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De Moor T, Lagae L, Van Hoof C, Liu C, Van Roy W. Electric field gradient focusing with electro-osmotic flow to reduce analyte dispersion: Concept and numerical investigation. J Chromatogr A 2023; 1689:463726. [PMID: 36586281 DOI: 10.1016/j.chroma.2022.463726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 12/15/2022] [Accepted: 12/16/2022] [Indexed: 12/30/2022]
Abstract
In proteomics, the need to precisely examine the protein compounds of small samples, requires sensitive analytical methods which can separate and enrich compounds with high precision. Current techniques require a minimal analysis time to obtain satisfactory compound separation where longer analysis time means better separation of compounds. But, molecular diffusion will create broadening of the separated compound bands over time, increasing the peak width, and thus reducing the resolution and the enrichment. Electric field gradient focusing (EFGF) is a separation technique, in which proteins are simultaneously separated and enriched by balancing a gradient electrostatic force with a constant hydrodynamic drag force. Because of this balance, analytes are continuously pushed back to their focusing point, limiting the time-dependent peak broadening due to molecular diffusion. Current EFGF techniques are however still suffering from peak broadening because of flow-profile inhomogeneities. In this paper, we propose to use AC electro-osmotic flow (AC EOF) to create a homogeneous flow in EFGF. The interference between the electric field gradient and the AC EOF was thoroughly analysed and the concept was validated using numerical simulations. The results show that a plug flow is obtained on top of a small, distorted boundary layer. While applying different DC electric fields in the electrolyte, a constant flow velocity can be obtained by including a DC offset to the electrodes generating the AC EOF. The plug flow is then maintained over the whole separation channel length, while an electric field gradient is applied. This way, the flow-induced contribution to peak broadening can be minimized in EFGF devices. By modelling the separation of green fluorescent protein (GFP) and R-Phycoerythrin (R-PE), it was shown that the peak width of separated compounds can be reduced and that the separation resolution can be improved, compared to current EFGF methods.
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Affiliation(s)
- Tinne De Moor
- Department of Electrical Engineering, KU Leuven, Kasteelpark Arenberg 10 postbus 2440, 3001 Leuven, Belgium; IMEC, Kapeldreef 75, 3001 Leuven, Belgium.
| | - Liesbet Lagae
- IMEC, Kapeldreef 75, 3001 Leuven, Belgium; Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200d - bus 2412, 3001 Leuven, Belgium
| | - Chris Van Hoof
- Department of Electrical Engineering, KU Leuven, Kasteelpark Arenberg 10 postbus 2440, 3001 Leuven, Belgium; IMEC, Kapeldreef 75, 3001 Leuven, Belgium
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Trickett CA, Henderson RD, Guijt RM, Breadmore MC. Electric field gradient focusing using a variable width polyaniline electrode. Electrophoresis 2012; 33:3254-8. [DOI: 10.1002/elps.201200335] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2012] [Revised: 08/01/2012] [Accepted: 08/02/2012] [Indexed: 01/11/2023]
Affiliation(s)
- Christopher A. Trickett
- Australian Centre for Research on Separation Science, School of Chemistry; University of Tasmania; Hobart; Tasmania; Australia
| | - Rowan D. Henderson
- Australian Centre for Research on Separation Science, School of Chemistry; University of Tasmania; Hobart; Tasmania; Australia
| | - Rosanne M. Guijt
- School of Pharmacy; University of Tasmania; Hobart; Tasmania; Australia
| | - Michael C. Breadmore
- Australian Centre for Research on Separation Science, School of Chemistry; University of Tasmania; Hobart; Tasmania; Australia
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3
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Pan Y, Treacy S, Gu X, Miller D, Burczynski F. Evaluation and Optimization of Capillary Zone Electrophoresis for Common Drugs of Forensic Interest in Aqueous Matrix. CANADIAN SOCIETY OF FORENSIC SCIENCE JOURNAL 2012. [DOI: 10.1080/00085030.2012.10757190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Anand RK, Sheridan E, Knust KN, Crooks RM. Bipolar Electrode Focusing: Faradaic Ion Concentration Polarization. Anal Chem 2011; 83:2351-8. [DOI: 10.1021/ac103302j] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Robbyn K. Anand
- Department of Chemistry and Biochemistry, Center for Electrochemistry, and the Center for Nano- and Molecular Science and Technology, The University of Texas at Austin, 1 University Station, A5300, Austin, Texas 78712-0165, United States
| | - Eoin Sheridan
- Department of Chemistry and Biochemistry, Center for Electrochemistry, and the Center for Nano- and Molecular Science and Technology, The University of Texas at Austin, 1 University Station, A5300, Austin, Texas 78712-0165, United States
| | - Kyle N. Knust
- Department of Chemistry and Biochemistry, Center for Electrochemistry, and the Center for Nano- and Molecular Science and Technology, The University of Texas at Austin, 1 University Station, A5300, Austin, Texas 78712-0165, United States
| | - Richard M. Crooks
- Department of Chemistry and Biochemistry, Center for Electrochemistry, and the Center for Nano- and Molecular Science and Technology, The University of Texas at Austin, 1 University Station, A5300, Austin, Texas 78712-0165, United States
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5
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Anand RK, Sheridan E, Hlushkou D, Tallarek U, Crooks RM. Bipolar electrode focusing: tuning the electric field gradient. LAB ON A CHIP 2011; 11:518-27. [PMID: 21120239 DOI: 10.1039/c0lc00351d] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Bipolar electrode (BPE) focusing is a developing technique for enrichment and separation of charged analytes in a microfluidic channel. The technique employs a bipolar electrode that initiates faradaic processes that subsequently lead to formation of an ion depletion zone. The electric field gradient resulting from this depletion zone focuses ions on the basis of their individual electrophoretic mobilities. The nature of the gradient is of primary importance to the performance of the technique. Here, we report dynamic measurements of the electric field gradient showing that it is stable over time and that its axial position in the microchannel is directly correlated to the location of an enriched tracer band. The position of the gradient can be tuned with pressure-driven flow. We also show that a steeper electric field gradient decreases the breadth of the enriched tracer band and therefore enhances the enrichment process. The slope of the gradient can be tuned by altering the buffer concentration: higher concentrations result in a steeper gradient. Coating the channel with the neutral block co-polymer Pluronic also results in enhanced enrichment.
