Rosanne Guijt

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.

Blood apheresis technologies – a critical review on challenges towards efficient blood separation and treatment

Publisher: Royal Society of Chemistry (RSC)

Date: 2021

DOI: 10.1039/D1MA00859E

Abstract: This review article critically assesses materials engineering advances across blood separation technologies which addresses operating challenges such as surface fouling and material biocompatibility.

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.

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

Chemical and physical processes for integrated temperature control in microfluidic devices

Publisher: Royal Society of Chemistry (RSC)

Date: 2003

DOI: 10.1039/B210629A

Abstract: Microfluidic devices are a promising new tool for studying and optimizing (bio)chemical reactions and analyses. Many (bio)chemical reactions require accurate temperature control, such as for ex le thermocycling for PCR. Here, a new integrated temperature control system for microfluidic devices is presented, using chemical and physical processes to locally regulate temperature. In demonstration experiments, the evaporation of acetone was used as an endothermic process to cool a microchannel. Additionally, heating of a microchannel was achieved by dissolution of concentrated sulfuric acid in water as an exothermic process. Localization of the contact area of two flows in a microfluidic channel allows control of the position and the magnitude of the thermal effect.

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.

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.

New approaches for fabrication of microfluidic capillary electrophoresis devices with on-chip conductivity detection

Publisher: Wiley

Date: 2001

DOI: 10.1002/1522-2683(200101)22:2<235::AID-ELPS235>3.0.CO;2-O

Plant leaves as templates for soft lithography

Publisher: Royal Society of Chemistry (RSC)

Date: 2016

DOI: 10.1039/C5RA25890A

Abstract: Complex microvascular venation patterns of natural leaves are replicated into PDMS replicas, which allows for a leakage-tight seal with a flat substrate despite the surface topography.

Lab on a Chip – Future Technology for Characterizing Biotechnology Products

Publisher: Elsevier

Date: 2011

DOI: 10.1016/B978-0-08-088504-9.00133-1

An improved nucleic acid sequence-based amplification method mediated by T4 gene 32 protein

Publisher: Public Library of Science (PLoS)

Date: 24-03-2022

DOI: 10.1371/JOURNAL.PONE.0265391

Abstract: The uptake of Nucleic Acid Sequence-Based Amplification (NASBA) for point of care testing may be hindered by a complexity in the workflow due the requirement of a thermal denaturation step to initiate the cyclic isothermal lification before the addition of the lification enzymes. Despite reports of successful enhancement of other DNA and RNA lification methods using DNA and RNA binding proteins, this has not been reported for NASBA. Here, three single-stranded binding proteins, RecA, Extreme Thermostable Single-stranded binding protein (ET SSB) and T4 gene gp32 protein (gp32), were incorporated in NASBA protocol and used for single pot, one-step NASBA at 41 °C. Indeed, all SSBs showed significantly improved lifications compared with the 2-step process, but only gp32 showed no non-specific aberrant lification, and slightly improved the time-to-positivity in comparison with the conventional NASBA. For synthetic HIV-1 RNA, gp32 was found to improve the time-to-positivity (ttp) by average of 13.6% of one-step NASBA and 6.7% of conventional NASBA for the detection of HIV-1 RNA, showing its potential for simplifying the workflow as desirable for point of care applications of NASBA.

3D printing for the integration of porous materials into miniaturised fluidic devices: A review

Publisher: Elsevier BV

Date: 11-2021

DOI: 10.1016/J.ACA.2021.338796

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.

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.

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.

Capillary electrophoresis with on-chip four-electrode capacitively coupled conductivity detection for application in bioanalysis

Publisher: Wiley

Date: 07-2001

DOI: 10.1002/1522-2683(200107)22:12<2537::AID-ELPS2537>3.0.CO;2-C

Palladium-mediated organic synthesis using porous polymer monolith formed in situ as a continuous catalyst support structure for application in microfluidic devices

Publisher: Elsevier BV

Date: 02-2009

DOI: 10.1016/J.TET.2008.12.007

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.

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.

Recent developments in digital light processing 3D-printing techniques for microfluidic analytical devices

Publisher: Elsevier BV

Date: 03-2023

DOI: 10.1016/J.CHROMA.2023.463842

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.

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.

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.

