On-Column Sample Concentration Using Field Amplification in CZE

Chien, Ring‐Ling; Burgi, Dean S.

doi:10.1021/ac00032a721

Cited by 348 publications

(201 citation statements)

References 10 publications

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“…Preconcentration in FASS is achieved by generating a high electrical field within an injected sample plug, that rapidly drives and stacks sample ions at the ends of that plug [52][53][54][55]. This field amplification is created when the sample is dissolved in a buffer that has a much lower conductivity than the surrounding running buffer used for separation.…”

Section: Field-amplified Sample Stackingmentioning

confidence: 99%

A microchip electrophoresis system with integrated in-plane electrodes for contactless conductivity detection

2002

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We present a new approach for contactless conductivity detection for microchip-based capillary electrophoresis (CE). The detector integrates easily with well-known microfabrication techniques for glass-based microfluidic devices. Platinum electrodes are structured in recesses in-plane with the microchannel network after glass etching, which allows precise positioning and batch fabrication of the electrodes. A thin glass wall of 10-15 microm separates the electrodes and the buffer electrolyte in the separation channel to achieve the electrical insulation necessary for contactless operation. The effective separation length is 34 mm, with a channel width of 50 microm and depth of 12 microm. Microchip CE devices with conductivity detection were characterized in terms of sensitivity and linearity of response, and were tested using samples containing up to three small cations. The limit of detection for K+ (18 microM) is good, though an order of magnitude higher than for comparable capillary-based systems and one recently reported example of contactless conductivity on chip. However, an integrated field-amplified stacking step could be employed prior to CE to preconcentrate the sample ions by a factor of four.

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Section: Field-amplified Sample Stackingmentioning

confidence: 99%

A microchip electrophoresis system with integrated in-plane electrodes for contactless conductivity detection

2002

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“…The difference between the local electroosmotic velocities in different regions will generate a back laminar flow, which results in extra peak broadening. This model was also used by many groups in the studies of EOF control using external radial voltage and in the peak broadening of sample stacking [18][19][20][21]. Towns and Regnier [22] have described how partial coverage of the capillary wall by adsorption of a protein leads to the mismatch between local and bulk electroosmotic velocity and consequently to a decrease in resolution.…”

Section: General Aspectsmentioning

confidence: 99%

Electroosmotic pumping in microchips with nonhomogeneous distribution of electrolytes

Chien

Bousse²

2002

Electrophoresis

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A general equation to calculate the node pressure at a junction in a microfluidic network is presented. The node pressure is generated from both the hydrodynamic flow due to the external applied hydraulic pressures and the electrokinetic flow resulted from the applied electric field. Pure electroosmotic flow has a plug-flow profile and pressure flow has a parabolic flow profile. In a first order approximation, these two flows can be treated separately, and the total flow is the sum of the two. An externally applied pressure simply creates a constant offset in the node pressure as long as the flow resistances remain the same. In a nonhomogeneous microfluidic network, where the electrical resistivity or the electroosmotic mobility is not constant everywhere, the differences in electroosmotic flow in various sections of the network will create an electroosmotically induced pressure at the internal nodes. Our theoretical approach can easily be extended to networks with more than one internal node. One prediction of this theory is that any variation in electroosmotic mobility or solution resistivity in different network branches will generate a pressure, and can thus be used as a pump. As an example, we demonstrate electroosmotic pumping in a high-low buffer system.

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“…It may take place when the sample compounds encounter isotachophoretic concentration at the interface between sample zone and buffer (isotachophoretic sample stacking, ITPSS) [15] or when the conductivity of the sample is smaller than that of the buffer (field-amplified sample stacking, FASS) [16]. Recently, large-volume sample stacking (LVSS) without polarity switching was demonstrated to improve detection limits of charged analytes by more than 100-fold.…”

Section: Introductionmentioning

confidence: 99%

Large-volume sample stacking for analysis of ethylenediaminetetraacetic acid by capillary electrophoresis

et al. 2002

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A simple, quick, and sensitive capillary electrophoretic technique-large volume stacking using the electroosmotic flow (EOF) pump (LVSEP) - has been developed for determining ethylenediaminetetraacetic acid (EDTA) in drinking water for the first time. It is based on a precapillary complexation of EDTA with Fe(III) ions, followed by large-volume sample stacking and direct UV detection at 258 nm. The curve of peak response versus concentration was linear from 5.0 to 600.0 microg/L, and 0.7 to 30.0 mg/L. The regression coefficients were 0.9988 and 0.9990, respectively. The detection limit of the current technique for EDTA analysis was 0.2 microg/L with an additional 10-fold preconcentration procedure, based on the signal-to-noise ratio of 3. As opposed to the classical capillary zone electrophoresis (CE) method, the detection limit was improved about 1000-fold by using this LVSEP method. To the best of our knowledge, it represents the highest sensitivity for EDTA analysis via CE. Several drinking water samples were tested by this novel method with satisfactory results.

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On-Column Sample Concentration Using Field Amplification in CZE

Cited by 348 publications

References 10 publications

A microchip electrophoresis system with integrated in-plane electrodes for contactless conductivity detection

A microchip electrophoresis system with integrated in-plane electrodes for contactless conductivity detection

Electroosmotic pumping in microchips with nonhomogeneous distribution of electrolytes

Large-volume sample stacking for analysis of ethylenediaminetetraacetic acid by capillary electrophoresis

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