Development of a Conductivity-Based Photothermal Absorbance Detector for Capillary Separations

Johnston, Stephen; Fadgen, Keith E.; Jorgenson, James W.

doi:10.1021/ac052223j

Cited by 15 publications

(19 citation statements)

References 23 publications

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“…A contactless, conductivity-based, absorbance detector for CE was developed (73). When analytes passed through the detector, they absorbed light from a 442-nm HeCd or 488-nm argon ion laser producing a thermal perturbation in the buffer, which changed the buffer conductivity.…”

Section: Detectionmentioning

confidence: 99%

Capillary Electrophoresis in Bioanalysis

2008

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Science reports ∼4800 hits on capillary electrophoresis (CE) including 410 reviews. Because of the prominence of CE techniques in bioanalysis, we decided make them the focus of this review and selected 200 hundred papers representing advances in this field. The selected papers cover advances in CE theory, instrumentation, and methodologies that are specific to various analytes of biological origin or relevance. The group of analytes includes nucleic acids, proteins and peptides, carbohydrates, lipids, single cells, and bioparticles. In addition, we have included advances in the use of CE to define functional assays or to investigate biomolecular interactions. The use of microfabricated devices for CE analysis was not included because this is already covered in other review. Technique Developments Separation SchemesDetermining the velocity of the electroosmotic flow (EOF) and how it changes during an electrophoretic separation is still an important research topic. A simple method for EOF measurements using so-called thermal marks was reported (1). Here, a tungsten filament caused punctual heating at the capillary wall and caused a perturbation in the electrolyte concentration. A sequence of these "thermal marks" then migrated with the EOF until each mark reached and was detected by a conductivity detector. The feasibility of using thermal marks as internal EOF standards in different separation systems was thereby demonstrated.Isoelectric focusing separates amphoteric analytes such as proteins or peptides by the differences in their isoelectric points. Most of the reports on capillary isoelectric focusing (cIEF) describe an initial focusing phase after which the focused zones are mobilized and detected. A dynamic cIEF method for protein analysis was reported (2). This technique made it possible to control each protein's position and focused width by moving the pH gradient within the capillary through manipulation of the electric fields. An important advantage of this approach is the capability of collecting focused analytes from the central section, suggesting that there may be great potential for introducing selectively focused proteins to a second separation dimension such as LC or CE.Micellar electrokinetic capillary chromatography (MEKC) is typically incompatible with electrospray mass spectrometry (ESI-MS) because the nonvolatile surfactants in the micellar phase result in complicated adduct formation and loss of sensitivity during the electrospray process and because the presence of the organic solvent needed for electrospray may cause instability in the micellar phase. These drawbacks were overcome by using synthetic polymeric surfactants that can work as a pseudostationary phase and provide stable electrospray (3). The polymeric surfactant was made by polymerizing three amino acidderived (L-leucinol, L-isoleucinol, L-valinol) sulfated chiral surfactants. These polymeric

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Section: Detectionmentioning

confidence: 99%

Capillary Electrophoresis in Bioanalysis

2008

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“…The separation of DNA fragments by CE -CCD could be enhanced with multiple-wall carbon nanotubes as buffer additive [91]. Recently, Johnston et al [92] developed a CCD-based absorbance detector for CE based on a photothermal process, which can be used to measure absorbance independently of optical path length. The CCD can also be combined with other detection technology.…”

Section: Conductivity Detectionmentioning

confidence: 99%

Capillary electrophoresis and microchip capillary electrophoresis with electrochemical and electrochemiluminescence detection

Wang²

2007

J of Separation Science

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Recent advances and key strategies in capillary electrophoresis and microchip CE with electrochemical detection (ECD) and electrochemiluminescence (ECL) detection are reviewed. This article consists of four main parts: CE-ECD; microchip CE-ECD; CE-ECL; and microchip CE-ECL. It is expected that ECD and ECL will become powerful tools for CE microchip systems and will lead to the creation of truly disposable devices. The focus is on papers published in the last two years (from 2005 to 2006).

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“…[31,32] Briefly, 6 mM DABSYL chloride in acetone and 1 mM glucosamine in water were dissolved in 50 mM carbonate buffer at pH 9.0 in a 1:1 ratio. This solution was then heated in a water bath at 75 °C for 12 minutes.…”

Section: Methodsmentioning

confidence: 99%

“…developed a photothermal absorbance detector using contactless conductivity with laser excitation as the light source for a capillary electrophoresis system. [31] In the course of characterizing the detector, they discovered that the sensitivity of the device was considerably lower than theoretically calculated. Simulations indicated the sensing region is much larger than the thermooptically heated volume due to the capacitive nature of contactless conductivity detection.…”

Section: Introductionmentioning

confidence: 99%

Development of a conductivity-based photothermal absorbance detection microchip using polyelectrolytic gel electrodes

Chun

Dennis

Welch

et al. 2017

Journal of Chromatography A

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The development and application of polyelectrolytic gel electrodes (PGEs) for a microfluidic photothermal absorbance detection system is described. The PGEs are used to measure changes in conductivity based on heat generation by analytes absorbing light and changing the solution viscosity. The PGEs are suitable for direct contact conductivity measurements since they do not degrade with exposure to high electric fields. Both a 2-electrode system with DC voltages and a 3-electrode system with AC voltages were investigated. Experimental factors including excitation voltage, excitation frequency, laser modulation frequency, laser power, and path length were tested. The limits of detection for the 3-electrode and 2-electrode systems are 500 nM and 0.55 nM for DABSYL-tagged glucosamine, respectively. In addition, an electrokinetic separation of a potassium, DABSYL-tagged glucosamine, Rhodamine 6G, and Rhodamine B mixture was demonstrated.

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Development of a Conductivity-Based Photothermal Absorbance Detector for Capillary Separations

Cited by 15 publications

References 23 publications

Capillary Electrophoresis in Bioanalysis

Capillary Electrophoresis in Bioanalysis

Capillary electrophoresis and microchip capillary electrophoresis with electrochemical and electrochemiluminescence detection

Development of a conductivity-based photothermal absorbance detection microchip using polyelectrolytic gel electrodes

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