Use of bioaffinity interactions in electrokinetically controlled assays on microfabricated devices

Publisher: Wiley

Date: 03-2002

DOI: 10.1002/1522-2683(200203)23:6<823::AID-ELPS823>3.0.CO;2-Z

Direct coupling of a free-flow isotachophoresis (FFITP) device with electrospray ionization mass spectrometry (ESI-MS)

Publisher: Royal Society of Chemistry (RSC)

Date: 2015

DOI: 10.1039/C5LC00523J

Abstract: The direct coupling of free-flow isotachophoresis device with an electrospray-ionization-mass-spectrometer allows continuous online detection without any s le preparation such as purification and labeling.

Internal electrolyte temperatures for polymer and fused-silica capillaries used in capillary electrophoresis

Publisher: Wiley

Date: 11-2005

DOI: 10.1002/ELPS.200500346

Abstract: Polymers are important as materials for manufacturing microfluidic devices for electrodriven separations, in which Joule heating is an unavoidable phenomenon. Heating effects were investigated in polymer capillaries using a CE setup. This study is the first step toward the longer-term objective of the study of heating effects occurring in polymeric microfluidic devices. The thermal conductivity of polymers is much smaller than that of fused silica (FS), resulting in less efficient dissipation of heat in polymeric capillaries. This study used conductance measurements as a temperature probe to determine the mean electrolyte temperatures in CE capillaries of different materials. Values for mean electrolyte temperatures in capillaries made of New Generation FluoroPolymer (NGFP), poly-(methylmethacrylate) (PMMA), and poly(ether ether ketone) (PEEK) capillaries were compared with those obtained for FS capillaries. Extrapolation of plots of conductance versus power per unit length (P/L) to zero power was used to obtain conductance values free of Joule heating effects. The ratio of the measured conductance values at different power levels to the conductance at zero power was used to determine the mean temperature of the electrolyte. For each type of capillary material, it was found that the average increase in the mean temperature of the electrolyte (DeltaT(Mean)) was directly proportional to P/L and inversely proportional to the thermal conductivity (lambda) of the capillary material. At 7.5 W/m, values for DeltaT(Mean) for NGFP, PMMA, and PEEK were determined to be 36.6, 33.8, and 30.7 degrees C, respectively. Under identical conditions, DeltaT(Mean) for FS capillaries was 20.4 degrees C.

UV initiated formation of polymer monoliths in glass and polymer microreactors

Publisher: Elsevier BV

Date: 07-2011

DOI: 10.1016/J.SNB.2010.11.020

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.

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

Development of a pumpless acoustofluidic device for rapid food pathogen detection

Publisher: Elsevier BV

Date: 09-2023

DOI: 10.1016/J.ACA.2023.341581

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.

Lab on a Chip – Future Technology for Characterizing Biotechnology Products

Publisher: Elsevier

Date: 2017

DOI: 10.1016/B978-0-12-809633-8.09103-2

3D printed integrated nanoporous membranes for electroextraction of DNA

Publisher: Royal Society of Chemistry (RSC)

Date: 2023

DOI: 10.1039/D2NR07178A

Abstract: 3D printed functionally integrated device containing nanoporous membranes with properties tailored for the electroextraction of DNA.

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.

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.

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.

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.

Miniaturised total chemical-analysis systems (μTAS) that periodically convert chemical into electronic information

Publisher: Elsevier BV

Date: 11-2018

DOI: 10.1016/J.SNB.2018.06.054

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

Versatile electrophoresis‐based self‐test platform

Publisher: Wiley

Date: 03-2015

DOI: 10.1002/ELPS.201500044

Abstract: Lab on a Chip technology offers the possibility to extract chemical information from a complex s le in a simple, automated way without the need for a laboratory setting. In the health care sector, this chemical information could be used as a diagnostic tool for ex le to inform dosing. In this issue, the research underpinning a family of electrophoresis-based point-of-care devices for self-testing of ionic analytes in various s le matrices is described [Electrophoresis 2015, 36, 712-721.]. Hardware, software, and methodological chances made to improve the overall analytical performance in terms of accuracy, precision, detection limit, and reliability are discussed. In addition to the main focus of lithium monitoring, new applications including the use of the platform for veterinary purposes, sodium, and for creatinine measurements are included.

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.

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.

