stacking a whole capillary filled with urine spiked with naphthalenedisulfonic acid, with limits of detection 450 times lower than those achievable with a normal hydrodynamic injection.

Transient isotachophoresis-capillary zone electrophoresis with contactless conductivity and ultraviolet detection for the analysis of paralytic shellfish toxins in mussel samples

Publisher: Elsevier BV

Date: 10-2014

DOI: 10.1016/J.CHROMA.2014.08.074

Abstract: The accumulation of paralytic shellfish toxins (PSTs) in contaminated shellfish is a serious health risk making early detection important to improve shellfish safety and biotoxin management. Capillary electrophoresis (CE) has been proven as a high resolution separation technique compatible with miniaturization, making it an attractive choice in the development of portable instrumentation for early, on-site detection of PSTs. In this work, capillary zone electrophoresis (CZE) with capacitively coupled contactless conductivity detector (C(4)D) and UV detection were examined with counter-flow transient isotachophoresis (tITP) to improve the sensitivity and deal with the high conductivity s le matrix. The high sodium concentration in the s le was used as the leading ion while l-alanine was used as the terminating electrolyte (TE) and background electrolyte (BGE) in which the toxins were separated. Careful optimization of the injected s le volume and duration of the counter-flow resulted in limit of detections (LODs) ranging from 74.2 to 1020 ng/mL for tITP-CZE-C(4)D and 141 to 461 ng/mL for tITP-CZE-UV, an 8-97 fold reduction compared to conventional CZE. The LODs were adequate for the analysis of PSTs in shellfish s les close to the regulatory limit. Intra-day and inter-day repeatability values (percentage relative standard deviation, n=3) of tITP-CZE-C(4)D and tITP-CZE-UV methods for both migration time and peak height were in the range of 0.82-11% and 0.76-10%, respectively. The developed method was applied to the analysis of a contaminated mussel s le and validated against an Association of Official Analytical Chemists (AOAC)-approved method for PSTs analysis by high performance liquid chromatography (HPLC) with fluorescence detection (FLD) after pre-column oxidation of the s le. The method presented has potential for incorporation in to field-deployable devices for the early detection of PSTs on-site.

Photoinitiated polymerisation of monolithic stationary phases in polyimide coated capillaries using visible region LEDs

Publisher: Royal Society of Chemistry (RSC)

Date: 2008

DOI: 10.1039/B816958F

Abstract: The spatially controlled synthesis of poly(glycidyl methacrylate-co-ethylene dimethacrylate) monolithic stationary phases in polyimide coated fused silica capillaries by visible light induced radical polymerisation using a three-component initiator and a 660 nm light emitting diode (LED) as a light source is presented here.

Flow injection analysis of organic peroxide explosives using acid degradation and chemiluminescent detection of released hydrogen peroxide

Publisher: Elsevier BV

Date: 10-2015

DOI: 10.1016/J.TALANTA.2015.05.052

Abstract: The applicability of acid degradation of organic peroxides into hydrogen peroxide in a pneumatically driven flow injection system with chemiluminescence reaction with luminol and Cu(2+) as a catalyst (FIA-CL) was investigated for the fast and sensitive detection of organic peroxide explosives (OPEs). The target OPEs included hexamethylene triperoxide diamine (HMTD), triacetone triperoxide (TATP) and methylethyl ketone peroxide (MEKP). Under optimised conditions maximum degradations of 70% and 54% for TATP and HMTD, respectively were achieved at 162 µL min(-1), and 9% degradation for MEKP at 180 µL min(-1). Flow rates were precisely controlled in this single source pneumatic pressure driven multi-channel FIA system by model experiments on mixing of easily detectable component solutions. The linear range for detection of TATP, HMTD and H2O2 was 1-200 µM (r(2)=0.98-0.99) at both flow rates, while that for MEKP was 20-200 µM (r(2)=0.97) at 180 µL min(-1). The detection limits (LODs) obtained were 0.5 µM for TATP, HMTD and H2O2 and 10 µM for MEKP. The detection times varied from 1.5 to 3 min in this FIA-CL system. Whilst the LOD for H2O2 was comparable with those reported by other investigators, the LODs and analysis times for TATP and HMTD were superior, and significantly, this is the first time the detection of MEKP has been reported by FIA-CL.

Direct electrokinetic injection of inorganic cations from whole fruits and vegetables for capillary electrophoresis analysis

Publisher: Elsevier BV

Date: 2016

DOI: 10.1016/J.CHROMA.2015.08.012

Abstract: A novel approach for the direct injection from plant tissues without any s le pre-treatment has been developed by simply placing a small piece of the tissue into a capillary electrophoresis vial followed by application of a voltage for electrokinetic injection. Separations of sodium, potassium, calcium and magnesium were achieved using a BGE comprising 10mM imidazole and 2.5mM 18-crown-6-ether at pH 4.5. The addition of 2% (m/v) hydroxypropylmethyl cellulose to the separation buffer allowed for precise and accurate electrokinetic injection of ions from the plant material by halting the movement of tissue fluid into the capillary. This method provides both qualitative and quantitative data of inorganic cations, with quantitation in zucchini, mushroom and apple s les in agreement with Sector Field Inductively Coupled Plasma Mass Spectrometric analysis (r(2)=0.98, n=9). This method provides a new way for rapid, quantitative analysis by eliminating s le preparation procedures, and has great potential for a range of applications in plant science and food chemistry.

Comparing Microfluidic Performance of Three-Dimensional (3D) Printing Platforms

Publisher: American Chemical Society (ACS)

Date: 24-03-2017

DOI: 10.1021/ACS.ANALCHEM.7B00136

Abstract: Three-dimensional (3D) printing has emerged as a potential revolutionary technology for the fabrication of microfluidic devices. A direct experimental comparison of the three 3D printing technologies dominating microfluidics was conducted using a Y-junction microfluidic device, the design of which was optimized for each printer: fused deposition molding (FDM), Polyjet, and digital light processing stereolithography (DLP-SLA). Printer performance was evaluated in terms of feature size, accuracy, and suitability for mass manufacturing laminar flow was studied to assess their suitability for microfluidics. FDM was suitable for microfabrication with minimum features of 321 ± 5 μm, and rough surfaces of 10.97 μm. Microfluidic devices >500 μm, rapid mixing (71% ± 12% after 5 mm, 100 μL/min) was observed, indicating a strength in fabricating micromixers. Polyjet fabricated channels with a minimum size of 205 ± 13 μm, and a surface roughness of 0.99 μm. Compared with FDM, mixing decreased (27% ± 10%), but Polyjet printing is more suited for microfluidic applications where flow splitting is not required, such as cell culture or droplet generators. DLP-SLA fabricated a minimum channel size of 154 ± 10 μm, and 94 ± 7 μm for positive structures such as soft lithography templates, with a roughness of 0.35 μm. These results, in addition to low mixing (8% ± 1%), showed suitability for microfabrication, and microfluidic applications requiring precise control of flow. Through further discussion of the capabilities (and limitations) of these printers, we intend to provide guidance toward the selection of the 3D printing technology most suitable for specific microfluidic applications.

Determination of itraconazole and hydroxyitraconazole in human serum and plasma by micellar electrokinetic chromatography

Publisher: Elsevier BV

Date: 10-2003

DOI: 10.1016/S0021-9673(03)00573-9

Abstract: The electrokinetic separation of the hydrophobic antimycotic drug itraconazole (ITC) and its major metabolite, hydroxyitraconazole (HITC), by a binary aqueous-organic solvent medium containing sodium dodecylsulfate, by microemulsion electrokinetic chromatography (MEEKC) and by micellar electrokinetic chromatography (MEKC) was studied. The results suggest that the first approach is difficult to apply and that there is no substantial difference between separations performed using MEEKC and MEKC modified with n-butanol. The simpler MEKC method is more than adequate and was thus employed for the analysis of ITC and HITC in human serum and plasma. Separation was achieved in plain fused-silica capillaries having a low-pH buffer (pH 2.2) with sodium dodecyl sulfate micelles and reversed polarity. The addition of 2-propanol and n-butanol enhanced analyte solubility and altered the selectivity of the separation by influencing the magnitude of the electrophoretic component in the separation mechanism. Under optimised conditions and using head-column field- lified s le stacking, an internal standard, ITC and two forms of HITC could be separated in under 9 min, with detection limits less than 0.01 microg/mL. Analysis of s les from patients currently prescribed ITC revealed a different HITC peak area ratio to that of the standards, suggesting a stereoselective component of ITC metabolisation. Comparison of MEKC data with those of a HPLC method employed on a routine basis showed excellent agreement, indicating the potential of this approach for therapeutic drug monitoring of ITC.

Manufacturing and application of a fully polymeric electrophoresis chip with integrated polyaniline electrodes

Publisher: Royal Society of Chemistry (RSC)

Date: 2010

DOI: 10.1039/C003333B

Abstract: This work describes the development of a fully polymeric microchip with integrated polymeric electrodes suitable for performing microchip electrophoresis. The polymer electrodes were fabricated in a thin film of the conducting polymer, polyaniline (PANI), by flash lithography using a studio camera flash and a transparency mask. During flash welding, exposed regions welded into non-conducting regions forming a conducting polymer circuit in the non-exposed regions. Using a structured layer of dry film photoresist for sealing, a polydimethylsiloxane (PDMS) substrate containing channels and reservoirs was bound to the PANI film to form an integrated microfluidic device. The conducting regions of the PANI film were shown to be capable of carrying the high voltages of up to 2000 V required for chip electrophoresis, and were stable for up to 30 minutes under these conditions. The PANI electrodes were used for the electrophoretic separation of three sugars labelled with 8-amino-1,3,6-pyrenetrisulfonic acid (APTS) in the dry film resist-PDMS hybrid device. Highly efficient separations comparable to those achieved in similar microchips using platinum electrodes confirm the potential of polyaniline as a new material suitable for high voltage electrodes in Lab-on-a-chip devices.

Determination of inorganic anions by capillary electrochromatography

Publisher: Elsevier BV

Date: 06-2001

DOI: 10.1016/S0165-9936(01)00073-5

Pressure-assisted electrokinetic supercharging for the enhancement of non-steroidal anti-inflammatory drugs

Publisher: Elsevier BV

Date: 09-2011

DOI: 10.1016/J.CHROMA.2011.07.044

Abstract: Electrokinetic supercharging (EKS) combines field- lified s le injection with transient isotachophoresis (tITP) to create a powerful on-line preconcentration technique for capillary electrophoresis. In this work, EKS is enhanced with a positive pressure (pressure-assisted EKS, or PA-EKS) during injection to improve stacking of non-steroidal anti-inflammatory drugs (NSAIDs). Several parameters, including buffer composition and concentration, terminating electrolyte, organic modifier, and injection voltage and injection time of both terminating electrolyte and s le were optimized. Detection limits for seven NSAIDs were determined and an enhancement in sensitivity of almost 50,000-fold was obtained. The PA-EKS method has the potential to be a simple MS compatible preconcentration method to improve the sensitivity of CE.

Isotachophoresis for rapid transformation of Escherichia coli

Publisher: Wiley

Date: 21-12-2022

DOI: 10.1002/ELPS.202100095

Abstract: A frequent limitation of electroporation (EP) and chemical transformation (CT) are the need of tedious and time‐consuming procedures for inducing transformation competence, the substantial number of cells required, and the low transformation yields typically achieved. Here, we show a new and rapid electrokinetic method for transformation of small number of noncompetent Escherichia coli TOP10 cells (2–3 × 10 5 ) at room temperature. Escherichia coli TOP10 cells and plasmid DNA are sequentially injected into a 50 μm ID capillary and focused into 11.5 nL by isotachophoresis (ITP) induced by application of high DC voltage (–16 kV). Through ITP, a large excess of plasmid DNA is brought in contact with the cell surface, with the contact time adjusted by application of a counter‐pressure (1.3 psi) opposing the ITP movement. The transformation rate was more than 1000‐fold higher compared to EP and CT at survival rates greater than 60%.

Time-Resolved Pharmacological Studies using Automated, On-line Monitoring of Five Parallel Suspension Cultures

Publisher: Springer Science and Business Media LLC

Date: 04-09-2017

DOI: 10.1038/S41598-017-10472-1

Abstract: Early stage pharmacological studies rely on in vitro methodologies for screening and testing compounds. Conventional assays based on endpoint measurements provide limited information because the lack in temporal resolution may not determine the pharmacological effect at its maximum. We developed an on-line, automated system for near real-time monitoring of extracellular content from five parallel suspension cultures, combining cell density measurements with a high-resolution separations every 12 minutes for 4 days. Selector and switching valves provide the fluidic control required to s le from one culture during the analysis of the previous s le from another culture, a time-saving measure that is fundamental to the throughput of the presented system. The system was applied to study the metabolic effects of the drugs rotenone, β-lapachone and clioquinol using lactate as metabolic indicator. For each drug, 96 assays were executed on the extracellular matrix at three concentrations with two controls in parallel, consuming only 5.78 mL of media from each culture over four days, less than 60 μL per analysis. The automated system provides high s le throughput, good temporal resolution and low s le consumption combined with a rugged analytical method with adequate sensitivity, providing a promising new platform for pharmacological and biotechnological studies.

Evaluation of Peakmaster for computer‐aided multivariate optimisation of a CE separation of 17 antipsychotic drugs using minimal experimental data

Publisher: Wiley

Date: 03-2009

DOI: 10.1002/ELPS.200800532

Abstract: The computer-assisted development of a CE method for compliance monitoring of a group of 17 antipsychotic drugs (chlorpromazine hydrochloride, clozapine, droperidol, flupenthixol dihydrochloride, fluphenazine dihydrochloride, haloperidol, pimozide, thioridazine hydrochloride, trifluoperazine dihydrochloride, prochlorperazine dimaleate, amisulpride, aripiprazole, olanzapine, quetiapine fumarate, risperidone, ziprasidone, and zuclopenthixol dihydrochloride) was performed. Peakmaster, a free simulation program for CE, was employed in a multivariate optimisation approach to determine suitable BGE conditions with minimal experimentation. However, analyte input parameters (pK(a) and limiting ionic mobility) were not included within the software and required determination. Limiting ionic mobility was determined experimentally, while pK(a) values were calculated using ACD Labs software. A modified chromatographic response factor, which identified the BGE providing the greatest resolution between each pair of peaks within 10 min, was used and determined a pH 2.5 and an ionic strength of 50 mM as optimal. Marked disparities were apparent between experimentally determined and computer-simulated results, due to error associated with pK(a) values calculated using ACD Labs. These results confirm that Peakmaster analyses are highly sensitive to pK(a) values, especially where the pH of the BGE is in the proximity of the analyte pK(a) but also that Peakmaster does allows a rational approach to dramatically reduce the amount of experimental work required for multivariate optimisation of conditions for CE.

