Continuous Sample Pretreatment Using a Free-Flow Electrophoresis Device Integrated onto a Silicon Chip

Raymond, Daniel E.; Manz, A.; Widmer, Hans

doi:10.1021/ac00090a011

Cited by 272 publications

(297 citation statements)

References 20 publications

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“…(1) (2) Subdomains, i.e., channels of differing depths, were spatially defined as solids and numerically expressed as diffusion coefficients using the ratio of linear velocities determined by theory. 1 Boundary conditions defined outlets (P = 0), inlets (P = 1), and channel walls (insulation/ symmetry) of the μ-FFE designs numerically.…”

Section: Fluid Modeling and Channel Designmentioning

confidence: 99%

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Fast Electrophoretic Separation Optimization Using Gradient Micro Free-Flow Electrophoresis

Fonslow

Bowser

2008

Anal. Chem.

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The continuous nature of micro free-flow electrophoresis (μ-FFE) was used to monitor the effect of a gradient of buffer conditions on the separation. This unique application has great potential for fast optimization of separation conditions and estimation of equilibrium constants. COMSOL was used to model pressure profiles in the development of a new μ-FFE design that allowed even application of a buffer gradient across the separation channel. The new design was fabricated in an all glass device using our previously published multiple-depth etch method (Fonslow, B. R.; Barocas, V. H.; Bowser, M. T. Anal. Chem. 2006, 78, 5369-5374, ref 1 ). Fluorescein solutions were used to characterize the applied gradients in the separation channel. Linear gradients were observed when buffer conditions were varied over a period of 5-10 min. The effect of a gradient of 0-50 mM hydroxypropyl-β-cyclodextrin (HP-β-CD) on the separation of a group of 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) labeled primary amines was monitored as a proof of concept experiment. Direct comparisons to capillary electrophoresis (CE) separations performed under the same conditions were made. Gradient μ-FFE recorded 60 separations during a 5 min gradient allowing nearly complete coverage across a range of HP-β-CD concentrations. In comparison, 4 h were required to assess 15 sets of conditions across the same range of HP-β-CD concentrations using CE. Qualitatively, μ-FFE separations were predictive of the migration order and spacing of peaks in CE electropherograms measured under the same conditions. Data were fit to equations describing 1:1 analyte-additive binding to allow a more quantitative comparison between gradient μ-FFE and CE.Micro free-flow electrophoresis (μ-FFE) is an analytical separation technique used to separate a continuously flowing stream of charged analytes. 2,3 A thin sample stream is introduced into a planar separation channel with buffer running in parallel. An electric field is applied perpendicularly across the separation channel, and charged analytes are deflected laterally based on their electrophoretic mobility. Thus far, μ-FFE separations have been limited to simple separations of fluorescent dyes, 4-6 fluorescently labeled amino acids, 2 and fluorescently labeled proteins. 3,7 μ-FFE's larger-scale, preparative counterpart has proven useful in separating a range of analytes, including cells, 8,9 cellular components, 10-14 and proteins. [15][16][17] In the near future, μ-FFE could be useful in analysis or micropreparative separations of the same analytes.Recently several researchers have investigated a variety of fabrication methods for μ-FFE devices to improve their performance. [4][5][6][18][19][20] In early designs two major problems were encountered. Inefficient removal of electrolysis products, manifested as bubbles, from the electrode channels degraded separations. 4 Also, channel designs used to minimize the effects of the bubbles reduced the electric field applied in the separation channel. 5,6 These probl...

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Section: Fluid Modeling and Channel Designmentioning

confidence: 99%

“…2,3 A thin sample stream is introduced into a planar separation channel with buffer running in parallel. An electric field is applied perpendicularly across the separation channel, and charged analytes are deflected laterally based on their electrophoretic mobility.…”

Section: Introductionmentioning

confidence: 99%

Fast Electrophoretic Separation Optimization Using Gradient Micro Free-Flow Electrophoresis

Fonslow

Bowser

2008

Anal. Chem.