A review on the sources, occurrence and health risks of per-/poly-fluoroalkyl substances (PFAS) arising from the manufacture and disposal of electric and electronic products

Publisher: Elsevier BV

Date: 12-2020

DOI: 10.1016/J.JWPE.2020.101683

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.

Facile fabrication of micro-/nanostructured, superhydrophobic membranes with adjustable porosity by 3D printing

Publisher: Royal Society of Chemistry (RSC)

Date: 2021

DOI: 10.1039/D1TA03352B

Abstract: 3D printed micro/-nanostructured thin membranes with inherent adjustable porosity in the submicron range for the use as water–oil separators.

Abridged solid-phase extraction with alkaline Poly(ethylene) glycol lysis (ASAP) for direct DNA amplification

Publisher: Elsevier BV

Date: 2024

DOI: 10.1016/J.TALANTA.2023.125006

Temperature profiles and heat dissipation in capillary electrophoresis

Publisher: American Chemical Society (ACS)

Date: 24-02-2006

DOI: 10.1021/AC052075X

Abstract: While temperature control is usually employed in capillary electrophoresis (CE) to aid heat dissipation and provide acceptable precision, internal electrolyte temperatures are almost never measured. In principle, this limits the accuracy, repeatability, and method robustness. This work presents a fundamental study that combines the development of new equations characterizing temperature profiles in CE with a new method of temperature determination. New equations were derived from first principles relating the mean, axial, and inner wall electrolyte temperatures (T(Mean), T(Axis), T(Wall)). T(Mean) was shown to occur at a distance 1/ radical3 times the internal radius of the capillary from the center of the capillary and to be a weighted average of (2/3)T(Axis) and (1/3)T(Wall). Conductance (G) and electroosmotic mobility (mu(EOF)) can be used to determine T(Mean) and T(Wall), respectively. Extrapolation of curves of mu(EOF) versus power per unit length (P/L) at different temperatures was used to calibrate the variation of mu(EOF) with temperature (T), free from Joule heating effects. mu(EOF) increased at 2.22%/ degrees C. The experimentally determined temperatures using mu(EOF) agreed to within 0.2 degrees C with those determined using G. The accuracy of G measurements was confirmed independently by measuring the electrical conductivity (kappa) of the bulk electrolyte over a range of temperatures and by calculating the variation of G with T from the Debye-Hückel-Onsager equation. T(Mean) was found to be up to 20 degrees C higher than the external temperature under typical conditions using active air-cooling and a 74.0-microm-internal diameter (di) fused-silica capillary. A combination of experimentally determined and calculated temperatures enables a complete temperature profile for a fused-silica capillary to be drawn and the thickness of the stationary air layer to be determined. As an ex le, at P/L = 1.00 Wm(-1), the determined radial temperature difference across the electrolyte was 0.14 degrees C the temperature difference across the fused-silica wall was 0.17 degrees C, across the poly(imide) coating was 0.13 degrees C, and across the stationary air layer was 2.33 degrees C.

On-Chip Contactless Four-Electrode Conductivity Detection for Capillary Electrophoresis Devices

Publisher: American Chemical Society (ACS)

Date: 14-12-2002

DOI: 10.1021/AC0157371

Abstract: In this contribution, a capillary electrophoresis microdevice with an integrated on-chip contactless four-electrode conductivity detector is presented. A 6-cm-long, 70-microm-wide, and 20-microm-deep channel was etched in a glass substrate that was bonded to a second glass substrate in order to form a sealed channel. Four contactless electrodes (metal electrodes covered by 30-nm silicon carbide) were deposited and patterned on the second glass substrate for on-chip conductivity detection. Contactless conductivity detection was performed in either a two- or a four-electrode configuration. Experimental results confirmed the improved characteristics of the four-electrode configuration over the classical two-electrode detection setup. The four-electrode configuration allows for sensitive detection for varying carrier-electrolyte background conductivity without the need for adjustment of the measurement frequency. Reproducible electrophoretic separations of three inorganic cations (K+, Na+, Li+) and six organic acids are presented. Detection as low as 5 microM for potassium was demonstrated.

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

Recent advances in affinity capillary electrophoresis

Publisher: Wiley

Date: 12-2000

DOI: 10.1002/1522-2683(200012)21:18<3905::AID-ELPS3905>3.0.CO;2-4

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.