Stalk cell polar ion transport provide for bladder‐based salinity tolerance in Chenopodium quinoa

Publisher: Wiley

Date: 06-2022

DOI: 10.1111/NPH.18205

Abstract: Chenopodium quinoa uses epidermal bladder cells (EBCs) to sequester excess salt. Each EBC complex consists of a leaf epidermal cell, a stalk cell, and the bladder. Under salt stress, sodium (Na + ), chloride (Cl − ), potassium (K + ) and various metabolites are shuttled from the leaf lamina to the bladders. Stalk cells operate as both a selectivity filter and a flux controller. In line with the nature of a transfer cell, advanced transmission electron tomography, electrophysiology, and fluorescent tracer flux studies revealed the stalk cell’s polar organization and bladder‐directed solute flow. RNA sequencing and cluster analysis revealed the gene expression profiles of the stalk cells. Among the stalk cell enriched genes, ion channels and carriers as well as sugar transporters were most pronounced. Based on their electrophysiological fingerprint and thermodynamic considerations, a model for stalk cell transcellular transport was derived.

Non-aqueous capillary electrophoresis with red light emitting diode absorbance detection for the analysis of basic dyes

Publisher: Elsevier BV

Date: 11-2006

DOI: 10.1016/J.ACA.2006.07.066

Abstract: Non-aqueous capillary electrophoresis was evaluated for the separation of five hydrophobic basic blue dyes for application in forensic dye analysis. The use of a red light emitting diode as a high intensity, low-noise light source provided sensitive detection of the blue dyes while also allowing the evaluation of solvents that absorb strongly in the UV region. Excellent peak shapes and separation selectivity were obtained in methanol, ethanol, acetonitrile and dimethylsulfoxide, however water, tetrahydrofuran, dimethylformamide and acetone were unsuitable as solvents due to poor peak shapes and a lack of sensitivity, most likely due to adsorption onto the capillary wall. Due to the known compatibility of methanol with capillary electrophoresis-mass spectrometry, this solvent was examined further with the relative acidity/basicity of the electrolyte being optimised with an artificial neural network. The optimised method was examined for the separation of ink s les from 6 fibre tip and 2 ball point blue or black pens and showed that a unique migration time for the main dye component in seven of the eight pens could be obtained.

Analysis of flavonoids by capillary zone electrophoresis with electrokinetic supercharging

Publisher: Royal Society of Chemistry (RSC)

Date: 2011

DOI: 10.1039/C1AN15277G

Abstract: On-line concentration via Electrokinetic Supercharging (EKS) was used to enhance the sensitivity of the capillary electrophoretic separation of the four flavonoids naringenin, hesperetin, naringin and hesperidin. Separation conditions, including the background electrolyte pH and concentration, the length and choice of terminator and the electrokinetic injection time were optimized. The optimum conditions were: a background electrolyte of 30 mM sodium tetraborate (pH 9.5) containing 5% (v/v) of methanol, electrokinetic injection of the s le (130 s, -10 kV) followed by hydrodynamic injecting of 100 mM 2-(cyclohexylamino)ethanesulfonic acid (CHES) (17 s, 0.5 psi) as terminator, and separation with -20 kV. Under these conditions the four flavonoids could be separated with a s le-to-s le time of 15 min and detection limits from 2.0 to 6.8 ng mL(-1). When compared to a conventional hydrodynamic injection the sensitivity was enhanced between 824 and 1515 times which is 7.6-16 times higher than other CE methods for the on-line concentration of flavonoids. The applicability of the developed method was demonstrated by the detection of the four flavonoids in an aqueous extract of Clematis hexapetala pall.

Recent trends in capillary and micro-chip electrophoretic instrumentation for field-analysis

Publisher: Elsevier BV

Date: 04-2018

DOI: 10.1016/J.TEAC.2018.03.001

Low-Cost Passive Sampling Device with Integrated Porous Membrane Produced Using Multimaterial 3D Printing

Publisher: American Chemical Society (ACS)

Date: 17-09-2018

DOI: 10.1021/ACS.ANALCHEM.8B02893

Abstract: Multimaterial 3D printing facilitates the rapid production of complex devices with integrated materials of varying properties and functionality. Herein, multimaterial fused deposition modeling (MM-FDM) 3D printing was applied to the fabrication of low-cost passive s ler devices with integrated porous membranes. Using MM-FDM 3D printing, the device body was produced using black polylactic acid, with Poro-Lay Lay-Felt filament used for the printing of the integrated porous membranes (rubber-elastomeric polymer, porous after removal of a water-soluble poly(vinyl alcohol) component). The resulting device consisted of two interlocking circular frames, each containing the integrated membrane, which could be efficiently sealed together without the need for additional O-rings, and prevented loss of enclosed microparticulate sorbent. Scanning electron microscopy (SEM) analysis of the purified composite filament confirmed the porous properties of the material, an average pore size of ∼30 nm. The printed passive s lers with various membrane thicknesses, including 0.5, 1.0, and 1.5 mm, were evaluated for their ability to facilitate the extraction of atrazine as the model solute onto the internal sorbent, under standard conditions. Gas chromatography-mass spectrometry was used to determine the uptake of atrazine by the device from standard water s les and also to evaluate any chemical leaching from the printed materials. The s ler with 0.5 mm thick membrane showed the best performance with 87% depletion and a s ling rate of 0.19 Ld

Capillary electrophoresis for monitoring bioprocesses

Publisher: Wiley

Date: 08-05-2013

DOI: 10.1002/ELPS.201200646

Abstract: Chemical characterization and monitoring of fermentation broths and cell culture media provide significant information on the changes occurring within these complex and dynamic systems. Analytical methods based on CE in capillaries and microchips are attractive for integration in instrumental tools to obtain this critical data, improving the understanding and control of bioprocesses. In this review, the use of CE for chemical characterization and monitoring fermentations is discussed, organized by analyte class, including organic acids, pharmaceuticals, proteins, sugars, amino acids, and metabolites published between 1992 and October 2012. A section is dedicated to the roles CE plays throughout the wine making process, where applications range from characterization and increase in fundamental understanding of the fermentation to forensic applications, verifying the authenticity of the wine.

Light-emitting diode-compatible probes for indirect detection of anions in CE

Publisher: Wiley

Date: 10-2007

DOI: 10.1002/ELPS.200600809

Abstract: A range of compounds were evaluated as probes for the indirect detection of inorganic ions using CE and light-emitting diodes (LEDs) as the light source. Emphasis was placed on examining probes likely to absorb strongly in the UV-Vis region near 350-430 nm as compounds, which absorb at longer wavelengths tend to be bulkier and adsorb onto the capillary wall. These probes should act as a replacement for the very effective but carcinogenic probe chromate. Two probes were identified and evaluated: p-nitrophenol and 4-hydroxy-3,5-dinitrobenzoic acid. The former showed the most potential with low-mobility anions, while the later had a moderate electrophoretic mobility and was more suitable for a wider mobility range of analytes. However, neither could match the efficiencies and LOD of chromate for the separation of the fast inorganic ions such as chloride, nitrate and sulphate. Nevertheless, application of the 4-hydroxy-3,5-dinitrobenzoic acid system to the determination of oxalate in Bayer liquors showed excellent sensitivity and selectivity.

Erratum to “Ion chromatography on-chip”

Publisher: Elsevier BV

Date: 2002

DOI: 10.1016/S0021-9673(01)01461-3

Electrophoretic separations on paper: Past, present, and future-A review

Publisher: Elsevier BV

Date: 09-2017

DOI: 10.1016/J.ACA.2017.06.015

Abstract: Point-of-collection (POC) devices aim for a fast, on-site detection for medical and environmental purposes. In this area, microfluidic Paper-based Analytical Devices (μPADs) have recently gained popularity because these are potentially cheap and environmentally friendly to produce, and easy to use. From an analytical perspective, paper is well known for its use as a substrate for chromatography, but less known for its use in electrophoretic separations. With the recent interest in μPADs, most applications are based on rather simple assays with relatively few applications incorporating an analytical separation. The focus of this review is on paper-based electrophoresis, originating with the key developments in the 1940s and 1950s as well as the recent developments of electrophoretic μPADs, and concluding with a critical discussion of the opportunities and challenges for electrophoretic μPADS in the future.

Sieving polymer synthesis by reversible addition fragmentation chain transfer polymerization

Publisher: Wiley

Date: 08-11-2013

DOI: 10.1002/ELPS.201300288

Abstract: Replaceable sieving polymers are the fundamental component for high resolution nucleic acids separation in CE. The choice of polymer and its physical properties play significant roles in influencing separation performance. Recently, reversible addition fragmentation chain transfer (RAFT) polymerization has been shown to be a versatile polymerization technique capable of yielding well defined polymers previously unattainable by conventional free radical polymerization. In this study, a high molecular weight PDMA at 765 000 gmol-1 with a PDI of 1.55 was successfully synthesized with the use of chain transfer agent - 2-propionic acidyl butyl trithiocarbonate (PABTC) in a multi-step sequential RAFT polymerization approach. This study represents the first demonstration of RAFT polymerization for synthesizing polymers with the molecular weight range suitable for high resolution DNA separation in sieving electrophoresis. Adjustment of pH in the reaction was found to be crucial for the successful RAFT polymerization of high molecular weight polymer as the buffered condition minimizes the effect of hydrolysis and aminolysis commonly associated with trithiocarbonate chain transfer agents. The separation efficiency of PABTC-PDMA was found to have marginally superior separation performance compared to a commercial PDMA formulation, POP™-CAP, of similar molecular weight range.

Lab on a chip for point-of-care analysis of drugs in body fluids

Publisher: Institution of Engineering and Technology

Date: 19-07-2016

DOI: 10.1049/PBHE001E_CH20

Insight into the mechanism of transient trapping in micellar electrokinetic chromatography

Publisher: Wiley

Date: 02-2011

DOI: 10.1002/ELPS.201000547

Abstract: Transient trapping is a new mechanism of on-line s le concentration and separation that has recently been presented. It involves the injection of a short length of micellar solution in front of the s le, making it similar to sweeping in partial-filling MEKC. Here, we examine the mechanism of transient trapping by the use of computer simulations and compare it to sweeping in MEKC for the two analytes, sulforhodamine B and 101. The simulation results confirm the mechanism for concentration and separation originally proposed. The mechanism for concentration is similar to sweeping since the analytes are picked and accumulated by the micelles that penetrate the s le zone. The mechanism for separation is however quite unique since the concentrated analytes are trapped for a few seconds on the s le/micelle boundary before they are released as the concentration of micelle is reduced as it undergoes electromigration dispersion and the analytes separate down a micelle gradient. Simulation results suggested that a significant contribution of band broadening arises from the micelle gradient, with shallower gradients resulting in broader peaks. However, this is offset by an increase in selectivity, such that resolution was enhanced even though the peaks are broader. Transient trapping analysis with similar resolution to those obtained by sweeping MEKC could be achieved in 1/10 of the time and 1/4 of the capillary length, which results in a 2-3 times increase in sensitivity.

Enhanced physicochemical properties of polydimethylsiloxane based microfluidic devices and thin films by incorporating synthetic micro-diamond

Publisher: Springer Science and Business Media LLC

Date: 08-11-2017

DOI: 10.1038/S41598-017-15408-3

Abstract: Synthetic micro-diamond-polydimethylsiloxane (PDMS) composite microfluidic chips and thin films were produced using indirect 3D printing and spin coating fabrication techniques. Microfluidic chips containing up to 60 wt% micro-diamond were successfully cast and bonded. Physicochemical properties, including the dispersion pattern, hydrophobicity, chemical structure, elasticity and thermal characteristics of both chip and films were investigated. Scanning electron microscopy indicated that the micro-diamond particles were embedded and interconnected within the bulk material of the cast microfluidic chip, whereas in the case of thin films their increased presence at the polymer surface resulted in a reduced hydrophobicity of the composite. The elastic modulus increased from 1.28 for a PDMS control, to 4.42 MPa for the 60 wt% composite, along with a three-fold increase in thermal conductivity, from 0.15 to 0.45 W m −1 K −1 . Within the fluidic chips, micro-diamond incorporation enhanced heat dissipation by efficient transfer of heat from within the channels to the surrounding substrate. At a flow rate of 1000 μL/min, the gradient achieved for the 60 wt% composite chip equalled a 9.8 °C drop across a 3 cm long channel, more than twice that observed with the PDMS control chip.

Stainless Steel Pinholes for Fast Fabrication of High-Performance Microchip Electrophoresis Devices by CO₂ Laser Ablation

Publisher: American Chemical Society (ACS)

Date: 15-10-2013

DOI: 10.1021/AC402631G

Abstract: With the introduction of hobby laser engravers/cutters, the use of CO2 laser micromachining on poly(methyl methacrylate) (PMMA) has the potential for flexible, low cost, rapid prototyping of microfluidic devices. Unfortunately, the feature size created by most entry-level CO2 laser micromachining systems is too large to become a functional tool in analytical microfluidics. In this paper, we report a novel method to reduce the feature size of microchannels and the bulges formed at the rim of the channel during CO2 laser micromachining by passing the laser beam through a stainless steel pinhole. Without the pinhole, the channel width was typically 300 μm wide. However, when 50 or 35 μm diameter pinholes were used, channel widths of 60 and 25 μm, respectively, could be obtained. The height of the bulge deposited directly next to the channel was reduced to less than 0.8 μm with the pinhole during ablation. Separations of fluorescent dyes on devices ablated with and without the pinhole were compared. On devices fabricated with the pinhole, the number of theoretical plates/m was 2.2-fold higher compared to devices fabricated without the pinhole, and efficiencies comparable to embossed PMMA and laser ablated glass chips were obtained. A mass-produced commercial hobby laser (retailing at ∼$2500), when equipped with a $500 pinhole, represents a rapid and low-cost approach to the rapid fabrication of rigid plastic microchips including the narrow microchannels required for microchip electrophoresis.

Electrokinetic supercharging‐electrospray ionisation‐mass spectrometry for separation and on‐line preconcentration of hypolipidaemic drugs in water samples

Publisher: Wiley

Date: 26-03-2010

DOI: 10.1002/ELPS.200900420

Abstract: Electrokinetic supercharging, a powerful on‐line preconcentration technique in CE, was for the first time hyphenated with ESI‐MS for the on‐line concentration and separation of five hypolipidaemic drugs. The electrophoretic separation was performed in a co‐EOF mode using the EOF reversal agent, hexadimethrine bromide, in ammonium bicarbonate electrolyte, pH 9.00. The ionic strength and the amount of methanol in the buffer were optimised in a multivariate manner using artificial neural networks, with the optimal conditions being 60 mM ammonium bicarbonate containing 60% methanol, providing baseline resolution of the five hypolipidaemics within 20 min. Using electrokinetic supercharging, the sensitivity of the method was improved 1000‐fold over a conventional injection under field‐ lified s le stacking conditions with LODs of 180 ng/L. This is the first report of the separation of hypolipidaemics by CE. The developed method was validated and then applied to the determination of the target drugs in water s les from Hobart city.

LED controlled flow photolysis for concentration gradients in microfluidic systems

Publisher: Royal Society of Chemistry (RSC)

Date: 2010

DOI: 10.1039/C000258E

Abstract: Many of the channels and reservoirs in microfluidic systems are used simply to allow liquids with different compositions to be delivered to where they are needed. An alternative approach is to use dissolved photochemicals and variable intensity LEDs to generate composition changes in situ. We applied this approach to generate concentration gradients of HCl for gradient ion chromatography.

