Versatile method for electroosmotic flow measurements in microchip electrophoresis

Shakalisava, Yuliya; Poitevin, Martine; Viovy, Jean‐Louis; Descroix, Stéphanie

doi:10.1016/j.chroma.2008.12.029

Cited by 19 publications

(19 citation statements)

References 20 publications

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“…For fluorescein, we chose the effective mobility to result in the best fit with simulation and model predictions. The resulting value (−18.9 × 10 −9 m 2 V −1 s −1 ) is within the uncertainty bounds of values reported in the literature (Martin & Lindqvist 1975;Mchedlov-Petrossyan, Kukhtik & Alekseeva 1994;Shakalisava et al 2009) and accepted models for ionic strength correction (Bahga, Bercovici & Santiago 2010).…”

Section: Experimental Validationsupporting

confidence: 56%

Sample dispersion in isotachophoresis

Garcia-Schwarz¹,

Bercovici²,

Marshall³

et al. 2011

J. Fluid Mech.

115

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We present an analytical, numerical and experimental study of advective dispersion in isotachophoresis (ITP). We analyse the dynamics of the concentration field of a focused analyte in peak mode ITP. The analyte distribution is subject to electromigration, diffusion and advective dispersion. Advective dispersion results from strong internal pressure gradients caused by non-uniform electro-osmotic flow (EOF). Analyte dispersion strongly affects the sensitivity and resolution of ITP-based assays. We perform axisymmetric time-dependent numerical simulations of fluid flow, diffusion and electromigration. We find that analyte properties contribute greatly to dispersion in ITP. Analytes with mobility values near those of the trailing (TE) or leading electrolyte (LE) show greater penetration into the TE or LE, respectively. Local pressure gradients in the TE and LE then locally disperse these zones of analyte penetration. Based on these observations, we develop a one-dimensional analytical model of the focused sample zone. We treat the LE, TE and LE-TE interface regions separately and, in each, assume a local Taylor-Aris-type effective dispersion coefficient. We also performed well-controlled experiments in circular capillaries, which we use to validate our simulations and analytical model. Our model allows for fast and accurate prediction of the area-averaged sample distribution based on known parameters including species mobilities, EO mobility, applied current density and channel dimensions. This model elucidates the fundamental mechanisms underlying analyte advective dispersion in ITP and can be used to optimize detector placement in detection-based assays.

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Section: Experimental Validationsupporting

confidence: 56%

Sample dispersion in isotachophoresis

Garcia-Schwarz¹,

Bercovici²,

Marshall³

et al. 2011

J. Fluid Mech.

115

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“…Shakalisava et al [36] described that this method has been compared with classical current monitoring method in the same buffer. For high electroosmotic mobility value, the results obtained were similar whatever the method used.…”

Section: Characterization Of Chip Coatingsmentioning

confidence: 98%

“…A method that is based on apparent mobility measurement of a charged compound of known effective mobility by frontal electrophoresis has thus been developed [36]. Electroosmotic mobilities measurements have been performed at alkaline pH (20 mM borate buffer pH 9), where electroosmotic mobilities are expected to be high.…”

Section: Characterization Of Chip Coatingsmentioning

confidence: 99%

“…Several surface treatment methods including permanent coating with hydroxypropyl cellulose (HPC) or semipermanent coating with poly(dimethylacrylamide-co-allyl glycidyl ether) (PDMA-AGE) were characterized and compared for both chip materials. A novel frontal electrophoresis method, which has been developed by our group [36] and is especially interesting in case of very low EOF, was used to evaluate EOF suppression in the treated microchannels. The pH gradient formation was evaluated by separation of fluorescent pI markers with both chip materials and both surface treatments.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of microchip material and surface treatment options for IEF of allergenic milk proteins on microchips

et al. 2009

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The use of glass and PDMS microchips has been investigated to perform rapid and efficient separation of allergenic whey proteins by IEF. To decrease EOF and to limit protein adsorption, two coating procedures have been compared. The first one consists in immobilizing hydroxypropyl cellulose (HPC) and the second one poly(dimethylacrylamide-co-allyl glycidyl ether) (PDMA-AGE). EOF limitation has been evaluated using frontal electrophoresis of a fluorescent marker of known effective mobility. EOF velocity was decreased by a factor about 100 and 30, respectively. pH gradient formation has been evaluated for each microchip using fluorescent pI markers. It was demonstrated that as expected a coating was essential to avoid pH gradient drift. Both coatings were efficient on glass microchips, but only PDMA-AGE allowed satisfying focusing of pI markers on PDMS microchips. Fluorescent covalent and noncovalent labelings of milk proteins have been compared by IEF on slab-gels. IEF separation of three major allergenic whey proteins [beta-lactoglobulin A (pI 5.25) and B (pI 5.35) and alpha-lactalbumin (pI 4.2-4.5)] was performed in both microchips. Milk proteins were separated with better resolution and shorter analysis time than by classical CIEF. Finally, better resolutions for milk allergens separation were obtained on glass microchips.