Amplification-free electrochemiluminescence molecular beacon-based microRNA sensing using a mobile phone for detection

Publisher: Elsevier BV

Date: 03-2021

DOI: 10.1016/J.SNB.2020.129261

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

Variation of zeta-potential with temperature in fused-silica capillaries used for capillary electrophoresis

Publisher: Wiley

Date: 02-2006

DOI: 10.1002/ELPS.200500566

Abstract: The temperature variation of electroosmotic mobility corrected for the effects of Joule heating (muEOF0) was employed to investigate the variation of the zeta-potential (zeta) with temperature in fused-silica capillaries. Experimentally determined values for zeta increased at 0.39% per degrees C, a rate that is about four to five times smaller than reported previously. Experimentally determined values of zeta were directly proportional to the absolute temperature although values were also influenced slightly by changes to the dielectric constant. It was found that the effective charge density at the inner surface of the capillary was independent of temperature.

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

Considerations on contactless conductivity detection in capillary electrophoresis

Publisher: Wiley

Date: 09-2002

DOI: 10.1002/1522-2683(200209)23:17<2888::AID-ELPS2888>3.0.CO;2-4

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

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.

A Simple Electrochemical Swab Assay for the Rapid Quantification of Clonazepam in Unprocessed Saliva Enabled by Lubricin Antifouling Coatings

Publisher: Wiley

Date: 07-2020

DOI: 10.1002/CELC.202000393

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

Microfluidic Device for Studying Traumatic Brain Injury

Publisher: Springer New York

Date: 2017

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

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.

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.

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.

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

Erratum: Temperature profiles and heat dissipation in capillary electrophoresis (Analytical Chemistry (2006) 78, (2684-2693))

Publisher: American Chemical Society (ACS)

Date: 07-03-2007

DOI: 10.1021/AC070216K

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.

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.

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.

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.

Miniaturized analytical assays in biotechnology

Publisher: Elsevier BV

Date: 08-2003

DOI: 10.1016/S0734-9750(03)00059-4

Abstract: Biotechnology today is a well-established paradigm in many areas of human endeavor, such as the pharmaceutical industry, agriculture, management of the environment and many others. Meanwhile, biology is undergoing a spectacular transition: whereas systematic biology was replaced gradually by molecular biology, the latter is rapidly being transformed into a new systematic era in which entire genomes are being charted by ever more sophisticated analytical techniques. In the wake of this onslaught of data, new fields are germinating, such as bioinformatics in an attempt to find answers to fundamental questions, answers that may be hidden in the massive amounts of data already available today.

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

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

Colour tuning and enhancement of gel-based electrochemiluminescence devices utilising Ru(ii) and Ir(iii) complexes

Publisher: Royal Society of Chemistry (RSC)

Date: 2019

DOI: 10.1039/C9CC05031K

Abstract: Combining luminophores in ratios that compensate for energy transfer provides a range of new emission colours for gel-based electrochemiluminescence devices.

Determination of inorganic ions using microfluidic devices

Publisher: Wiley

Date: 11-2004

DOI: 10.1002/ELPS.200406120

Abstract: The separation and detection of inorganic ions on microfluidic devices has received little attention since the ‘lab‐on‐a‐chip’ concept has revolutionised the field of electrokinetically driven analysis. This review presents a summary and discussion of the published literature on inorganic analysis using microfluidic devices and includes sections on electromigration separation methods, namely isotachophoresis (ITP), capillary electrophoresis (CE), and hyphenated ITP‐CE, together with a brief account of flow injection analysis. The review concludes with the authors' perspective on future directions for inorganic analysis on microfluidic devices.