Multimaterial 3D Printed Fluidic Device for Measuring Pharmaceuticals in Biological Fluids

Publisher: American Chemical Society (ACS)

Date: 04-12-2018

DOI: 10.1021/ACS.ANALCHEM.8B03772

Abstract: Multimaterial 3D printing provides a unique capability for the creation of highly complex integrated devices where complementary functionality is realized using differences in material properties. Using a single and automated print process, microfluidic devices were fabricated containing (i) an optically transparent structure for fluorescence detection, (ii) electrodes for electrokinetic transport, (iii) a primary membrane to remove particulates and macromolecules including proteins, and (iv) a secondary membrane to concentrate small molecule targets. The device was used for the simultaneous extraction and concentration of small molecule pharmaceuticals from urine, which was followed by an on-chip electrophoretic separation of the concentrated targets for quantitative analysis. Owing to the high level of functional integration inside the device, manual handling was minimal and restricted to the introduction of the s le and buffer solutions. The 3D printed s le-in/answer-out device allowed the direct quantification of icillin-a small molecule pharmaceutical-in untreated urine within 3 min, down to 2 ppm. These results demonstrate the potential of 3D printing for on-demand fabrication of disposable, functionally integrated devices for low-cost point-of-collection (POC) diagnostics.

A rapid quantitative determination of phenolic acids in Brassica oleracea by capillary zone electrophoresis

Publisher: Elsevier BV

Date: 07-2011

DOI: 10.1016/J.FOODCHEM.2011.01.015

Abstract: A simple and rapid capillary zone electrophoresis method to quantitatively determine the phenolic acid contents in brassica vegetables is described. Phenolic compounds were extracted from broccoli, broccolini, Brussels sprouts, cabbage and cauliflower and the main hydroxycinnamic acids (sinapic, ferulic, p-coumaric and caffeic acids) were isolated by solid phase extraction with C18 cartridges. Using an optimised method, the four analytes were separated in less than 7min in a 50μm×60cm capillary with a 15mM borate buffer (pH=9.13) and a separation voltage of 30kV at 30°C. A linear relationship was observed for the method (r=0.9997-0.9999) with detection limits ranging from 1.1 to 2.3mg/kg of vegetables for the analytes. This method demonstrated good reproducibility with coefficients of variation of less than 5% for peak area and less than 1% for migration time (n=7). The method was successfully applied to quantitatively determine the phenolic acid contents in a range of brassica vegetables and the results were in good agreement when compared to those from high performance liquid chromatography analysis.

Quantitative determination of glucoraphanin in Brassica vegetables by micellar electrokinetic capillary chromatography

Publisher: Elsevier BV

Date: 03-2010

DOI: 10.1016/J.ACA.2010.01.043

Abstract: Glucoraphanin, a glucosinolate, is found naturally in plants and is present in relatively high concentrations in broccoli. Glucosinolates have received much attention as studies have indicated that a diet rich in them may provide some protection from certain cancers. A micellar electrokinetic chromatography (MEKC) method using sodium cholate as the micellar phase has been developed to quantify for glucoraphanin in broccoli (seeds and florets) and Brussels sprouts. The glucoraphanin peak elutes just under 5min with a theoretical plate number of 380,000 per metre of capillary. The method is suitable for crude extracts of broccoli and Brussels sprouts. Glucoraphanin in broccoli seeds (1330mg/100g) broccoli florets (89mg/100g) and Brussels sprouts (3mg/100g) was determined and agreed with the data obtained by high performance liquid chromatography. The LODs were 10-100 times below the levels typically found in broccoli seeds (4mg/100g), broccoli florets (0.9mg/100g) and Brussels sprouts (0.1mg/100g).

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

Portable capillary electrophoresis coupled with swab-based extraction device for cleaning validation in pharmaceutical facilities

Publisher: Elsevier BV

Date: 2023

DOI: 10.1016/J.CHROMA.2022.463666

Fast analysis of phenolic acids by electrokinetic supercharging‐nonaqueous capillary electrophoresis

Publisher: Wiley

Date: 07-2010

DOI: 10.1002/JSSC.201000090

Abstract: A method was developed to analyze phenolic acids by nonaqueous CE after online concentration with electrokinetic supercharging. The EOF was reversed using a polyelectrolyte multilayer approach based on the successive adsorption of poly(diallyldimethylamonium chloride) and poly(styrenesulfonate) to reduce the analysis time. The results showed that the coatings were stable during 40 consecutive injections. Four phenolic acids were separated within 8 min using 30 mM ammonium acetate (pH* 8.0). The electrokinetic injection time and terminator length of the electrokinetic supercharging method were optimized to improve the detection sensitivity. Under the optimized conditions (electrokinetic injection of 100 s, -10 kV terminator of 20 mM 2-(cyclohexylamino) ethanesulfonic acid, 22 s, 0.5 psi), the sensitivity was enhanced from 300- to 440-fold. The detection limits, based on three times noise, were in the range 1.0-2.5 ng/mL.

Thiol‐yne 3D Printable Polymeric Resins for the Efficient Removal of a Model Pollutant from Waters

Publisher: Wiley

Date: 27-10-2023

DOI: 10.1002/MAME.202200497

Abstract: A new 3D printable resin formulation is developed and optimized from commercially available thiol (pentaerythritol tetrakis(3‐mercaptopropionate) PETMP) and alkyne (3‐butyn‐1‐ol BA) monomers. Printed objects are characterized by Fourier‐transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The extraction efficiency of the printed thiol‐yne device is then investigated using a model dye – malachite green (MG). The results displayed excellent dye removal efficiency with 95% MG removed within 5 min. The 3D‐printed devices are reusable and show 100% removal over six cycles after washing with deionized water and methanol. The presence of surface hydroxyl groups derived from the BA monomer is shown to enhance dye adsorption in comparison to control materials. The printing procedure and resin formulation are robust and consistent when devices from different resin batches are compared for MG dye removal. The thiol‐yne 3D printed devices demonstrated excellent dye removal ( 99%) from water s les collected from a tap and a nearby river source. The successful development of this resin provides a new thiol‐yne‐based resin system for stereolithography (SLA) 3D printing for the removal of organic dyes from wastewater and presents a potential for broad applications in water treatment.

Maskless photolithography using UV LEDs

Publisher: Royal Society of Chemistry (RSC)

Date: 2008

DOI: 10.1039/B800465J

Abstract: A UV light emitting diode (LED) with a maximum output of 372 nm was collimated using a pinhole and a small plastic tube and focused using a microscope objective onto a substrate for direct lithographic patterning of the photoresist. Movement of the substrate with a motorised linear stage (syringe pump) allowed lines in SU-8 to be pattered with a width down to 35 microm at a linear velocity of 80 microm s(-1), while in the dry film resist Ordyl SY 330, features as narrow as 17 microm were made at a linear velocity of 245 microm s(-1). At this linear velocity, a 75 mm long feature could be patterned in 5 min. Functional microfluidic devices were made by casting PDMS on a master made by LED lithography. The results show that UV LEDs are a suitable light source for direct writing lithography, offering a budget friendly, and high resolution alternative for rapid prototyping of features smaller than 20 microm.

Analysis of flavonoids by non-aqueous capillary electrophoresis with 1-ethyl-3-methylimidazolium ionic-liquids as background electrolytes

Publisher: Elsevier BV

Date: 12-2013

DOI: 10.1016/J.CHROMA.2013.10.014

Abstract: The separation of three flavonoids, kaempferol, quercetin and luteolin, by capillary zone electrophoresis with three 1-ethyl-3-methylimidazolium ionic liquids (ILs), namely chloride, hydrogen sulfate and tetrafluoroborate salts, under non-aqueous conditions using acetonitrile as solvent was investigated. Depending on the IL, the three flavonoids can be separated under positive voltage with a low IL concentration and negative voltage with a high IL concentration. The separations are based on heteroconjungation between the IL anions and the analytes. The heteroconjungation between the anions of the ILs and the analytes is proton sensitive and only a very small amount of protic solvents, such as methanol, added into the electrolyte solution can harm the separation, but higher IL concentrations can overcome this higher amount of protic solvents. Using a high concentration of IL in the s le was used to enhance the flavonoid solubility by as much as 10, overcoming the problem of the low solubility during NACE analysis with ACN as the solvent. Finally, kaempferol, quercetin and luteolin in Semen Plantaginis were analysed by nonaqueous capillary electrophoresis with low concentration of the hydrogen sulfate ionic liquid with excellent results.

On-line simultaneous and rapid separation of anions and cations from a single sample using dual-capillary sequential injection-capillary electrophoresis

Publisher: Elsevier BV

Date: 06-2013

DOI: 10.1016/J.ACA.2013.03.027

Abstract: A novel capillary electrophoresis (CE) approach has been developed for the simultaneous rapid separation and identification of common environmental inorganic anions and cations from a single s le injection. The method utilised a sequential injection-capillary electrophoresis instrument (SI-CE) with capacitively-coupled contactless conductivity detection (C(4)D) constructed in-house from commercial-off-the-shelf components. Oppositely charged analytes from a single s le plug were simultaneously injected electrokinetically onto two separate capillaries for independent separation and detection. Injection was automated and may occur from a syringe or be directly coupled to an external source in a continuous manner. Software control enabled high s le throughput (17 runs per hour for the target analyte set) and the inclusion of an isolation valve allowed the separation capillaries to be flushed, increasing throughput by removing slow migrating species as well as improving repeatability. Various environmental and industrial s les (subjected only to filtering) were analysed in the laboratory with a 3 min analysis time which allowed the separation of 23 inorganic and small organic anions and cations. Finally, the system was applied to an extended automated analysis of Hobart Southern Water tap water for a period of 48 h. The overall repeatability of the migration times of a 14 analyte standard s le was less than 0.74% under laboratory conditions. LODs ranged from 5 to 61 μg L(-1). The combination of automation, high confidence of peak identification, and low limits of detection make this a useful system for the simultaneous identification of a range of common inorganic anions and cations for discrete or continuous monitoring applications.

Electrokinetic Size and Mobility Traps for On-site Therapeutic Drug Monitoring

Publisher: Wiley

Date: 04-05-2015

DOI: 10.1002/ANIE.201501794

Abstract: The extraction of target analytes from biological s les is a bottleneck in analysis. A microfluidic device featuring an electrokinetic size and mobility trap was formed by two nanojunctions of different pore size to extract and concentrate analytical targets from complex s les. The trap was seamlessly coupled with electrophoretic separation for quantitative analysis. The device was applied to the analysis of icillin levels in blood within 5 min and a linear response over the range of 2.5-20 μg mL(-1). This covers the recommended levels for treating sepsis, a critical condition with 30 to 50% mortality and unpredicted drug levels. The device provides a new opportunity for on-site therapeutic drug monitoring, which should enable quick and accurate dosing and may save lives in such critical conditions.

3D printed LED based on-capillary detector housing with integrated slit

Publisher: Elsevier BV

Date: 05-2017

DOI: 10.1016/J.ACA.2017.02.020

Abstract: A 3D printed photometric detector body with integrated slit was fabricated to position a LED and photodiode either side of capillary tubing using a fused deposition modelling (FDM) printer. To make this approach suitable for capillaries down to 50 μm i.d. the dimension of the in-built slit is the critical element of the printed housing. The spatial orientation of the model for printing was found to significantly impact on the resolution of the structures and voids that can be printed. By designing a housing with a slit positioned in the XY plane in parallel with the print direction, the narrowest void (slit) that could be printed was 70 μm. The potential use of the 3D printed slit for photometric detection was characterised using tubing and capillary from 500 down to 50 μm i.d, demonstrating a linear response from 632 to 40 mAU. The effective pathlength and stray light varied from 383 to 22 μm and 3.8% - 50% for 500- 50 μm i.d tubing and capillary. The use of a V-shaped alignment feature allowed for easy and reliable positioning of the tubing inside the detector, as demonstrated by a RSD of 1.9% (n = 10) in peak height when repositioning the tubing between measurements using flow injection analysis (FIA). The performance of the 3D printed housing and 70 μm slit was benchmarked against a commercially available interface using the CE separation of Zn

Microfluidic isotachophoresis: A review

Publisher: Wiley

Date: 14-05-2013

DOI: 10.1002/ELPS.201300021

Abstract: Electromigration methods including CE and ITP are attractive for incorporation in microfluidic devices because they are relatively easily adaptable to miniaturization. After its popularity in the 1970s, ITP has made a comeback in microfluidic format (μ-ITP, micro-ITP) driven by the advantages of the steady-state boundary, the self-focusing effect, and the ability to aid in preconcentrating analytes in the s le while removing matrix components. In this review, we provide an overview of the developments in the area of μ-ITP in a context of the historic developments with a focus on recent developments in experimental and computational ITP and discuss possible future trends. The chip-ITP areas and topics discussed in this review and the corresponding sections include: PC simulations and modeling, analytical μ-ITP, preconcentration ITP, transient ITP, peak mode ITP, gradient elution ITP, and free-flow ITP, while the conclusions provide a critical summary and outlook. The review also contains experimental conditions for μ-ITP applications to real-world s les from over 50 original journal publications.

Ion transport in broad bean leaf mesophyll under saline conditions

Publisher: Springer Science and Business Media LLC

Date: 22-07-2014

DOI: 10.1007/S00425-014-2117-Z

Abstract: Salt stress reduces the ability of mesophyll tissue to respond to light. Potassium outward rectifying channels are responsible for 84 % of Na (+) induced potassium efflux from mesophyll cells. Modulation in ion transport of broad bean (Vicia faba L.) mesophyll to light under increased apoplastic salinity stress was investigated using vibrating ion-selective microelectrodes (the MIFE technique). Increased apoplastic Na(+) significantly affected mesophyll cells ability to respond to light by modulating ion transport across their membranes. Elevated apoplastic Na(+) also induced a significant K(+) efflux from mesophyll tissue. This efflux was mediated predominately by potassium outward rectifying channels (84 %) and the remainder of the efflux was through non-selective cation channels. NaCl treatment resulted in a reduction in photosystem II efficiency in a dose- and time-dependent manner. In particular, reductions in Fv'/Fm' were linked to K(+) homeostasis in the mesophyll tissue. Increased apoplastic Na(+) concentrations induced vanadate-sensitive net H(+) efflux, presumably mediated by the plasma membrane H(+)-ATPase. It is concluded that the observed pump's activation is essential for the maintenance of membrane potential and ion homeostasis in the cytoplasm of mesophyll under salt stress.