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“…In the past years, many kinds of material have been used as raw material for fabricating microfluidic devices, such as silicone [1], glass [2], quartz and polymers [3][4][5]. Among these materials, polymers have been focused on greatly because of universal raw materials, low cost, accessible to large-scale manufacture and other especial peculiarities.…”

Section: Introductionmentioning

confidence: 99%

Development of a gel monolithic column polydimethylsiloxane microfluidic device for rapid electrophoresis separation

Zeng

Wang

et al. 2006

Talanta

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“…1,2 Most published reports utilizing microchips to separate and detect analysis of interest have concentrated on using electrokinetically driven separation schemes. [3][4][5][6][7] Investigations from a different standpoint have been few in number. 8,9 However, microchips offer advantages concerning the scale merits of microspace, such as a short diffusion distance and the high interface-to-volume ratio, the specific interface area; we thus considered that they are an ideal tool to study molecular transport between two different phases, i.e., solvent extraction.…”

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confidence: 99%

Molecular Transport between Two Phases in a Microchannel

et al. 2000

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Today, microfabricated devices (microchips) have attracted considerable attention because of their vast applicability and versatility. 1,2 Most published reports utilizing microchips to separate and detect analysis of interest have concentrated on using electrokinetically driven separation schemes. [3][4][5][6][7] Investigations from a different standpoint have been few in number. 8,9 However, microchips offer advantages concerning the scale merits of microspace, such as a short diffusion distance and the high interface-to-volume ratio, the specific interface area; we thus considered that they are an ideal tool to study molecular transport between two different phases, i.e., solvent extraction.In the present paper, we report on the first demonstration using a microchip to study molecular transport between two phases. ExperimentalWe have described the experimental apparatus and the principle of measurement for the thermal lens microscope (TLM) in detail previously. [10][11][12] The excitation beam was an Ar + laser of 488.0 nm which was mechanically chopped by a light chopper at 1.69 kHz. The probe beam was a He-Ne laser of 632.8 nm. Two laser beams were introduced coaxially into an optical microscope and tightly focused into a sample in a microchannel (100 µm×150 µm cross section) by an 20×0.65 NA objective lens. The excitation beam passing through the sample was separated from the probe beam by an optical narrow band-pass filter and a diffraction grating. The intensity of the transmitted probe beam after passing through a pinhole was detected by a photodiode. The photodiode current, amplified by a low-noise preamplifier (×100), was fed into a lock-in amplifier.The fabrication method for our glass chip was also previously published.11,12 Figure 1 shows the layout and dimensions of the glass chip.Nickel(II) chloride, dimethylglyoxime, ethanol, sodium acetate, acetic acid, hydrochloric acid, and chloroform were obtained from Wako Pure Chemical Industries, Ltd. and were used as received. Chloroform was of analytical grade. The other chemicals were of guaranteed grade, and the water used was from a Millipore Milli-Q system. A 2.5 mM nickel(II) stock solution was prepared by dissolving nickel(II) chloride in a small amount of hydrochloric acid and diluting with water. Aqueous solutions of Ni(II) were prepared at concentrations of 2.5 -50 µM by successive dilution with water. A stock solution of dimethylglyoxime was prepared by dissolving dimethylglyoxime in a small amount of ethanol and diluting to 1 mM with water. An aqueous buffer solution was prepared as follows. Acetic acid (2.4 ml) and 12.25 mg of sodium acetate were mixed and diluted to 250 ml with water. The Ni-complex sample solutions were prepared with a 1:1:1 mixing volume ratio of the nickel(II) solution, buffer solution and dimethylglyoxime solution. Results and DiscussionA Ni-dimethylglyoxime complex solution and chloroform in each reservoir were introduced into the solvent-extraction region by suction, as shown in Fig. 1. The two solutions did not mix w...

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Continuous Sample Pretreatment Using a Free-Flow Electrophoresis Device Integrated onto a Silicon Chip

Cited by 272 publications

References 20 publications

Fast Electrophoretic Separation Optimization Using Gradient Micro Free-Flow Electrophoresis

Fast Electrophoretic Separation Optimization Using Gradient Micro Free-Flow Electrophoresis

Development of a gel monolithic column polydimethylsiloxane microfluidic device for rapid electrophoresis separation

Molecular Transport between Two Phases in a Microchannel

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