Fabrication of a glass-implemented microcapillary electrophoresis device with integrated contactless conductivity detection

Publisher: Wiley

Date: 10-2002

DOI: 10.1002/1522-2683(200210)23:20<3511::AID-ELPS3511>3.0.CO;2-C

Reliable electrophoretic mobilities free from Joule heating effects using CE

Publisher: Wiley

Date: 10-2007

DOI: 10.1002/ELPS.200700343

Abstract: Ionic electrophoretic mobilities determined by means of CE experiments are sometimes different when compared to generally accepted values based on limiting ionic conductance measurements. While the effect of ionic strength on electrophoretic mobility has been long understood, the increase in the mobility that results from Joule heating (the resistive heating that occurs when a current passes through an electrolyte) has been largely overlooked. In this work, a simple method for obtaining reliable and reproducible values of electrophoretic mobility is described. The electrophoretic mobility is measured over a range of driving powers and the extrapolation to zero power dissipation is employed to eliminate the effect of Joule heating. These extrapolated values of electrophoretic mobility can then be used to calculate limiting ionic mobilities by making a correction for ionic strength this somewhat complicated calculation is conveniently performed by using the freeware program PeakMaster 5. These straightforward procedures improve the agreement between experimentally determined and literature values of limiting ionic mobility by at least one order of magnitude. Using Tris-chromate BGE with a value of conductivity 0.34 S/m and ionic strength 59 mM at a modest dissipated power per unit length of 2.0 W/m, values of mobility for inorganic anions were increased by an average of 12.6% relative to their values free from the effects of Joule heating. These increases were accompanied by a reduction in mobilities due to the ionic strength effect, which was 11% for univalent and 28% for alent inorganic ions compared to their limiting ionic mobilities. Additionally, it was possible to determine the limiting ionic mobility for a number of aromatic anions by using PeakMaster 5 to perform an ionic strength correction. A major significance of this work is in being able to use CE to obtain reliable and accurate values of electrophoretic mobilities with all its benefits, including understanding and interpretation of physicochemical phenomena and the ability to model and simulate such phenomena accurately.

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.

Van de Graaff generator for capillary electrophoresis

Publisher: Elsevier BV

Date: 09-2017

DOI: 10.1016/J.CHROMA.2017.08.026

Abstract: A new approach for high voltage capillary electrophoresis (CE) is proposed, which replaces the standard high voltage power supply with a Van de Graaff generator, a low current power source. Because the Van de Graaff generator is a current-limited source (10μA), potentials exceeding 100kV can be generated for CE when the electrical resistance of the capillary is maximized. This was achieved by decreasing the capillary diameter and reducing the buffer ionic strength. Using 2mM borate buffer and a 5μm i.d. capillary, fluorescently labeled amino acids were separated with efficiencies up to 3.5 million plates a 5.7 fold improvement in separation efficiency compared to a normal power supply (NPS) typically used in CE. This separation efficiency was realized using a simple set-up without significant Joule heating, making the Van de Graaff generator a promising alternative for applying the high potentials required for enhancing resolution in the separation and analysis of highly complex s les, for ex le mixtures of glycans.

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.

Capillary Electrophoresis: Basic Principles

Publisher: Elsevier

Date: 2012

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

Closed-loop control systems for pumps used in portable analytical systems

Publisher: Elsevier BV

Date: 04-2023

DOI: 10.1016/J.CHROMA.2023.463931

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

Indirect Electro-Osmotic Pumping

Publisher: SAGE Publications

Date: 06-2002

DOI: 10.1016/S1535-5535(04)00195-9

Determination of the surface heat-transfer coefficient in CE

Publisher: Wiley

Date: 03-2200

DOI: 10.1002/ELPS.200800647

Abstract: A knowledge of the heat-transfer coefficient, h(s), for the external surface of the capillary or the overall heat coefficient, h(OA), is of great value in predicting the mean increase in temperature of the electrolyte, DeltaT(Mean), during electrokinetic separations. For CE, traditional indirect methods of determining h(s) were time-consuming and tended to overestimate cooling efficiency a novel method is introduced, which is based on curve-fitting of plots of conductance versus voltage to calculate several important parameters including DeltaT(Mean), h(s), the conductance free of Joule heating effects (G(0)) and the voltage that causes autothermal runaway, V(lim). The new method is superior to previously published methods in that it can be performed more quickly and that it corrects for systematic errors in the measurement of electric current for voltages <5 kV. These errors tended to exaggerate the cooling efficiency of commercial instruments so that the calculated increases in electrolyte temperature were smaller than their actual values. Axially averaged values for h(s) were determined for three different commercial CE instruments ranging from 164 W m(-2) K(-1) for a passively cooled instrument in a drafty environment to 460 W m(-2) K(-1) for a liquid-cooled instrument.