Editorial

Publisher: Elsevier BV

Date: 12-2008

DOI: 10.1016/J.CHROMA.2008.10.044

Silica nanoparticle-templated methacrylic acid monoliths for in-line solid-phase extraction–capillary electrophoresis of basic analytes

Publisher: Elsevier BV

Date: 06-2009

DOI: 10.1016/J.CHROMA.2009.04.012

Abstract: Polymeric ion-exchange monoliths typically exhibit low capacities due to the limited surface area on the globules of the monoliths. The ion-exchange binding of protonated weakly basic analytes on deprotonated carboxylate sites on methacrylate polymer monoliths has been increased by templating the monoliths with silica nanoparticles. The templating method is achieved by adding the nanoparticles as a suspension to the polymerisation mixture. After polymerisation, the nanoparticles are removed by washing the monolith with strong base. Monolithic columns prepared using this procedure have exhibited a 33-fold increase in ion-exchange capacity when compared to untemplated monoliths prepared and treated under similar conditions. The templating procedure does not alter the macroporous properties of the polymer monolith, confirmed through scanning electron microscopy and BET surface area analysis, but provides increased capacity predominantly through the re-orientation of more carboxylic acid groups. The resulting increase in ion-exchange capacity has proven to be useful for the preconcentration and separation of neurotransmitters by in-line solid-phase extraction-capillary electrophoresis. The increased capacity of the templated monolith allowed the injection time to be increased 10 times over that of an untemplated monolith, allowing 10 times more s le to be injected with the efficiencies and recoveries remaining unaffected. The enhancement in sensitivity for the test mixture of neurotransmitter (dopamine, norepinephrine and metanephrine) ranged 1500-1900 compared to a normal hydrodynamic injection in capillary electrophoresis. Efficiencies obtained for the neurotransmitters were 100000-260000 plates, typical of those obtained in capillary zone electrophoresis. The applicability of the increased capacity silica nano-templated polymer monolith was demonstrated by analysing trace levels of caffeine in biological, food and environmental s les.

Stacking in a continuous sample flow interface in capillary electrophoresis

Publisher: Elsevier BV

Date: 08-2015

DOI: 10.1016/J.CHROMA.2015.06.040

Abstract: Using a tee connector in a commercial capillary electrophoresis instrument, the effect of field lified s le injection from both flowing and static s le volumes was investigated. It is shown that under identical conditions (40min electrokinetic injection at 5kV from a s le volume of 295μL) the limit of detection using the continuous s le flow interface is 4 times lower than from a static vial. The relationship between different flow rates and injection voltages on the injected s le amount was also investigated using a 2D axisymmetric simulation (COMSOL 4.3b) and verified experimentally, confirming conditions under which there is near-quantitative injection of the s le target ions. Using electrokinetic injection at 30kV and a flow rate of 558nL/s the same enhancement from an even smaller volume of 184μL could be achieved in 5.5min than could be achieved from 295μL and a 40min injection. This sensitivity enhancement factor corresponded to four orders of magnitude improvement compared to a hydrodynamic injection. This is the first report showing that a continuous s le flow interface combined with stacking methods under conditions approaching quantitative injection from the entire s le volume has the potential to be more sensitive than a static system.

Polymeric Microchip for the Simultaneous Determination of Anions and Cations by Hydrodynamic Injection Using a Dual-Channel Sequential Injection Microchip Electrophoresis System

Publisher: American Chemical Society (ACS)

Date: 17-03-2014

DOI: 10.1021/AC403627G

Abstract: A dual-channel sequential injection microchip capillary electrophoresis system with pressure-driven injection is demonstrated for simultaneous separations of anions and cations from a single s le. The poly(methyl methacrylate) (PMMA) microchips feature integral in-plane contactless conductivity detection electrodes. A novel, hydrodynamic "split-injection" method utilizes background electrolyte (BGE) sheathing to gate the s le flows, while control over the injection volume is achieved by balancing hydrodynamic resistances using external hydrodynamic resistors. Injection is realized by a unique flow-through interface, allowing for automated, continuous s ling for sequential injection analysis by microchip electrophoresis. The developed system was very robust, with in idual microchips used for up to 2000 analyses with lifetimes limited by irreversible blockages of the microchannels. The unique dual-channel geometry was demonstrated by the simultaneous separation of three cations and three anions in in idual microchannels in under 40 s with limits of detection (LODs) ranging from 1.5 to 24 μM. From a series of 100 sequential injections the %RSDs were determined for every fifth run, resulting in %RSDs for migration times that ranged from 0.3 to 0.7 (n = 20) and 2.3 to 4.5 for peak area (n = 20). This system offers low LODs and a high degree of reproducibility and robustness while the hydrodynamic injection eliminates electrokinetic bias during injection, making it attractive for a wide range of rapid, sensitive, and quantitative online analytical applications.

An Open Microfluidic Chip for Continuous Sampling of Solute from a Turbulent Particle Suspension

Publisher: Wiley

Date: 27-11-2021

DOI: 10.1002/ANGE.202012410

Scalable 3D printing method for the manufacture of single-material fluidic devices with integrated filter for point of collection colourimetric analysis

Publisher: Elsevier BV

Date: 03-2021

DOI: 10.1016/J.ACA.2020.11.033

Electric field gradient focusing using a variable width polyaniline electrode

Publisher: Wiley

Date: 02-10-2012

DOI: 10.1002/ELPS.201200335

Abstract: A new approach for electric field gradient focusing (EFGF) based on the use of a variable-width polyaniline (PANI) electrode is demonstrated. The electrode was created by patterning a PANI nanofibre film using a 635-nm laser and a computer-controlled XY stage. The electrode consisted of 16 segments of varying width, ranging from 200 to 5000 μm in 320 μm increments, with the resistance changing approximately 20-fold from 3881 to 198 kΩ at each extreme, respectively. Application of a voltage across the electrode established a voltage gradient resulting in a non-linear distribution of electrophoretic velocities along the microchannel. When balanced with a combination of hydrodynamic flow and EOF, the variable-width PANI electrode could be used for the concentration and separation of two cationic dyes, rhodamine 6G and quinine, which were concentrated by at least threefold within 10 min.

Correction to: Precise, accurate and user-independent blood collection system for dried blood spot sample preparation (Analytical and Bioanalytical Chemistry, (2018), 410, 14, (3315-3323), 10.1007/s00216-018-0993-y)

Publisher: Springer Science and Business Media LLC

Date: 30-04-2018

DOI: 10.1007/S00216-018-1100-0

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.

Optimisation of the separation of anions by ion chromatography–capillary electrophoresis using indirect UV detection

Publisher: Elsevier BV

Date: 06-2001

DOI: 10.1016/S0021-9673(00)01263-2

Abstract: The separation of a complex mixture of inorganic and organic anions by ion chromatography-capillary electrophoresis using a cationic polymer added to the background electrolyte and indirect UV detection has been studied. The addition of unmodified polymer to an electrolyte suitable for indirect detection resulted in the appearance of a system peak due to the counter-anion on the polymer and while the position of the analytes relative to this system peak could be changed, this was found to be an unacceptable approach for mixtures of large numbers of analytes. Although conversion of the polymer to replace the counter-ion with the indirect UV detection probe ion simplified the system, this approach restricted the flexibility of the system because the probe and polymer concentration were necessarily linked. This limitation could be overcome by selecting the appropriate type of probe ion, with probes having a low ion-exchange selectivity coefficient providing greater retention of analytes than probes with a high ion-exchange selectivity coefficient. Three electrolyte systems with different probes (benzoate, chromate and phthalate) were modelled using a previously derived migration equation and this was used to optimise the electrolyte composition to enable the separation of a mixture of 24 inorganic and organic anions within 7 min. The electrolyte composition was then optimised for the analysis of anions in Bayer liquor with the final separation selectivity being substantially improved for selected key analytes.

Salinity effects on chloroplast PSII performance in glycophytes and halophytes¹

Publisher: CSIRO Publishing

Date: 2016

DOI: 10.1071/FP16135

Abstract: The effects of NaCl stress and K+ nutrition on photosynthetic parameters of isolated chloroplasts were investigated using PAM fluorescence. Intact mesophyll cells were able to maintain optimal photosynthetic performance when exposed to salinity for more than 24 h whereas isolated chloroplasts showed declines in both the relative electron transport rate (rETR) and the maximal photochemical efficiency of PSII (Fv/Fm) within the first hour of treatment. The rETR was much more sensitive to salt stress compared with Fv/Fm, with 40% inhibition of rETR observed at apoplastic NaCl concentration as low as 20 mM. In isolated chloroplasts, absolute K+ concentrations were more essential for the maintenance of the optimal photochemical performance (Fv/Fm values) rather than sodium concentrations per se. Chloroplasts from halophyte species of quinoa (Chenopodium quinoa Willd.) and pigface (Carpobrotus rosii (Haw.) Schwantes) showed less than 18% decline in Fv/Fm under salinity, whereas the Fv/Fm decline in chloroplasts from glycophyte pea (Pisum sativum L.) and bean (Vicia faba L.) species was much stronger (31 and 47% respectively). Vanadate (a P-type ATPase inhibitor) significantly reduced Fv/Fm in both control and salinity treated chloroplasts (by 7 and 25% respectively), whereas no significant effects of gadolinium (blocker of non-selective cation channels) were observed in salt-treated chloroplasts. Tetraethyl ammonium (TEA) (K+ channel inhibitor) and amiloride (inhibitor of the Na+/H+ antiporter) increased the Fv/Fm of salinity treated chloroplasts by 16 and 17% respectively. These results suggest that chloroplasts’ ability to regulate ion transport across the envelope and thylakoid membranes play a critical role in leaf photosynthetic performance under salinity.

Microchip-Based Purification of DNA from Biological Samples

Publisher: American Chemical Society (ACS)

Date: 18-03-2003

DOI: 10.1021/AC0204855

Abstract: A microchip solid-phase extraction method for purification of DNA from biological s les, such as blood, is demonstrated. Silica beads were packed into glass microchips and the beads immobilized with sol-gel to provide a stable and reproducible solid phase onto which DNA could be adsorbed. Optimization of the DNA loading conditions established a higher DNA recovery at pH 6.1 than 7.6. This lower pH also allowed for the flow rate to be increased, resulting in a decrease in extraction time from 25 min to less than 15 min. Using this procedure, template genomic DNA from human whole blood was purified on the microchip platform with the only s le preparation being mixing of the blood with load buffer prior to loading on the microchip device. Comparison between the microchip SPE (microchipSPE) procedure and a commercial microcentrifuge method showed comparable amounts of PCR- lifiable DNA could be isolated from cultures of Salmonella typhimurium. The greatest potential of the microchipSPE device was illustrated by purifying DNA from spores from the vaccine strain of Bacillus anthracis, where eventual integration of SPE, PCR, and separation on a single microdevice could potentially enable complete detection of the infectious agent in less than 30 min.

Rapid Additive Manufacturing of 3D Geometric Structures via Dual-Wavelength Polymerization

Publisher: American Chemical Society (ACS)

Date: 08-09-2020

DOI: 10.1021/ACSMACROLETT.0C00465

In‐plane alloy electrodes for capacitively coupled contactless conductivity detection in poly(methylmethacrylate) electrophoretic chips

Publisher: Wiley

Date: 10-2013

DOI: 10.1002/ELPS.201300256

Abstract: A simple method for producing PMMA electrophoresis microchips with in-plane electrodes for capacitively coupled contactless conductivity detection is presented. One PMMA plate (channel plate) is embossed with the microfluidic and electrode channels and lamination bonded to a blank PMMA cover plate of equal dimensions. To incorporate the electrodes, the bonded chip is heated to 80 °C, above the melting point of the alloy (≈ 70 °C) and below the glass transition temperature of the PMMA (≈ 105 °C), and the molten alloy drawn into the electrode channels with a syringe before being allowed to cool and harden. A 0.5 mm diameter stainless steel pin is then inserted into the alloy filled reservoirs of the electrode channels to provide external connection to the capacitively coupled contactless conductivity detection detector electronics. This advance provides for a quick and simple manufacturing process and negates the need for integrating electrodes using costly and time-consuming thin film deposition methods. No additional detector cell mounting structures were required and connection to the external signal processing electronics was achieved by simply slipping commercially available shielded adaptors over the pins. With a non-optimised electrode arrangement consisting of a 1 mm detector gap and 100 μm insulating distance, rapid separations of ammonium, sodium and lithium (<22 s) yielded LODs of approximately 1.5-3.5 ppm.

Approaches to Enhancing the Sensitivity of Carbohydrate Separations in Capillary Electrophoresis

Publisher: Humana Press

Date: 2013

DOI: 10.1007/978-1-62703-296-4_3

Abstract: Electrophoresis in both capillaries (CE) and microchips (ME) is an extremely powerful liquid phase-separation technique that is indispensable for the separation of carbohydrates. It is capable of separating both small mono- and disaccharides, through to more complex oligo- and polysaccharides, with high resolution, but as with all CE and ME separations, the detection limits are often inferior to those that can be achieved with liquid chromatographic methods. One avenue to address this is to use an on-line concentration strategy. Various approaches have been developed over the past 20 years, and this chapter will highlight their application to improve the sensitivity of carbohydrate separations in both CE and ME.

Modelling of migration behaviour of inorganic anions in ion-exchange capillary electrochromatography

Publisher: Wiley

Date: 02-2001

DOI: 10.1002/1522-2683(200102)22:3<503::AID-ELPS503>3.0.CO;2-S

Cost-effective three-dimensional printing of visibly transparent microchips within minutes

Publisher: American Chemical Society (ACS)

Date: 24-02-2014

DOI: 10.1021/AC4041857

Abstract: One-step fabrication of transparent three-dimensional (3D) microfluidic to millifluidic devices was demonstrated using a commercial 3D printer costing $2300 with 500 mL of clear resin for $138. It employs dynamic mask projection stereolithography, allowing fast concept-to-chip time. The fully automated system allows fabrication of models of up to 43 mm × 27 mm × 180 mm (x × y × z) at printing speeds of 20 mm/h in height regardless of the design complexity. The minimal cross sectional area of 250 μm was achieved for monolithic microchannels and 200 μm for positive structures (templates for soft lithography). The colorless resin's good light transmittance (>60% transmission at wavelengths of >430 nm) allows for on-chip optical detection, while the electrically insulating material allows electrophoretic separations. To demonstrate its applicability in microfluidics, the printer was used for the fabrication of a micromixer, a gradient generator, a droplet extractor, and a device for isotachophoresis. The mixing and gradient formation units were incorporated into a device for analysis of nitrate in tap water with standard addition as a single run and multiple depth detection cells to provide an extended linear range.

Exploring colorimetric detection of perfluorooctane sulfonate using micelle solubilised porphyrin

Publisher: CSIRO Publishing

Date: 2023

DOI: 10.1071/CH23061

Electrokinetic and hydrodynamic injection: making the right choice for capillary electrophoresis

Publisher: Future Science Ltd

Date: 08-2009

DOI: 10.4155/BIO.09.73

Abstract: Dr Michael Breadmore is an Australian Research Council Queen Elizabeth II fellow with interests in the development of miniaturised analytical systems for the improved ana lysis of drugs and metabolites in biological fluids. He is based at the Australian Center for Research on Separation Science (ACROSS) at the University of Tasmania, Australia. He has spent the last 10 years developing novel electrophoresis methods for a range of applications with a particular interest in new ways to enhance the sensitivity. CE is a powerful liquid-phase separation technique that is an attractive alternative to HPLC because of its small s le requirements, high resolving power and excellent mass detection limits. While there are many similarities between the two techniques, there are also many differences, some obvious, some subtle. One of the often overlooked differences is the way s le is injected. In HPLC, injection is a very minor component of the method and the choice is predominantly restricted to the choice of solvent and the injection volume. But in CE, it is vastly more complex, and development of an appropriate injection strategy should be given consideration during any method development. While the choice between hydrodynamic or electrokinetic injection may not initially be given any thought, selection of the right approach for the right application can lead to significant improvements in performance, particularly with regard to achieving the lowest detection limits possible. The question is how to decide the best way to inject for each application?

