1
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Liu Y, Xia L, Dutta D. Reduction in sample injection bias using pressure gradients generated on chip. Electrophoresis 2021; 42:983-990. [PMID: 33569844 DOI: 10.1002/elps.202000299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 01/21/2021] [Accepted: 01/29/2021] [Indexed: 11/10/2022]
Abstract
Sample injection in microchip-based capillary zone electrophoresis (CZE) frequently rely on the use of electric fields which can introduce differences in the injected volume for the various analytes depending on their electrophoretic mobilities and molecular diffusivities. While such injection biases may be minimized by employing hydrodynamic flows during the injection process, this approach typically requires excellent dynamic control over the pressure gradients applied within a microfluidic network. The current article describes a microchip device that offers this needed control by generating pressure gradients on-chip via electrokinetic means to minimize the dead volume in the system. In order to realize the desired pressure-generation capability, an electric field was applied across two channel segments of different depths to produce a mismatch in the electroosmotic flow rate at their junction. The resulting pressure-driven flow was then utilized to introduce sample zones into a CZE channel with minimal injection bias. The reported injection strategy allowed the introduction of narrow sample plugs with spatial standard deviations down to about 45 μm. This injection technique was later integrated to a capillary zone electrophoresis process for analyzing amino acid samples yielding separation resolutions of about 4-6 for the analyte peaks in a 3 cm long analysis channel.
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Affiliation(s)
- Yukari Liu
- Department of Chemistry, University of Wyoming, Laramie, WY, 82071, USA
| | - Ling Xia
- Department of Chemistry, University of Wyoming, Laramie, WY, 82071, USA
| | - Debashis Dutta
- Department of Chemistry, University of Wyoming, Laramie, WY, 82071, USA
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2
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Buyuktuncel E. Microchip Electrophoresis and Bioanalytical Applications. CURR PHARM ANAL 2019. [DOI: 10.2174/1573412914666180831100533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Microanalytical systems have aroused great interest because they can analyze extremely
small sample volumes, improve the rate and throughput of chemical and biochemical analysis in a way
that reduces costs. Microchip Electrophoresis (ME) represents an effective separation technique to perform
quick analytical separations of complex samples. It offers high resolution and significant peak
capacity. ME is used in many areas, including biology, chemistry, engineering, and medicine. It is established
the same working principles as Capillary Electrophoresis (CE). It is possible to perform electrophoresis
in a more direct and convenient way in a microchip. Since the electric field is the driving
force of the electrodes, there is no need for high pressure as in chromatography. The amount of the voltage
that is applied in some electrophoresis modes, e.g. Micelle Electrokinetic Chromatography (MEKC)
and Capillary Zone Electrophoresis (CZE), mainly determines separation efficiency. Therefore, it is
possible to apply a higher electric field along a considerably shorter separation channel, hence it is possible
to carry out ME much quicker.
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Affiliation(s)
- Ebru Buyuktuncel
- Faculty of Pharmacy, Department of Analytical Chemistry, Inonu University, 44280, Malatya, Turkey
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3
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Cheng Y, Guo C, Zhao B, Yang L. Fast analysis of domoic acid using microchip electrophoresis with laser-induced fluorescence detection. J Sep Sci 2017; 40:1583-1588. [DOI: 10.1002/jssc.201600982] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 12/26/2017] [Accepted: 01/18/2017] [Indexed: 01/08/2023]
Affiliation(s)
- Yongqiang Cheng
- Shandong Provincial Key Laboratory of Ocean Environment Monitoring Technology; Shandong Academy of Sciences Institute of Oceanographic Instrumentation; Qing Dao China
| | - Cuilian Guo
- Shandong Provincial Key Laboratory of Ocean Environment Monitoring Technology; Shandong Academy of Sciences Institute of Oceanographic Instrumentation; Qing Dao China
| | - Bin Zhao
- Shandong Provincial Key Laboratory of Ocean Environment Monitoring Technology; Shandong Academy of Sciences Institute of Oceanographic Instrumentation; Qing Dao China
| | - Li Yang
- Shandong Provincial Key Laboratory of Ocean Environment Monitoring Technology; Shandong Academy of Sciences Institute of Oceanographic Instrumentation; Qing Dao China
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4
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Han JP, Sun J, Wang L, Liu P, Zhuang B, Zhao L, Liu Y, Li CX. The Optimization of Electrophoresis on a Glass Microfluidic Chip and its Application in Forensic Science. J Forensic Sci 2017; 62:1603-1612. [PMID: 28168694 DOI: 10.1111/1556-4029.13408] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Revised: 10/23/2016] [Accepted: 11/29/2016] [Indexed: 11/29/2022]
Abstract
Microfluidic chips offer significant speed, cost, and sensitivity advantages, but numerous parameters must be optimized to provide microchip electrophoresis detection. Experiments were conducted to study the factors, including sieving matrices (the concentration and type), surface modification, analysis temperature, and electric field strengths, which all impact the effectiveness of microchip electrophoresis detection of DNA samples. Our results showed that the best resolution for ssDNA was observed using 4.5% w/v (7 M urea) lab-fabricated LPA gel, dynamic wall coating of the microchannel, electrophoresis temperatures between 55 and 60°C, and electrical fields between 350 and 450 V/cm on the microchip-based capillary electrophoresis (μCE) system. One base-pair resolution could be achieved in the 19-cm-length microchannel. Furthermore, both 9947A standard genomic DNA and DNA extracted from blood spots were demonstrated to be successfully separated with well-resolved DNA peaks in 8 min. Therefore, the microchip electrophoresis system demonstrated good potential for rapid forensic DNA analysis.