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Affiliation(s)
- Robbyn K Anand
- Department of Chemistry and Biochemistry, Center for Electrochemistry, University of Texas at Austin, 1 University Station, A5300, Austin, Texas 78712-0165, USA
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Affiliation(s)
- Nicholas W. Frost
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455
| | - Meng Jing
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455
| | - Michael T. Bowser
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455
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7
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Burke JM, Ivory CF. Influence of the semi-permeable membrane on the performance of dynamic field gradient focusing. Electrophoresis 2010; 31:893-901. [PMID: 20191552 DOI: 10.1002/elps.200900222] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
This paper is part of our continued effort to understand the underlying principles of dynamic field gradient focusing. In this investigation, we examined three problems associated with the use of a semi-permeable membrane. First, the influence of steric and ionic exclusion of current carrying ions through the membrane was examined. It was found that resistance to the transport of ions across the membrane resulted in a shallowing of the electric field profile and an increase in the size of the defocusing zone, which is where the slope of the electric field is reversed so that it disperses rather than concentrates solutes. These problems could be reduced by using a membrane with large pores relative to the size of the buffering ions and completely void of fixed charges. Next, a numerical simulation was used to investigate concentration polarization of protein onto the surface of the membrane. Due to the presence of a transverse electric field, species were pulled toward the membrane. If the membrane is restrictive to those species, a concentrated, polarized layer will form on the surface. The simulation showed that by decreasing the channel to a depth of 20 microm, the concentrated region next to the membrane could be reduced. Finally, it was found that changes in column volume due to loss of membrane structural integrity could be mitigated by including a porous ceramic support. The variation in peak elution times was decreased from greater than 20% to less than 3%.
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Affiliation(s)
- Jeffrey M Burke
- Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164-2710, USA
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Burke JM, Huang Z, Ivory CF. Simultaneous separation of negatively and positively charged species in dynamic field gradient focusing using a dual polarity electric field. Anal Chem 2009; 81:8236-43. [PMID: 19722517 DOI: 10.1021/ac901634y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Dynamic field gradient focusing (DFGF) utilizes an electric field gradient established by a computer-controlled electrode array to separate and concentrate charged analytes at unique axial positions. Traditionally, DFGF has been restricted to the analysis of negatively charged species due to limitations in the software of our voltage controller. This paper introduces a new voltage controller capable of operating under normal polarity (positive potentials applied to the electrode array) and reversed polarity (negative potentials applied to the electrode array) for the separation of negatively and positively charged analytes, respectively. The experiments conducted under normal polarity and reversed polarity illustrate the utility of the new controller to perform reproducible DFGF separations (elution times showing less than 1% run-to-run variation) over a wide pH range (3.08 to 8.5) regardless of the protein charge. A dual polarity experiment is then shown in which the separation channel has been divided into normal polarity and reversed polarity regions. This simultaneous separation of negatively charged R-phycoerythrin (R-PE) and positively charged cytochrome c (CYTC) within the same DFGF apparatus is shown.
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Affiliation(s)
- Jeffrey M Burke
- Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA, USA
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Meighan MM, Staton SJR, Hayes MA. Bioanalytical separations using electric field gradient techniques. Electrophoresis 2009; 30:852-65. [DOI: 10.1002/elps.200800614] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Breadmore MC, Thabano JRE, Dawod M, Kazarian AA, Quirino JP, Guijt RM. Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2006-2008). Electrophoresis 2009; 30:230-48. [DOI: 10.1002/elps.200800435] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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