Electrokinetic Extraction of Doxorubicin from Biological Fluids by Polymer Inclusion Membrane Sampling Probe

Publisher: American Chemical Society (ACS)

Date: 17-01-2023

DOI: 10.1021/ACS.ANALCHEM.2C02937

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2008–2010)

Publisher: Wiley

Date: 29-04-2020

DOI: 10.1002/ELPS.201000412

Abstract: Capillary electrophoresis has been alive for over two decades now yet, its sensitivity is still regarded as being inferior to that of more traditional methods of separation such as HPLC. As such, it is unsurprising that overcoming this issue still generates much scientific interest. This review continues to update this series of reviews, first published in Electrophoresis in 2007, with an update published in 2009 and covers material published through to June 2010. It includes developments in the fields of stacking, covering all methods from field- lified s le stacking and large volume s le stacking, through to ITP, dynamic pH junction and sweeping. Attention is also given to on-line or in-line extraction methods that have been used for electrophoresis.

Capillary electrophoresis of neurotransmitters using in-line solid-phase extraction and preconcentration using a methacrylate-based weak cation-exchange monolithic stationary phase and a pH step gradi

Publisher: Elsevier BV

Date: 12-2007

DOI: 10.1016/J.CHROMA.2007.09.069

Abstract: A novel approach for in-line solid-phase extraction capillary electrophoresis (SPE-CE) for basic analytes was developed. The method is based on the use of a weak cation-exchange monolith synthesised in situ in the front end of the CE capillary via photoinitiated polymerization to form poly(methacrylic acid-co-ethylene glycol dimethacrylate), which was used to create the SPE phase in-line with the CE separation capillary. The monolithic SPE material exhibited a surface area of 23.1 m2/g and a capacity of 403 nM for dopamine. Adsorption of the analytes as protonated, cationic species onto the SPE phase was achieved using an electrolyte of 6 mM phosphate and 12 mM sodium ion, buffered at pH 7.0, which is above the pKa of the monolith but below the pKa of the analytes. Elution of the analytes from the SPE phase was achieved using an electrolyte with a pH below that of the pKa of the monolith, namely 12 mM phosphate and 12 mM sodium ion, buffered at pH 3.0. Due to the discontinuous electrolyte combination, analytes were simultaneously eluted and focused as the electrophoretically mobilised pH step boundary moved through the SPE monolith, after which the analytes were separated by conventional CZE in the remainder of the capillary. Quantitative extraction from a solution of 0.5 microg/ml dopamine and epinephrine was achieved when flushing up to 15 column volumes of s le through the capillary. The limits of detection (S/N=3) for dopamine and epinephrine were 3.7 and 4.3 ng/ml, and this method provided a sensitivity enhancement for dopamine of 462 times compared to CZE using hydrodynamic injection. The developed method was used to preconcentrate a test mixture of neurotransmitters comprising dopamine, epinephrine, 5-hydroxytryptamine, metanephrine and also histamine. The applicability of this approach to real life s les was demonstrated by using a urine s le from a healthy person to detect dopamine at sub-ppm levels.

Dynamic high‐resolution computer simulation of electrophoretic enantiomer separations with neutral cyclodextrins as chiral selectors

Publisher: Wiley

Date: 03-2012

DOI: 10.1002/ELPS.201100472

Abstract: GENTRANS, a comprehensive one-dimensional dynamic simulator for electrophoretic separations and transport, was extended for handling electrokinetic chiral separations with a neutral ligand. The code can be employed to study the 1:1 interaction of monovalent weak and strong acids and bases with a single monovalent weak or strong acid or base additive, including a neutral cyclodextrin, under real experimental conditions. It is a tool to investigate the dynamics of chiral separations and to provide insight into the buffer systems used in chiral capillary zone electrophoresis (CZE) and chiral isotachophoresis. Analyte stacking across conductivity and buffer additive gradients, changes of additive concentration, buffer component concentration, pH, and conductivity across migrating s le zones and peaks, and the formation and migration of system peaks can thereby be investigated in a hitherto inaccessible way. For model systems with charged weak bases and neutral modified β-cyclodextrins at acidic pH, for which complexation constants, ionic mobilities, and mobilities of selector-analyte complexes have been determined by CZE, simulated and experimentally determined electropherograms and isotachopherograms are shown to be in good agreement. Simulation data reveal that CZE separations of cationic enantiomers performed in phosphate buffers at low pH occur behind a fast cationic migrating system peak that has a small impact on the buffer composition under which enantiomeric separation takes place.

Capillary electrophoretic separation of mono- and di-saccharides with dynamic pH junction and implementation in microchips

Publisher: Royal Society of Chemistry (RSC)

Date: 2010

DOI: 10.1039/C0AN00010H

Abstract: An electrophoretic method for the separation of derivatised mono- and di-saccharides with on-line concentration via dynamic pH junction has been developed and optimised in capillaries. Dynamic pH junction is perfectly suited for on-line concentration of derivatised sugars due to the acidic derivatisation conditions, however, most reagents for carbohydrates are not ionisable, requiring the use of the novel reagent, O-2-[aminoethyl]fluorescein. Optimisation of the separation selectivity yielded best separations with 170 mM ammonium borate buffer at pH 8.60 in an acrylamide coated capillary. When using an injection comprising 7% of the capillary volume and detection via laser induced fluorescence (LIF) with an argon ion laser, limits of detection as low as 0.13 nM for maltose were obtained, which was 10 times lower than could be achieved without on-line concentration. In order to implement this system in a glass/PDMS microchip, the low pH s le was introduced into the microchannels via a cathodic pH independent electro-osmotic flow (EOF) generated using a poly(dimethyldiallylmethyl-ammonium chloride) (PDADMAC) oly(styrene sulfonate) (PSS) polyelectrolyte multilayer coating. Optimisation of the injection volume in capillaries greatly simplified translation to the microchip platform, with the optimum capillary s le volume of 7%, dictating the use of an off-set cross with a volume 7% of the separation channel. Microchip separations of maltose, glucose, galactose and allose with dynamic pH junction, were achieved within 120 s, with the limit of detection of maltose using a light emitting diode induced fluorescence (LEDIF) detection system being 790 nM. This is 10 times lower than that achieved without concentration, and is lower than other reports of derivatised sugars using LEDIF detection. This is the first implementation of on-line concentration via a dynamic pH junction in a microchip, and significantly, the improvement in sensitivity achieved when translated to the microchip was equivalent to that achieved in capillaries.

Porous layer open tubular monolith capillary column: switching-off the reaction kinetics as the governing factor in their preparation by using an immiscible liquid-controlled polymerization

Publisher: Royal Society of Chemistry (RSC)

Date: 2013

DOI: 10.1039/C2RA23417C

Sensitive determination of carbohydrates labelled with p-nitroaniline by capillary electrophoresis with photometric detection using a 406 nm light-emitting diode

Publisher: Wiley

Date: 10-2006

DOI: 10.1002/ELPS.200500856

Abstract: p-Nitroaniline was explored as a derivatising reagent for UV absorbance detection of carbohydrates after separation by CE. This derivatising agent has three advantages: first, it has excellent water solubility second, it has high molar absorptivity and third, it is possible to obtain sensitive detection using a UV or blue light-emitting diode (LED) as the light source. The labelling reaction took less than 30 min to complete with high reaction yield. The separation process was modelled and optimised using an artificial neural network. Nine carbohydrates were separated by a CE system within 16 min using a 0.17 M boric acid buffer at pH 9.7. On-column LED detection at 406 nm allowed the detection of carbohydrates with good detection limits (<1.1 microM or 8.8 fmol) and reproducible quantification in the concentration range of 2.6-200 microM. This method was applied successfully to the determination of component carbohydrates in some food s les.

Chemical vapour deposition in narrow capillaries: Electro-osmotic flow control in capillary electrophoresis

Publisher: Elsevier BV

Date: 11-2023

DOI: 10.1016/J.ACA.2023.341847

An Open Microfluidic Chip for Continuous Sampling of Solute from a Turbulent Particle Suspension

Publisher: Wiley

Date: 27-11-2021

DOI: 10.1002/ANIE.202012410

A simple PDMS-based electro-fluidic interface for microchip electrophoretic separations

Publisher: Royal Society of Chemistry (RSC)

Date: 25-11-2002

DOI: 10.1039/B206808G

Abstract: High voltage electrodes for electrophoresis have been integrated into a polymer layer that can be reversibly bound to glass microchips for electrophoretic separations. By using the liquid precursor to the polymer polydimethylsiloxane (PDMS), platinum electrodes and reservoirs can be positioned prior to solidification, providing a simple and flexible method for electrode interface construction. Field strengths up to 875 V cm(-1) over an 8 cm separation channel can be applied to the system without any loss in performance of the interface. The interface can function as an electro-fluidic interface between the high voltage power supply and the separation channel and, when reversibly sealed to an etched glass plate, functions as a cover plate establishing a hybrid PDMS-glass microchip in which the electrodes are directly integrated onto the device. The versatility of this approach is not only demonstrated by separating DNA fragments in a novel buffer sieving matrix, but also with the molecular diagnostic analysis of a variety of DNA s les for Duschenne Muscular Dystrophy and cytomegalovirus (CMV) infection, using both microchip interface configurations.

Hydroxypropyl Cellulose as an Adsorptive Coating Sieving Matrix for DNA Separations:  Artificial Neural Network Optimization for Microchip Analysis

Publisher: American Chemical Society (ACS)

Date: 17-01-2003

DOI: 10.1021/AC020425Z

Abstract: Effective DNA separations in microelectrophoretic systems are complicated by the need to passivate the surface dynamically or covalently. We describe the optimization and utilization of a novel buffer system for fast DNA separations by capillary and microchip electrophoresis without the need for any surface modification or conditioning prior to separation. At concentrations as high as 5%, hydroxypropyl cellulose (HPC) has a relatively low viscosity, allowing for microchip channel filling to be performed with ease. A MES/TRIS buffer system at pH 6.1 eliminates the need for surface preconditioning procedures due to the promotion of hydrogen bonding of HPC with the wall. An additional benefit with this buffer system is the low current observed at high fields when compared to other common DNA separation buffers. An artificial neural network (ANN) was used to model the data and to predict the optimum conditions. Utility of the ANN-optimized system for molecular diagnostic testing was demonstrated by performing microchip separations on DNA s les from patients suspected of having genetic mutations associated with Duchenne muscular dystrophy (DMD). Microchip analysis easily allowed for the patient s les positive for DMD mutations to be distinguished from patient s les negative for the disease.

Capillary electrophoresis ribosomal RNA single-stranded conformation polymorphism: a new approach for characterization of low-diversity microbial communities

Publisher: Springer Science and Business Media LLC

Date: 03-08-2012

DOI: 10.1007/S00216-012-6268-0

Abstract: Capillary electrophoresis (CE) has been the principle system for nucleic acid analysis since the early 1990s due to its inherent advantages such as fast analysis time, high resolution and efficiency, minimal s le requirement, high detection sensitivity, and automation. In the past few decades, microbial community fingerprinting methods such as terminal restriction fragment length polymorphism and single-stranded conformation polymorphism (SSCP) have migrated to CE to utilize its advantages over conventional slab gel electrophoresis. Recently, a gel-based direct rRNA fingerprint method was demonstrated. Different from other existing microbial community characterization approaches, this novel approach is polymerase chain reaction free and capable of providing information on the relative abundance of rRNA from in idual phylotypes in low- ersity s les. As a gel-based method, it has a long analysis time and relatively large reagent and s le requirements. Here, we addressed these limitations by transferring the RNA fingerprint approach to the CE platform. Analysis time significantly improved from 24 h to 60 min, and the use of a fluorescently labeled hybridization probe as the detection strategy decreased the s le requirement by ten-fold. The combination of fast analysis time, low s le requirement, and sensitive fluorescence detection makes CE-RNA-SSCP an appealing new approach for characterizing low- ersity microbial communities.

Potassium retention in leaf mesophyll as an element of salinity tissue tolerance in halophytes

Publisher: Elsevier BV

Date: 12-2016

DOI: 10.1016/J.PLAPHY.2016.10.011

Abstract: Soil salinity remains a major threat to global food security, and the progress in crop breeding for salinity stress tolerance may be achieved only by pyramiding key traits mediating plant adaptive responses to high amounts of dissolved salts in the rhizosphere. This task may be facilitated by studying natural variation in salinity tolerance among plant species and, specifically, exploring mechanisms of salinity tolerance in halophytes. The aim of this work was to establish the causal link between mesophyll ion transport activity and plant salt tolerance in a range of evolutionary contrasting halophyte and glycophyte species. Plants were grown under saline conditions in a glasshouse, followed by assessing their growth and photosynthetic performance. In a parallel set of experiments, net K

Identification of inorganic ions in post-blast explosive residues using portable CE instrumentation and capacitively coupled contactless conductivity detection

Publisher: Wiley

Date: 11-2008

DOI: 10.1002/ELPS.200800226

Abstract: Novel CE methods have been developed on portable instrumentation adapted to accommodate a capacitively coupled contactless conductivity detector for the separation and sensitive detection of inorganic anions and cations in post-blast explosive residues from homemade inorganic explosive devices. The methods presented combine sensitivity and speed of analysis for the wide range of inorganic ions used in this study. Separate methods were employed for the separation of anions and cations. The anion separation method utilised a low conductivity 70 mM Tris/70 mM CHES aqueous electrolyte (pH 8.6) with a 90 cm capillary coated with hexadimethrine bromide to reverse the EOF. Fifteen anions could be baseline separated in 7 min with detection limits in the range 27-240 microg/L. A selection of ten anions deemed most important in this application could be separated in 45 s on a shorter capillary (30.6 cm) using the same electrolyte. The cation separation method was performed on a 73 cm length of fused-silica capillary using an electrolyte system composed of 10 mM histidine and 50 mM acetic acid, at pH 4.2. The addition of the complexants, 1 mM hydroxyisobutyric acid and 0.7 mM 18-crown-6 ether, enhanced selectivity and allowed the separation of eleven inorganic cations in under 7 min with detection limits in the range 31-240 microg/L. The developed methods were successfully field tested on post-blast residues obtained from the controlled detonation of homemade explosive devices. Results were verified using ion chromatographic analyses of the same s les.