3D Printing Functionally Graded Porous Materials for Simultaneous Fabrication of Dense and Porous Structures in Membrane‐Integrated Fluidic Devices

Publisher: Wiley

Date: 17-01-2023

DOI: 10.1002/SSTR.202200314

Abstract: 3D printing provides access to complex multilevel architectures, though the capability to routinely print and integrate structures of controlled porosity is limited. Herein, grayscale digital light projection 3D printing of a polymerization‐induced phase separation ink is introduced to directly 3D print functionally graded porous within a single layer from the same ink formulation. The structural properties of materials printed from a single ink are tuned from an effectively dense to a porous material with interconnected pores up to 250 nm. Heterostructures with the physically dense structure of porosity 0.8% and porous structures with up to 23% can be concurrently formed within a layer, with high spatial resolution inherent of this 3D printing technique. Materials with densities from 1.01 to 1.21 g cm −3 are 3D printed in a wicking device and show wicking rates (H 2 O) from complete diffusion blockage up to 4.5 mm h −1 . Furthermore, a proof‐of‐concept membrane‐integrated fluidic device is used for the elemental metal sensing of iron in soil. The presented single‐step fabrication of functionally graded materials with pixel‐based control within a single layer holds potential for manufacturing and integrating membranes or sorbents for environmental, biotechnology, and healthcare applications.

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.

Conductivity detection for conventional and miniaturised capillary electrophoresis systems

Publisher: Wiley

Date: 12-2004

DOI: 10.1002/ELPS.200406156

Abstract: Since the introduction of capillary electrophoresis (CE), conductivity detection has been an attractive means of detection. No additional chemical properties are required for detection, and no loss in sensitivity is expected when miniaturising the detector to scale with narrow‐bore capillaries or even to the microchip format. Integration of conductivity and CE, however, involves a challenging combination of engineering issues. In conductivity detection the resistance of the solution is most frequently measured in an alternating current (AC) circuit. The influence of capacitors both in series and in parallel with the solution resistance should be minimised during conductivity measurements. For contact conductivity measurements, the positioning and alignment of the detection electrodes is crucial. A contact conductivity detector for CE has been commercially available, but was withdrawn from the market. Microfabrication technology enables integration and precise alignment of electrodes, resulting in the popularity of conductivity detection in microfluidic devices. In contactless conductivity detection, the alignment of the electrodes with respect to the capillary is less crucial. Contactless conductivity detection (CCD) was introduced in capillary CE, and similar electronics have been applied for CCD using planar electrodes in microfluidic devices. A contactless conductivity detector for capillaries has been commercialised recently. In this review, different approaches towards conductivity detection in capillaries and chip‐based CE are discussed. In contrast to previous reviews, the focus of the present review is on the technological developments and challenges in conductivity detection in CE.

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

Macroporous monolith supports for continuous flow capillary microreactors

Publisher: Elsevier BV

Date: 12-2006

DOI: 10.1016/J.TETLET.2006.10.113

3D Printing: An Alternative Microfabrication Approach with Unprecedented Opportunities in Design

Publisher: American Chemical Society (ACS)

Date: 02-12-2021

DOI: 10.1021/ACS.ANALCHEM.0C04672

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.

Microfluidic devices for flow-through supported palladium catalysis on porous organic monolith

Publisher: CSIRO Publishing

Date: 2008

DOI: 10.1071/CH08160

Abstract: Flow-through microreactors are described, constructed of fused silica capillaries with an internal diameter of 100 μm and glass microchips with a channel dimension of 150 μm and involving the in situ UV-initiated synthesis of a poly(glycidyl methacrylate-co-ethylene dimethacrylate) porous polymer monolith. The monolith is a continuous material covalently bonded to the capillary or chip walls, with good flow-through properties. Epoxide ring-opening through amine attack by 5-amino-1,10-phenanthroline and coordination to dichloropalladium(ii) allows use of the microreactors for Suzuki–Miyaura catalysis. The long-term stability and reliability of the robust chip microreactor is demonstrated by operation for 96 h, exhibiting undiminished reactivity, and very low leaching of palladium.

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.

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.

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.

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.

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.

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

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.

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.