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“…This method depends on the physicochemical properties of the species, such as high molar absorptivity, electroactivity, fluorescence, and so on. Alternative methods for the EOF monitoring employ photobleaching of molecules, 6-8 conductometry, 9 indirect amperometry, 10,11 indirect fluorescence, 12 frontal analysis, 13 and the creation of different temperature zones (thermal marks). 14,15 Because of its instrumental simplicity, the currentmonitoring method is also very popular.…”

Section: Introductionmentioning

confidence: 99%

Visible LED-Based Instrumentation for Photometric Determination of Electroosmotic Flow in Microchannels

Silva¹,

Deblire²,

Jesus³

et al. 2011

J. Braz. Chem. Soc.

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A instrumentação para a determinação fotométrica do fluxo eletrosmótico (EOF) em dispositivos microfluídicos é descrita neste trabalho. A instrumentação é baseada em componentes acessíveis e consiste em um microscópio trinocular e no fotodiodo integrado OPT101. Um diodo emissor de luz (LED) de alta intensidade foi utilizado como fonte de radiação. Para as determinações foram utilizadas soluções aquosas dos corantes azul patente V e azul de metileno. O sistema foi utilizado no monitoramento do EOF em microdispositivos de poli(dimetilsiloxano) (PDMS) e híbridos de toner/vidro. As mobilidades do EOF determinadas em pH 7,0 foram (5,75 ± 0,01)10 -4 cm 2 V -1 s -1 e (3,2 ± 0,1)10 -4 cm 2 V -1 s -1 para os dispositivos de toner/vidro e PDMS, respectivamente. Medidas reprodutíveis foram obtidas em todos os experimentos, levando a uma alta precisão na determinação. O método proposto foi comparado com o método tradicional de determinação do EOF que envolve a medida da corrente nos microcanais.An instrumental setup for electroosmotic flow (EOF) determination in microfluidic devices is described. The system is based on a trinocular microscope and an integrated photodiode OPT101. The radiation was provided by a high-intensity white LED. For the determinations, patent blue V and methylene blue aqueous solutions were used. The setup was applied for EOF monitoring in hybrid toner/glass and PDMS microchips. For the toner/glass device, the EOF mobility was determined to be (5.75 ± 0.01) 10 -4 cm 2 V -1 s -1 at pH 7.0. For PDMS devices the measured EOF mobility was (3.2 ± 0.1) 10 -4 cm 2 V -1 s -1 . Reproducible measurements were obtained in all experiments, which produced results with small errors. The proposed method was compared to the conventional current monitoring method.Keywords: electroosmotic flow, mTAS, Lab-on-a-chip, photometric methods, microfluidic devices IntroductionElectroosmotic flow (EOF) is the movement of solvent molecules caused by an applied voltage in a capillary system. EOF plays an essential role in electromigration separation techniques, such as capillary zone electrophoresis (CZE or free solution capillary electrophoresis, FSCE) or microchip electrophoresis, 1 since the velocity of the ions is influenced by the magnitude of the EOF. As an example, both positively and negatively charged species can be simultaneously analyzed due to the EOF. Moreover, the EOF magnitude could bring some information about the condition of the surface of the capillary or microchannel wall. In particular, the knowledge about the surface charge density (including not only the EOF magnitude but also the zeta potential) can be of paramount importance for preventing adsorption of analyte to the wall.It is well accepted that EOF has its origin on the unbalanced charge distribution in the region closer to the capillary/microchannel wall, the so called electrical double layer (EDL). More precisely, the flow is caused by the movement of excess ions in the diffuse portion of the EDL. Mathematical treatment of the EOF combines the Newto...

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Versatile method for electroosmotic flow measurements in microchip electrophoresis

Cited by 19 publications

References 20 publications

Sample dispersion in isotachophoresis

Sample dispersion in isotachophoresis

Evaluation of microchip material and surface treatment options for IEF of allergenic milk proteins on microchips

Visible LED-Based Instrumentation for Photometric Determination of Electroosmotic Flow in Microchannels

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