In-Syringe Electrokinetic Ampholytes Focusing Coupled with Electrospray Ionization Mass Spectrometry

Publisher: American Chemical Society (ACS)

Date: 29-05-2019

DOI: 10.1021/ACS.ANALCHEM.9B00942

Abstract: A 25 μL analytical glass syringe has been used for isoelectric focusing (IEF) utilizing the stainless-steel needle and plunger as electrodes. The generation of protons and hydroxyl ions at the electrodes facilitated a neutralization reaction boundary (NRB) mechanism to focus different hoteric compounds, such as hemoglobin, bovine serum albumin, R-phycoerythrin, and histidine, within minutes. After optimization of different experimental parameters affecting the IEF process and the coupling of the IEF syringe with electrospray ionization mass spectrometry (ESI-MS), a BGE composed of NH

Microfluidic chips for capillary electrophoresis with integrated electrodes for capacitively coupled conductivity detection based on printed circuit board technology

Publisher: Elsevier BV

Date: 11-2011

DOI: 10.1016/J.SNB.2011.06.023

Recent significant developments in detection and method development for the determination of inorganic ions by CE

Publisher: Wiley

Date: 06-2009

DOI: 10.1002/ELPS.200900103

Abstract: CE has been available as a tool for almost 20 years, but it is only in the past several years that it has been implemented widely. This has been the result of some significant advances in the technique. These fall in the areas of indirect photometric detection (through the use of dyes as probes and LEDs as light sources), the introduction and establishment of capacitively-coupled contactless conductivity detection (C4D) as a routine, sensitive and commercially available detection method, and in software capable of simulation of separations and the selection of optimal composition of the BGE. These developments are reviewed and their impact illustrated by reference to a case study involving the rapid separation and sensitive detection of 15 anions and 12 cations on a portable CE instrument. It is shown that C4D provides considerably superior detection sensitivity (by a factor of about 8 in comparison with optimised indirect photometry).

Microfluidic Device for Studying Traumatic Brain Injury

Publisher: Springer New York

Date: 2017

DOI: 10.1007/978-1-4939-7024-7_10

Using Printing Orientation for Tuning Fluidic Behavior in Microfluidic Chips Made by Fused Deposition Modeling 3D Printing

Publisher: American Chemical Society (ACS)

Date: 17-11-2017

DOI: 10.1021/ACS.ANALCHEM.7B03228

Abstract: Fluidic behavior in microfluidic devices is dictated by low Reynolds numbers, complicating mixing. Here, the effect of the orientation of the extruded filament on the fluidic behavior is investigated in fused deposition modeling (FDM) printed fluidic devices. Devices were printed with filament orientations at 0°, 30°, 60°, and 90° to the direction of the flow. The extent of mixing was observed when pumping yellow and blue solutions into the inlets of a Y-shaped device, and measuring the extent of mixing of two colored solutions under different angles and at flow rates of 25, 50, and 100 μL/min. Fluidic devices printed with filament extruded at 60° to the flow showed the highest mixing efficiency, but results obtained at 30° suggested more complex fluid movement, as the measured degree of mixing decreased along the fluidic channel at higher flow rates. To explore this, a device with -37° filament orientation on the top surface was designed to align with the direction of the first fluid input channel and +37° on the bottom surface of the channel to align with the direction of the second fluidic input. Results indicated a rotational movement of the fluids down the microchannel, which were confirmed by computational fluid dynamics. These results demonstrate the impact of the filament extrusion direction on fluidic behavior in microfluidic devices made by FDM printing. Two chips with laminar flow (0° filament direction) or mixing flow (+37/-37° filament direction) were used to perform isotachophoresis and colorimetric detection of iron in river water, respectively, demonstrating the simplicity with which the same device can be tuned for different applications simply by controlling the way the device is printed.

Cheers: cracking open the bottleneck of extraction in bioanalysis

Publisher: Future Science Ltd

Date: 12-2015

DOI: 10.4155/BIO.15.212

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.

Precise, accurate and user-independent blood collection system for dried blood spot sample preparation

Publisher: Springer Science and Business Media LLC

Date: 05-04-2018

DOI: 10.1007/S00216-018-0993-Y

Abstract: An accurate and precise 3 μL blood collection and dispensing system is presented for the preparation of dried blood spot (DBS) s les. Using end-to-end glass capillaries in conjugation with pre-punched DBS pads, a blood micro collection system was developed to eliminate the haematocrit dispersion, widely associated with DBS technology, while providing better levels of accuracy and precision during s le preparation. This methodology is compared to traditional micro-volume blood collection systems, such as a pipette and a digitally controlled analytical syringe. Results showed that % of recovery for the capillary methodology was closer to 100% across the three haematocrit (HCT) levels tested and when prepared by two users (98 to 100% for capillaries, 78 to 104% for pipette and 93 to 97% for digital syringe) attesting a higher accuracy. Additionally, by taking advantage of the capillary action mechanism to collect and dispense autonomously the desired volume of blood onto the DBS pad, coefficients of variation between two in iduals were significantly lower than with standard methodologies (capillaries-0.05 to 0.77%, pipette-12.71 to 18.53% and digital syringe-0.72 to 1.77%). This alternate aspiration and dispensing methodology could be used by different users without compromising accuracy or precision when handling low volumes of blood during the pre-analytical steps. Graphical abstract Comparison of novel capillary dispensing methodology for dried blood spot s le preparation with pipette and digital syringe methodologies through accuracy and precision measurements of caffeine.

Editors’ Tribute to Professor Hanfa Zou

Publisher: Elsevier BV

Date: 02-2017

DOI: 10.1016/J.CHROMA.2017.01.028

Increasing the functionalities of 3D printed microchemical devices by single material, multimaterial, and print-pause-print 3D printing

Publisher: Royal Society of Chemistry (RSC)

Date: 2019

DOI: 10.1039/C8LC00826D

Abstract: 3D printing has emerged as a valuable approach for the fabrication of fluidic devices and may replace soft-lithography as the method of choice for rapid prototyping.

Capillary electrophoresis for the analysis of paralytic shellfish poisoning toxins in shellfish: Comparison of detection methods

Publisher: Wiley

Date: 13-04-2014

DOI: 10.1002/ELPS.201300353

Abstract: Paralytic shellfish toxins (PSTs) are produced by marine and freshwater microalgae and accumulate in shellfish including mussels, oysters, and scallops, causing possible fatalities when inadvertently consumed. Monitoring of PST content of shellfish is therefore important for food safety, with currently approved methods based on HPLC, using pre- or postcolumn oxidation for fluorescence detection (HPLC-FLD). CE is an attractive alternative for screening and detection of PSTs as it is compatible with miniaturization and could be implemented in portable instrumentation for on-site monitoring. In this study, CE methods were developed for C(4) D, FLD, UV absorption detection, and MS-making this first report of C(4) D and FLD for PSTs detection. Because most oxidized toxins are neutral, MEKC was used in combination with FLD. The developed CZE-UV and CZE-C(4) D methods provide better resolution, selectivity, and separation efficiency compared to CZE-MS and MEKC-FLD. The sensitivity of the CZE-C(4) D and MEKC-FLD methods was superior to UV and MS, with LOD values ranging from 140 to 715 ng/mL for CZE-C(4) D and 60.9 to 104 ng/mL for MEKC-FLD. With the regulatory limit for shellfish s les of 800 ng/mL, the CZE-C(4) D and MEKC-FLD methods were evaluated for the screening and detection of PSTs in shellfish s les. While the CZE-C(4) D method suffered from significant interferences from the shellfish matrix, MEKC-FLD was successfully used for PST screening of a periodate-oxidized mussel s le, with results confirmed by HPLC-FLD. This confirms the potential of MEKC-FLD for screening of PSTs in shellfish s les.

Separation of carboxylic acids in human serum by isotachophoresis using a commercial field-deployable analytical platform combined with in-house glass microfluidic chips

Publisher: Elsevier BV

Date: 11-2012

DOI: 10.1016/J.ACA.2012.10.022

Abstract: Portable and field deployable analytical instruments are attractive in many fields including medical diagnostics, where point of care and on-site diagnostics systems capable of providing rapid quantitative results have the potential to vastly improve the productivity and the quality of medical care. Isotachophoresis (ITP) is a well known electrophoretic separation technique previously demonstrated as suitable for miniaturization in microfluidic chip format (chip-ITP). In this work, a purpose-designed ITP chip compatible with a commercial end-used targeted microfluidic system was used to study different injection protocols and to evaluate the effect of the length of the separation channel on the analytical performance. The in-house ITP chips were made from Corning glass and compared to the commercial DNA chip for the ITP separation of anions from the hydrodynamic injection of human serum. Using the in-house ITP chip the isotachophoretic step of lactate from human serum was approximately two times longer. The results of this research suggested that microfluidic ITP with indirect fluorescence detection is a viable technique for separation of organic acids in human serum s les, especially when a chip with suitable design is used.

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2016–2018)

Publisher: Wiley

Date: 06-11-2018

DOI: 10.1002/ELPS.201800384

Abstract: One of the most cited limitations of capillary and microchip electrophoresis is the poor sensitivity. This review continues to update this series of biannual reviews, first published in Electrophoresis in 2007, on developments in the field of online/in-line concentration methods in capillaries and microchips, covering the period July 2016-June 2018. It includes developments in the field of stacking, covering all methods from field- lified s le stacking and large-volume s le stacking, through to isotachophoresis, dynamic pH junction, and sweeping. Attention is also given to online or in-line extraction methods that have been used for electrophoresis.

Lab-on-a-Chip device with laser-patterned polymer electrodes for high voltage application and contactless conductivity detection

Publisher: Royal Society of Chemistry (RSC)

Date: 2012

DOI: 10.1039/C2CC33693F

Abstract: A laser-patterned microchip electrophoresis device with integrated polymer electrodes for DC high voltages and AC capacitively-coupled contactless conductivity detection was developed. Electrophoresis separations comparable to devices with metal electrodes were obtained, at approximately 20 times lower cost.

Identification of inorganic improvised explosive devices by analysis of postblast residues using portable capillary electrophoresis instrumentation and indirect photometric detection with a light-emitting diode

Publisher: American Chemical Society (ACS)

Date: 18-08-2007

DOI: 10.1021/AC0708792

Abstract: A commercial portable capillary electrophoresis (CE) instrument has been used to separate inorganic anions and cations found in postblast residues from improvised explosive devices (IEDs) of the type used frequently in terrorism attacks. The purpose of this analysis was to identify the type of explosive used. The CE instrument was modified for use with an in-house miniaturized light-emitting diode (LED) detector to enable sensitive indirect photometric detection to be employed for the detection of 15 anions (acetate, benzoate, carbonate, chlorate, chloride, chlorite, cyanate, fluoride, nitrate, nitrite, perchlorate, phosphate, sulfate, thiocyanate, thiosulfate) and 12 cations (ammonium, monomethylammonium, ethylammonium, potassium, sodium, barium, strontium, magnesium, manganese, calcium, zinc, lead) as the target analytes. These ions are known to be present in postblast residues from inorganic IEDs constructed from ammonium nitrate/fuel oil mixtures, black powder, and chlorate erchlorate/sugar mixtures. For the analysis of cations, a blue LED (470 nm) was used in conjunction with the highly absorbing cationic dye, chrysoidine (absorption maximum at 453 nm). A nonaqueous background electrolyte comprising 10 mM chrysoidine in methanol was found to give greatly improved baseline stability in comparison to aqueous electrolytes due to the increased solubility of chrysoidine and its decreased adsorption onto the capillary wall. Glacial acetic acid (0.7% v/v) was added to ensure chrysoidine was protonated and to enhance separation selectivity by means of complexation with transition metal ions. The 12 target cations were separated in less than 9.5 min with detection limits of 0.11-2.30 mg/L (calculated at a signal-to-noise ratio of 3). The anions separation system utilized a UV LED (370 nm) in conjunction with an aqueous chromate electrolyte (absorption maximum at 371 nm) consisting of 10 mM chromium(VI) oxide and 10 mM sodium chromate, buffered with 40 mM tris(hydroxymethyl)aminomethane at pH 8.05. All 15 target anions were baseline separated in less than 9 min with limits of detection ranging from 0.24 to 1.15 mg/L (calculated at a signal-to-noise ratio of 3). Use of the portable instrumentation in the field was demonstrated by analyzing postblast residues in a mobile laboratory immediately after detonation of the explosive devices. Profiling the ionic composition of the inorganic IEDs allowed identification of the chemicals used in their construction.

Peak shapes in open tubular ion-exchange capillary electrochromatography of inorganic anions

Publisher: Elsevier BV

Date: 09-2000

DOI: 10.1016/S0021-9673(00)00092-3

Abstract: An experimental study of parameters influencing peak shapes in ion-exchange open tubular (OT) capillary electrochromatography (CEC) was conducted using adsorbed quaternary aminated latex particles as the stationary phase. The combination of separation mechanisms from both capillary electrophoresis and ion-exchange chromatography results in peak broadening in OT-CEC arising from both these techniques. The sources of peak broadening that were considered included the relative electrophoretic mobilities of the eluent co-ion and analyte, and resistance to mass transfer in both the mobile and stationary phases. The parameters investigated were the mobility of the eluent co-ion, column diameter, separation temperature and secondary interactions between the analyte and the stationary phase. The electromigration dispersion was found to influence peak shapes to a minor extent, indicating that chromatographic retention was the dominant source of dispersion. Improving the resistance to mass transfer in the mobile phase by decreasing the capillary diameter improved peak shapes, with symmetrical peaks being obtained in a 25 microm I.D. column. However, an increase in temperature from 25 degrees C to 55 degrees C failed to show any significant improvement. The addition of p-cyanophenol to the mobile phase to suppress secondary interactions with the stationary phase did not result in the expected improvement in efficiency.

Indirect photometric detection of anions in nonaqueous capillary electrophoresis employing orange G as probe and a light-emitting diode-based detector

Publisher: Wiley

Date: 07-2008

DOI: 10.1002/ELPS.200800116

Abstract: A method based on indirect photometric detection (IPD) in CE employing a blue LED (473 nm) as a light source and the highly absorbing (478 nm) anionic dye, Orange G, as the probe ion was developed for the sensitive analysis of inorganic and organic anions. The use of nonaqueous solvents was examined as a simple way to reduce the adsorption of the dye onto the capillary wall and to thereby improve the baseline stability. The benefits of this approach were confirmed by experiments using BGEs in methanol (MeOH) and DMSO in which superior baselines were obtained relative to those achieved using aqueous electrolyte systems. A range of commercial LEDs was tested to improve the detection performance, with a difference of 25% in sensitivity being observed between the best and worst performing LED. The final system (4 mM Orange G, 0.05% w/v hydroxypropylcellulose (HPC), 20 mM triethanolamine (TEA) in pure MeOH) exhibited stable baselines and very low LODs (0.10-0.18 microM) for a test mixture comprising nine inorganic and organic anions. These values represent a two- to six-fold improvement over previous studies and the proposed method provides the most sensitive IPD method for the determination of anions using CE published to date. RSDs for ten replicates were in the ranges of 0.42-0.62% for migration time, 1.41-3.46% for peak area and 3.20-5.78% for peak height.