Lubricin (PRG4) reduces fouling susceptibility and improves sensitivity of carbon-based electrodes

Publisher: Elsevier BV

Date: 02-2020

DOI: 10.1016/J.ELECTACTA.2019.135574

Supported palladium catalysis using a heteroleptic 2-methylthiomethylpyridine-N,S-donor motif for Mizoroki-Heck and Suzuki-Miyaura coupling, including continuous organic monolith in capillary microscale flow-through mode

Publisher: Elsevier BV

Date: 09-2009

DOI: 10.1016/J.TET.2009.07.013

University Of Tasmania

Location: Australia

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Universiteit Leiden

Location: Netherlands

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Deakin University - Geelong Campus At Waurn Ponds

Location: Australia

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A High Speed, High Fidelity 3D Printer For Fabricating Microfluidic Devices

Start Date: 2016

End Date: 2019

Funder: Australian Research Council

Novel Approach To Study Mechanisms Of Na+ Transport In Plants Using Lab On A Chip Technology

Start Date: 2009

End Date: 2011

Funder: Australian Research Council

Fellowship For Experienced Researchers

Start Date: 2014

End Date: 2017

Funder: Alexander von Humboldt Foundation

Miniaturised Electrophoretic Systems For Distributed Environmental Sensing

Start Date: 2014

End Date: 2017

Funder: Australian Research Council

Disposable Microdevices For Fast Ion Analysis

Start Date: 2005

End Date: 2008

Funder: Australian Research Council

PFAS Monitoring Phase II

Start Date: 2020

End Date: 2020

Funder: Commonwealth Scientific and Industrial Research Organisation

Microreactors For Organic Synthesis

Start Date: 2006

End Date: 2008

Funder: Australian Research Council

Novel Approach To Study Mechanisms Of Na+ Transport In Plants Using Lab On A Chip Technology

Start Date: 2009

End Date: 2011

Funder: Australian Research Council

Multi-Purpose Mass Spectrometry Facility

Start Date: 2009

End Date: 2009

Funder: Australian Research Council

Integrated Functional Printing Facility For Advanced Material Technologies

Start Date: 2020

End Date: 2020

Funder: Australian Research Council

Disposable Microdevices For Fast Ion Analysis

Start Date: 2005

End Date: 2008

Funder: Australian Research Council

Hyphenated Capillary Electrophoresis-Mass Spectrometer Facility

Start Date: 2006

End Date: 2006

Funder: Australian Research Council

Microreactors For Organic Synthesis

Start Date: 2006

End Date: 2008

Funder: Australian Research Council

A High Speed, High Fidelity 3D Printer For Fabricating Microfluidic Devices

Start Date: 2017

End Date: 2020

Funder: Australian Research Council

Miniaturised Electrophoretic Systems For Distributed Environmental Sensing

Start Date: 2014

End Date: 2017

Funder: Australian Research Council

Hyphenated Capillary Electrophoresis - Mass Spectrometry Facility

Start Date: 2006

End Date: 2006

Funder: Australian Research Council

ARC Training Centre For Portable Analytical Separation Technologies

Start Date: 2014

End Date: 2016

Funder: Australian Research Council

Microfluidic Technology To Help Understand Physical Damage To Brain Cells

Start Date: 2015

End Date: 2017

Funder: Australian Research Council

Microfluidic Technology To Help Understand Physical Damage To Brain Cells

Start Date: 2015

End Date: 2017

Funder: Australian Research Council

ARC Training Centre For Portable Analytical Separation Technologies

Start Date: 2014

End Date: 2019

Funder: Australian Research Council

Driving Farming Productivity And Disease Prevention

Start Date: 2019

End Date: 2023

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0663416

Start Date: 03-2006

End Date: 12-2009

Amount: $280,000.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP220100252

Start Date: 2023

End Date: 12-2026

Amount: $799,084.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0987402

Start Date: 2009

End Date: 12-2013

Amount: $220,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0557803

Start Date: 01-2005

End Date: 07-2010

Amount: $250,000.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE200100168

Start Date: 06-2020

End Date: 09-2023

Amount: $550,000.00

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

Industrial Transformation Research Hubs - Grant ID: IH180100002

Start Date: 03-2019

End Date: 03-2024

Amount: $5,000,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP230100721

Start Date: 05-2023

End Date: 05-2026

Amount: $501,180.00

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

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE0989491

Start Date: 2009

End Date: 12-2009

Amount: $172,025.00

Funder: Australian Research Council