Multi‐wavelength light emitting diode array as an excitation source for light emitting diode‐induced fluorescence detection in capillary electrophoresis

Publisher: Wiley

Date: 23-07-2010

DOI: 10.1002/ELPS.201000071

Abstract: A multi-wavelength LED array was used as an excitation source for in-column fiber-optic LED-induced fluorescence for CE. The light source consisted of a multi-wavelength LED array consisting of three different LEDs (430, 450 and 480 nm), a focusing lens and a gradient index lens group. The LED beam was collimated and reshaped with the gradient index lens group for coupling the LED light source into a single-mode optical fiber. In addition, the luminance and stability of the LED light source was improved by powering the LED under constant current at enhanced voltages. The benefits of this system were demonstrated by the simultaneous determination of FITC-labeled L-asparagine (Ex/Em 488/520 nm), 4-fluoro-7-nitro-2,1,3-benzoxadiazole-labeled epinephrine (Ex/Em 468/530 nm) and 3-(4-carboxybenzoyl)-quinoline-2-carboxaldehyde-labeled L-leucine (Ex/Em 440/530 nm). Detection limits of L-asparagine, epinephrine and L-leucine were estimated to be 0.8 x 10(-9), 12.0 x 10(-8) and 4.0 x 10(-8) M (S/N=3), respectively. The RSDs (n=6) for migration time and peak area were better than 0.71 and 0.92%, respectively. The performance of the developed multi-wavelength LED excitation source was compared to the use of a single-wavelength LED and found to provide superior sensitivity for the three fluorophores used in this study.

Good Practices and Practical Considerations for Research with Perfluoroalkyl Substances

Publisher: Wiley

Date: 27-09-2023

DOI: 10.1002/CMTD.202300017

Mild and repetitive very mild axonal stretch injury triggers cystoskeletal mislocalization and growth cone collapse

Publisher: Public Library of Science (PLoS)

Date: 04-05-2017

DOI: 10.1371/JOURNAL.PONE.0176997

Fluorophores and chromophores for the separation of carbohydrates by capillary electrophoresis

Publisher: Humana Press

Date: 04-10-2011

DOI: 10.1007/978-1-60761-875-1_2

Capillary and microchip electrophoresis: Challenging the common conceptions

Publisher: Elsevier BV

Date: 2012

DOI: 10.1016/J.CHROMA.2011.09.062

Abstract: Capillary electrophoresis (CE) has long been regarded as a powerful analytical separation technique that is an alternative to more traditional methods such as gel electrophoresis (GE) and liquid chromatography (LC). It is often touted as having a number of advantages over both of these, such as speed, flexibility, portability, s le and reagent requirements and cost, but also a number of disadvantages such as reproducibility and sensitivity. Microchip electrophoresis (ME), the next evolutionary step, miniaturised CE further providing improvements in speed and s le requirements as well as the possibility to perform more complex and highly integrated analyses. CE and ME are seen as a viable alternative to GE, but are often considered to be inferior to LC. This review will consider the strengths and weaknesses of both CE and ME and will challenge the common conceptions held about these.

Porphyrin-based colorimetric sensing of perfluorooctanoic acid as proof of concept for perfluoroalkyl substance detection

Publisher: Royal Society of Chemistry (RSC)

Date: 2021

DOI: 10.1039/D1CC04903H

Abstract: A color changing sensor for the pollutant perfluorooctanoic acid was developed. The pollutant was visually detected from soil at concentrations as low as 3 ppm.

Preconcentration and frontal electroelution of amino acids for in-line solid-phase extraction–capillary electrophoresis

Publisher: Elsevier BV

Date: 2006

DOI: 10.1016/J.ACA.2005.07.069

Abstract: A new frontal electroelution approach that can be used for the preconcentration of amino acids in in-line solid-phase extraction-capillary electrophoresis (SPE-CE) has been developed. A single capillary was employed featuring a short monolithic SPE column created inside the capillary via photo-initiated, free-radical polymerisation of 3-sulfopropyl methacrylate and butyl methacrylate monomers. A weak electrolyte of dilute H2SO4, pH 2.9, was found to promote adsorption of the amino acids onto the SPE column. Elution of the amino acids was achieved using a dual solvation/ion-exchange transient boundary mobilised via EOF by using a strong electrolyte containing 62.5mM ethylenediamine, pH 2.9 with H2SO4 and 40% (v/v) acetonitrile. Using these two electrolytes, tryptophan was adsorbed onto the SPE column in weak electrolyte and eluted via a frontal electroelution mechanism in the strong electrolyte. Injections up to 20 min, corresponding to over 14 column volumes (or 1400% of the capillary volume) of s le provided quantitative extraction of tryptophan from the weak electrolyte and were eluted without any loss in efficiency. This represents a practical increase of approximately 300-fold when compared to a typical hydrodynamic injection occupying 5% of the capillary volume.

High‐resolution electrophoretic simulations: Performance characteristics of one‐dimensional simulators

Publisher: Wiley

Date: 02-2011

DOI: 10.1002/ELPS.201000517

Abstract: Three comprehensive one-dimensional simulators were used on the same PC to simulate the dynamics of different electrophoretic configurations, including two migrating hybrid boundaries, an isotachophoretic boundary and the zone electrophoretic separation of ten monovalent anions. Two simulators, SIMUL5 and GENTRANS, use a uniform grid, while SPRESSO uses a dynamic adaptive grid. The simulators differ in the way components are handled. SIMUL5 and SPRESSO feature one equation for all components, whereas GENTRANS is based on the use of separate modules for the different types of monovalent components, a module for multivalent components and a module for proteins. The code for multivalent components is executed more slowly compared to those for monovalent components. Furthermore, with SIMUL5, the computational time interval becomes smaller when it is operated with a reduced calculation space that features moving borders, whereas GENTRANS offers the possibility of using data smoothing (removal of negative concentrations), which can avoid numerical oscillations and speed up a simulation. SPRESSO with its adaptive grid could be employed to simulate the same configurations with smaller numbers of grid points and thus is faster in certain but not all cases. The data reveal that simulations featuring a large number of monovalent components distributed such that a high mesh is required throughout a large proportion of the column are fastest executed with GENTRANS.

100 000-Fold Concentration of Anions in Capillary Zone Electrophoresis Using Electroosmotic Flow Controlled Counterflow Isotachophoretic Stacking under Field Amplified Conditions

Publisher: American Chemical Society (ACS)

Date: 16-07-2008

DOI: 10.1021/AC8007835

Abstract: An electroosmotic flow (EOF) controlled counterflow isotachophoretic stacking boundary (cf-ITPSB) system under field lified conditions has been examined as a way to improve the sensitivity of anions separated by capillary zone electrophoresis. The system comprised a high concentration of a high-mobility leading ion (100 mM chloride) and a low concentration of low-mobility terminating ion (1-3 mM MES or CHES) added to the s le in an unmodified fused-silica capillary at pH 8.05, buffered with Tris. Computer simulation studies using the software GENTRANS showed an increase in sensitivity of at least 10-fold over the previous cf-ITPSB system for simple inorganic ions, nitrite and nitrate. The simulations also suggested that the cf-ITPSB became stationary within the capillary and that its stationary position was not adversely affected by the concentration of MES. This was in contrast to experimental results that showed a slow and continual movement of the cf-ITPSB. This was more pronounced at lower concentrations of terminator (i.e., <3 mM) and resulted in a loss of resolution due to the cf-ITPSB being closer to the detector upon separation. This discrepancy was attributed to the change in pH across the capillary due to electrolysis and low buffering capacity in the s le, a phenomenon that cannot be simulated by the GENTRANS software. Replacement of MES with CHES as a lower mobility ion with increased buffer capacity failed to reduce the movement of the cf-ITPSB but did provide a further 3-fold improvement in sensitivity. The potential of this approach for sensitivity enhancement was demonstrated for the co-EOF separation of a mixture of six inorganic and small organic ions, with detection limits at the single-figure nanogram per liter level. These detection limits are 100,000 times better than can be achieved by normal hydrodynamic injection (ions prepared in water) and 250 times better than has been achieved by other online preconcentration approaches. The application of the EOF-controlled cf-ITPSB with counter-EOF separation of two pharmaceutical pollutants, naproxen and diflunisal, was also demonstrated with an improvement in sensitivity of 1000 giving detection limits of 350 ng/L in sewage treatment wastewater without any offline pretreatment.

Capillary Electrophoresis: Basic Principles

Publisher: Elsevier

Date: 2012

DOI: 10.1016/B978-0-12-382165-2.00241-5

Hyphenated sample preparation-electrospray and nano-electrospray ionization mass spectrometry for biofluid analysis

Publisher: Elsevier BV

Date: 06-2021

DOI: 10.1016/J.CHROMA.2021.462086

Development of a novel fluorescent tag O-2-[aminoethyl]fluorescein for the electrophoretic separation of oligosaccharides

Publisher: Elsevier BV

Date: 03-2010

DOI: 10.1016/J.ACA.2010.01.011

Abstract: This study describes the development of a novel fluorescent tag, O-2-[aminoethyl]fluorescein, for the separation of sugars by capillary electrophoresis with fluorescence detection using an argon ion laser. The tag was synthesised using three consecutive steps namely: esterification, alkylation and hydrolysis, specifically designed to offer a flexible way in which to make an assortment of fluorescent tags from cheap and readily available starting reagents (typically less than $1 per g of fluorescent tag). Via this flexible synthetic pathway, O-2-[aminoethyl]fluorescein was designed and synthesised with a spacer group to lower steric effects between the fluorescein backbone and the reducing end of the carbohydrate which were anticipated to improve the reactivity of the tag. The newly synthesised tag, O-2-[aminoethyl]fluorescein was evaluated against structurally similar commercial fluorescent motifs namely fluorescent 5-aminomethylfluorescein and non-fluorescent 5-aminofluorescein. Kinetic studies indicated that O-2-[aminoethyl]fluorescein showed similar labeling efficiencies as 5-aminomethylfluorescein, but were achieved in only 30 min, supporting the notion of improved reactivity of the spacer group. The sensitivity of O-2-[aminoethyl]fluorescein was evaluated using maltoheptaose with a detection limit of 1 nM obtained, which was slightly higher than that of 0.3 nM obtained with 5-aminomethylfluorescein, and was due to its lower quantum yield (0.24) when conjugated to the sugar. The separation performance of the tag was also benchmarked with the two commercial reagents using a range of corn syrup oligosaccharides, from 4 to 10 glucose units, typically found in rice starch. Separations were performed using an electrolyte containing 100 mM boric acid, tris at pH 8.65 as background electrolyte, 30 kV applied voltage, 50 microm I.D. x 40 cm (30 cm effective length) capillary. The novel tag showed better resolution of small oligosaccharides, G3 and G4, than the other two reagents, but slightly worse resolution for the longer oligosaccharides, most likely due to the monovalent charge state of the O-2-[aminoethyl]fluorescein compared to the alent charge of the other two tags.

The influence of electrolyte concentration on nanofractures fabricated in a 3D‐printed microfluidic device by controlled dielectric breakdown

Publisher: Wiley

Date: 28-08-2020

DOI: 10.1002/ELPS.202000050

Evaluation of potential cationic probes for the detection of proline and betaine

Publisher: Wiley

Date: 02-11-2014

DOI: 10.1002/ELPS.201400303

Abstract: Osmoregulants are the substances that help plants to tolerate environmental extremes such as salinity and drought. Proline and betaine are two of the most commonly studied osmoregulants. An indirect UV CE method has been developed for simultaneous determination of these osmoregulants. A variety of reported probes and compounds were examined as potential probes for the indirect detection of proline and betaine. Mobility and UV-absorption properties highlighted sulfanilamide as a potential probe for indirect analysis of proline and betaine. Using 5 mM sulfanilamide at pH 2.2 with UV detection at 254 nm, proline and betaine were separated in less than 15 min. The LODs for proline and betaine were 11.6 and 28.3 μM, respectively. The developed method was successfully applied to quantification of these two osmoregulants in spinach and beetroot s les.

Selective extraction and elution of weak bases by in-line solid-phase extraction capillary electrophoresis using a pH step gradient and a weak cation-exchange monolith

Publisher: Royal Society of Chemistry (RSC)

Date: 2008

DOI: 10.1039/B804805C

Abstract: A polymer monolith bearing weak cation-exchange functionality was prepared for the purpose of demonstrating pH-selective extraction and elution in in-line solid-phase extraction-capillary electrophoresis (SPE-CE) utilising a model set of cationic analytes, namely imidazole, lutidine and 3-phenylpropanamine. Optimization of the electrolyte conditions for efficient elution of the adsorbed analytes using a moving pH boundary required that the capillary and monolith be filled with 44 mM sodium acetate at high pH (pH 6) and a low pH electrolyte of 3 mM sodium acetate pH 3 was placed in the electrolyte vials. This combination allowed the adsorbed analytes to be simultaneously eluted and focused into narrow bands, with peak widths of the eluted analytes having a baseline width of 1.2 s immediately after the monolith. Using these optimum elution conditions, the versatility of the SPE-CE approach was demonstrated by removing unwanted adsorbed components after extraction with a wash at a different pH and also by selecting a pH at which only some of the model weak bases were ionised. The analytical performance of the approach was evaluated and the relative standard deviation for peak heights, peak area and migration times were in the ranges of 1.4-5.3, 1.2-3.3 and 0.4-1.2% respectively. Analytes exhibited linear calibrations with r(2) values ranging from 0.996 to 0.999 over two orders of magnitude. Analyte pre-concentration provided excellent sensitivity, and limits of detection for the analyte used in this study were in the range 8.0-30 ng ml(-1), which was an enhancement of 63 when compared to normal hydrodynamic injection occupying 1.3% of the capillary of these bases in water.

Toward a microchip-based solid-phase extraction method for isolation of nucleic acids

Publisher: Wiley

Date: 03-2002

DOI: 10.1002/1522-2683(200203)23:5<727::AID-ELPS727>3.0.CO;2-O

Analysis of phenolic acids by non-aqueous capillary electrophoresis after electrokinetic supercharging

Publisher: Elsevier BV

Date: 11-2010

DOI: 10.1016/J.CHROMA.2010.08.078

Abstract: Electrokinetic supercharging (EKS), a new and powerful on-line preconcentration method for capillary electrophoresis, was utilized in non-aqueous capillary electrophoresis (NACE) to enhance the sensitivity of phenolic acids. The buffer acidity and concentration, leader and terminator length and electrokinetic injection time were optimised, with the optimum conditions being: a background electrolyte of 40 mM Tris-acetic acid (pH 7.9), hydrodynamic injection of 50 mM ammonium chloride (22 s, 0.5 psi) as leader, electrokinetic injection of the s le (180 s, -10 kV), hydrodynamic injection of 20 mM CHES (32 s, 0.5 psi) as terminator, before application of the separation voltage (-25 kV). Under these conditions the sensitivity was enhanced between 1333 and 3440 times when compared to a normal hydrodynamic injection with the s le volume <3% of the capillary volume. Detection limits for the seven phenolic acids were in the range of 0.22-0.51 ng/mL and EKS was found to be 3.6-7.9 times more sensitive than large-volume s le stacking and anion selective exhaustive injection for the same seven phenolic acids.

Unlimited‐volume stacking of ions in capillary electrophoresis. Part 1: Stationary isotachophoretic stacking of anions

Publisher: Wiley

Date: 27-02-2008

DOI: 10.1002/ELPS.200700728

Abstract: An online technique for stacking based on the generation of a stationary isotachophoretic (sITP) boundary is presented. By balancing the anodic migration of an ITP boundary with a cathodic EOF, a stationary boundary is formed that can be used to indefinitely concentrate analytes according to ITP principles during electrokinetic injection. The ITP boundary is created by using an electrolyte containing a leading ion (chloride) and a suitable terminating ion added to the s le (2-morpholinoethanesulphonic acid, MES). Destacking and separation are achieved simply by replacement of the s le vial with electrolyte. The formation and stabilisation of the sITP boundary were evaluated through computer simulation which revealed that the pH had little impact upon the formation of the sITP boundary, but did govern the position at which it becomes stationary. Simulations also demonstrated that similar results were obtained when the capillary was initially filled with s le/terminator or leader/electrolyte, which was also supported by experimental results. Using 100 mM Cl(-), 200 mM Tris, pH 8.05 as the leader/electrolyte and adding 100 mM MES, 200 mM Tris, pH 8.05 to the s le, the sITP boundary was established after 5 min at -20 kV and was stable for at least 60 min. This provided detection limits for NO(2) (-), NO(3) (-) and SCN(-) of 0.05-0.66 ppb, which are 10,000 times lower than hydrodynamic injection and 10-50 times lower than other stacking approaches used for these inorganic ions.

Characterization of Wear Mechanisms of Silicon Carbide Materials

Publisher: Trans Tech Publications Ltd

Date: 27-10-2010

DOI: 10.4028/WWW.SCIENTIFIC.NET/AST.64.49

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.

In Silico Screening of Two-Dimensional Separation Selectivity for Ion Chromatography × Capillary Electrophoresis Separation of Low-Molecular-Mass Organic Acids

Publisher: American Chemical Society (ACS)

Date: 24-08-2017

DOI: 10.1021/ACS.ANALCHEM.7B01187

Abstract: A prerequisite for ordered two-dimensional (2D) separations and full utilization of the enhanced 2D peak capacity is selective exploitation of the s le attributes, described as s le dimensionality. In order to take s le dimensionality into account prior to optimization of a 2D separation, a new concept based on construction of 2D separation selectivity maps is proposed and demonstrated for ion chromatography × capillary electrophoresis (IC×CE) separation of low-molecular-mass organic acids as test analytes. For this purpose, 1D separation selectivity maps were constructed based on calculation of pairwise separation factors and identification of critical pairs for four IC stationary phases and 28 levels of background electrolyte pH in CE. The derived IC and CE maps were then superimposed and the effectiveness of the respective 2D separations assessed using an in silico approach, followed by testing ex les of one successful and one unsuccessful 2D combination experimentally. The results confirmed the efficacy of the predictions, which require a minimal number of experiments compared to the traditional one-at-a-time approach. Following the same principles, the proposed framework can also be adapted for optimization of separation selectivity in various 2D combinations and for other applications.

Magnetism-Assisted Density Gradient Separation of Microplastics

Publisher: American Chemical Society (ACS)

Date: 05-12-2022

DOI: 10.1021/ACS.ANALCHEM.2C04001

One step multi-material 3D printing for the fabrication of a photometric detector flow cell

Publisher: Elsevier BV

Date: 02-2020

DOI: 10.1016/J.ACA.2019.10.075

Abstract: Optical detection is the most common detection mode for many analytical assays. Photometric detection systems and their integration with analytical systems usually require several assembly parts and manual alignment of the capillary/tubing which affects sensitivity and repeatability. 3D printing is an innovative technology for the fabrication of integrated complex detection systems. One step multi-material 3D printing has been explored to fabricate a photometric detector flow cell from optically transparent and opaque materials using a dual-head FDM 3D printer. Integration of the microchannel, the detection window and the slit in a single device eliminates the need for manual alignment of fluidic and optical components, and hence improves sensitivity and repeatability. 3D printing allowed for rapid design optimisation by varying the slit dimension and optical pathlength. The optimised design was evaluated by determining stray light, effective path length and the signal to noise ratio using orange G. The optimised flow cell with extended path length of 10 mm and 500 μm slit yielded 0.02% stray light, 89% effective path length and detection limit of 2 nM. The sensitivity was also improved by 80% in the process of optimisation, using a blue 470 nm LED as a light source.

Thread based electrofluidic platform for direct metabolite analysis in complex samples

Publisher: Elsevier BV

Date: 02-2018

DOI: 10.1016/J.ACA.2017.10.029

Abstract: The application of electrophoresis upon commercial threads is investigated for development of low-cost diagnostics assays, designed for the matrix separation and quantification of low abundance metabolites in complex s les - in this work riboflavin in human urine. Zone electrophoresis was evaluated upon 8 commercially available threads, with several synthetic threads exhibiting higher electroosmotic flow (EOF) and increased electrophoretic mobility of the rhodamine 6G, rhodamine B, and fluorescein. Of those tested, a nylon bundle was selected as the best platform, offering less band dispersion and higher resolution, a high relative EOF, whilst minimising the contribution of joule heating. A novel 3D printed platform was designed, based on a modular system, facilitating the electrophoresis process and rapid assembly, whilst offering the potential for multiplexed analysis or investigation of more complex systems. Using the thread-based electrophoresis system, riboflavin was determined in less than 2 min. The device exhibited a linear working range from 0.1 to 15 μg/mL of riboflavin in urine, and was in good agreement with capillary electrophoresis measurements.

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.

Determination of food grade antioxidants using microemulsion electrokinetic chromatography

Publisher: Wiley

Date: 30-06-2010

DOI: 10.1002/ELPS.201000050

Abstract: Seven food grade antioxidants were resolved by microemulsion electrokinetic chromatography. The antioxidants included propyl gallate, octyl gallate, dodecyl gallate, butylated hydroxyanisole, butylated hydroxytoluene, tert-butylhydroquinone and alpha-tocopherol. They were resolved in 11 min using a low pH microemulsion containing 20% propan-2-ol. Theoretical plates in the range 39,000-95,000 per length of column (38.5 cm) were recorded for the antioxidants. The LODs were calculated to be in the range 9-44 microg/mL (30 s hydrostatic injection and a 50 microm id capillary column). The method can also be used to simultaneously analyse for the synthetic preservatives sorbic acid, benzoic acid, salicylic acid and the parabens. The method was successfully applied to noodles for the determination of butylated hydroxytoluene and propyl gallate and to pharmaceutical supplement tablets for alpha-tocopherol. The in-capillary concentration of butylated hydroxytoluene by sweeping was also demonstrated.

Toward optimization of macroporous silica gels for application to capillary or microchip-based CEC and LC

Publisher: Elsevier BV

Date: 12-2004

DOI: 10.1016/J.JNONCRYSOL.2004.06.028

Utilisation of pH stacking in conjunction with a highly absorbing chromophore, 5-aminofluorescein, to improve the sensitivity of capillary electrophoresis for carbohydrate analysis

Publisher: Elsevier BV

Date: 07-2008

DOI: 10.1016/J.CHROMA.2008.04.022

Abstract: This study explores the use of pH stacking in conjunction with 5-aminofluorescein as a derivatization agent for the sensitive analysis of simple sugars such as glucose, lactose and maltotriose by capillary electrophoresis (CE). The derivatization agent was selected on the basis of its extremely high molar absorptivity, its compatibility with a 488nm light-emitting diode (LED) and the fact that it has two ionizable groups making it compatible with on-line stacking using a dynamic pH junction. The influence of both acetic and formic acids at concentrations of 0.19, 0.019 and 0.0019molL(-1) were investigated with regard to both derivatization efficiency and the ability to stack using a dynamic pH junction. Superior sensitivity and resolution was obtained in formic acid over acetic acid. Substantially lower peaks were obtained with 0.19molL(-1) formic acid when compared to 0.019 and 0.0019molL(-1) concentrations, which was confirmed by computer simulation studies to be due to the inadequate movement of the pH boundary for stacking. Further simulation studies combined with experimental data showed the separation with the best resolution and greatest sensitivity when the carbohydrates were derivatized with the 0.095molL(-1) formic acid. Utilisation of stacking via dynamic pH junction mode in conjunction with LED detection enabled efficiencies of 150,000 plates and detection limits in the order of 8.5x10(-8)molL(-1) for simple sugars such as glucose, lactose and maltotriose hydrate. The current system also demonstrates a 515 times improvement in sensitivity when compared to using a normal deuterium l , and 16 times improvement over other systems using LEDs.

Ion chromatography on-chip

Publisher: Elsevier BV

Date: 07-2001

DOI: 10.1016/S0021-9673(01)00855-X

Abstract: On-chip separation of inorganic anions by ion-exchange chromatography was realized. Micro separation channels were fabricated on a silicon wafer and sealed with a Pyrex cover plate using standard photolithography, wet and dry chemical etching, and anodic bonding techniques. Quaternary ammonium latex particles were employed for the first time to coat the separation channels on-chip. Owing to the narrow depths of the channels on the chip, 0.5-10 microm, there were more interactions of the analytes with the stationary phase on the chip than in a 50-microm I.D. capillary. With off-chip injection (20 nl) and UV detection, NO2-, NO3-, I-, and thiourea were separated using 1 mM KCl as the eluent. The linear ranges for NO2- and NO3- are from 5 to 1000 microM with the detection limits of 0.5 microM.

One-Step Fabrication of a Microfluidic Device with an Integrated Membrane and Embedded Reagents by Multimaterial 3D Printing

Publisher: American Chemical Society (ACS)

Date: 05-04-2017

DOI: 10.1021/ACS.ANALCHEM.7B00409

Abstract: One of the largest impediments in the development of microfluidic-based smart sensing systems is the manufacturability of integrated, complex devices. Here we propose multimaterial 3D printing for the fabrication of such devices in a single step. A microfluidic device containing an integrated porous membrane and embedded liquid reagents was made by 3D printing and applied for the analysis of nitrate in soil. The manufacture of the integrated, sealed device was realized as a single print within 30 min. The body of the device was printed in transparent acrylonitrile butadiene styrene (ABS) and contained a 400 μm wide structure printed from a commercially available composite filament. The composite filament can be turned into a porous material through dissolution of a water-soluble material. Liquid reagents were integrated by briefly pausing the printing before resuming for sealing the device. The devices were evaluated by the determination of nitrate in a soil slurry containing zinc particles for the reduction of nitrate to nitrite using the Griess reagent. Using a consumer digital camera, the linear range of the detector response ranged from 0 to 60 ppm, covering the normal range of nitrate in soil. To ensure that the sealing of the reagent chamber is maintained, aqueous reagents should be avoided. When using the nonaqueous reagent, the multimaterial device containing the Griess reagent could be stored for over 4 days but increased the detection range to 100-500 ppm. Multimaterial 3D printing is a potentially new approach for the manufacture of microfluidic devices with multiple integrated functional components.

Biphasic Magnetic Levitation to Detect Organic Pollutants on Microplastics

Publisher: American Chemical Society (ACS)

Date: 17-05-2022

DOI: 10.1021/ACS.ANALCHEM.2C01094

Abstract: Microplastics have the potential to adsorb organic pollutants due to their lipophilic nature. Evaluating the distribution of multiple organic pollutants in different types of microplastics coexisting in a s le is a strenuous and challenging analytical task. Here, we report position-dependent microplastic trapping in a biphasic medium comprising a paramagnetic aqueous donor phase containing the mixed microplastics and a diamagnetic organic acceptor phase. Depending on the relative height of the s le container positioned in a magnetic field, the selective density-dependent trapping of microplastics is achieved. Concurrently, the organic pollutants adsorbed on the microplastics are desorbed in the organic acceptor phase, which is easily solidified, separated, and transferred for organic pollutant determination by high-performance liquid chromatography. This facilitates analytical studies involving multiple organic pollutants distributed in solid heterogeneous mixtures.

Dry film microchips for miniaturised separations

Publisher: Wiley

Date: 12-2009

DOI: 10.1002/ELPS.200900233

Abstract: In this work microfluidic devices were made from the dry film photoresist Ordyl SY330, characterised by optical and electron microscopy and used for electrophoretic separations. A simple and fast microfabrication process was developed for the fabrication of channels that are 50 microm wide and 30 microm in height, requiring only the use of an office laminator, a hot plate, an exposure source and mask and an electric drill to make four microdevices in less than 1 h. The optical properties of the photoresist were studied and the resist showed significant absorbance below 370 nm and 570-630 nm, and had an optical transmission of 80% between 400 and 550 nm. Fluorescence emission over the region of maximum transmission was low allowing these devices to be used for fluorescence detection at 488/512 nm. Electrophoretic separation of APTS and three derivatised sugars was performed in 20 mM phosphate buffer, pH 2.5 with efficiencies of the three sugars of 40,000 plates (2,100,000 plates/m) within 30 s at a field strength of 500 V/cm. The simple fabrication process also allowed microchannels to be easily filled with chromatography particles before sealing, avoiding the challenging task of slurry packing, and the potential of these devices for liquid chromatography was demonstrated by the extraction of fluorescein onto anion exchange particles.

University Of Tasmania

Location: Australia

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Discovery Projects - Grant ID: DP210102928

Start Date: 2021

End Date: 12-2024

Amount: $300,000.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP210100343

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End Date: 04-2027

Amount: $478,589.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP220100252

Start Date: 2023

End Date: 12-2026

Amount: $799,084.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE110100041

Start Date: 02-2011

End Date: 12-2011

Amount: $240,000.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP160101247

Start Date: 10-2017

End Date: 12-2021

Amount: $630,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0453223

Start Date: 2004

End Date: 04-2008

Amount: $293,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0984745

Start Date: 2009

End Date: 12-2013

Amount: $705,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP210101466

Start Date: 03-2021

End Date: 03-2025

Amount: $517,000.00

Funder: Australian Research Council

ARC Future Fellowships - Grant ID: FT130100101

Start Date: 2014

End Date: 12-2019

Amount: $871,645.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE230100078

Start Date: 2023

End Date: 12-2023

Amount: $731,584.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP140100858

Start Date: 10-2014

End Date: 06-2020

Amount: $600,000.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE0668471

Start Date: 2006

End Date: 12-2006

Amount: $262,706.00

Funder: Australian Research Council

Industrial Transformation Training Centres - Grant ID: IC140100022

Start Date: 10-2014

End Date: 06-2019

Amount: $2,148,935.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0666121

Start Date: 03-2006

End Date: 12-2009

Amount: $180,000.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP0669302

Start Date: 09-2006

End Date: 08-2010

Amount: $530,000.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP0776804

Start Date: 2007

End Date: 12-2008

Amount: $59,626.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE0989491

Start Date: 2009

End Date: 12-2009

Amount: $172,025.00

Funder: Australian Research Council