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Affiliation(s)
- Jun P Han
- Key Laboratory of Forensic Genetics, Beijing Engineering Research Center of Crime Scene Evidence Examination, Institute of Forensic Science, Ministry of Public Security, Beijing, 100038, China.,Forensic Science and Technology Department of Chaoyang Sub-bureau, Beijing Public Security Bureau, Beijing, 100102, China
| | - Jing Sun
- Key Laboratory of Forensic Genetics, Beijing Engineering Research Center of Crime Scene Evidence Examination, Institute of Forensic Science, Ministry of Public Security, Beijing, 100038, China
| | - Le Wang
- Key Laboratory of Forensic Genetics, Beijing Engineering Research Center of Crime Scene Evidence Examination, Institute of Forensic Science, Ministry of Public Security, Beijing, 100038, China
| | - Peng Liu
- Tsinghua University, Beijing, 100084, China
| | - Bin Zhuang
- Tsinghua University, Beijing, 100084, China
| | - Lei Zhao
- Key Laboratory of Forensic Genetics, Beijing Engineering Research Center of Crime Scene Evidence Examination, Institute of Forensic Science, Ministry of Public Security, Beijing, 100038, China
| | - Yao Liu
- Key Laboratory of Forensic Genetics, Beijing Engineering Research Center of Crime Scene Evidence Examination, Institute of Forensic Science, Ministry of Public Security, Beijing, 100038, China
| | - Cai X Li
- Key Laboratory of Forensic Genetics, Beijing Engineering Research Center of Crime Scene Evidence Examination, Institute of Forensic Science, Ministry of Public Security, Beijing, 100038, China
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5
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Gabriel EF, dos Santos RA, Lobo-Júnior EO, Rezende KC, Coltro WK. Hydrodynamic injection on electrophoresis microchips using an electronic micropipette. Talanta 2017; 162:19-23. [DOI: 10.1016/j.talanta.2016.09.046] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Revised: 09/16/2016] [Accepted: 09/17/2016] [Indexed: 01/06/2023]
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6
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Ha JW, Hahn JH. Acupuncture injection for field amplified sample stacking and glass microchip-based capillary gel electrophoresis. Electrophoresis 2016; 38:521-524. [DOI: 10.1002/elps.201600469] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Revised: 11/04/2016] [Accepted: 11/05/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Ji Won Ha
- Department of Chemistry; University of Ulsan; Ulsan South Korea
| | - Jong Hoon Hahn
- Department of Chemistry, BioNanotechnology Center; Pohang University of Science and Technology; Pohang South Korea
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7
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Ha JW, Hahn JH. Acupuncture Sample Injection for Microchip Capillary Electrophoresis and Electrokinetic Chromatography. Anal Chem 2016; 88:4629-34. [DOI: 10.1021/acs.analchem.6b00789] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ji Won Ha
- Department of Chemistry, University of Ulsan, 93 Daehak-Ro, Nam-Gu, Ulsan, 44610, South Korea
| | - Jong Hoon Hahn
- Department of Chemistry,
BioNanotechnology Center, Pohang University of Science and Technology, 77 Cheongam-Ro, Nam-Gu, Pohang, 37673, South Korea
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8
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Gaudry AJ, Nai YH, Guijt RM, Breadmore MC. Polymeric Microchip for the Simultaneous Determination of Anions and Cations by Hydrodynamic Injection Using a Dual-Channel Sequential Injection Microchip Electrophoresis System. Anal Chem 2014; 86:3380-8. [DOI: 10.1021/ac403627g] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Adam J. Gaudry
- Australian Centre
for Research on Separation Science, School of Physical Sciences: Chemistry,
Faculty of Science Engineering and Technology, University of Tasmania, Private
Bag 75, Hobart, Tasmania, 7001, Australia
| | - Yi Heng Nai
- Australian Centre
for Research on Separation Science, School of Physical Sciences: Chemistry,
Faculty of Science Engineering and Technology, University of Tasmania, Private
Bag 75, Hobart, Tasmania, 7001, Australia
| | - Rosanne M. Guijt
- Australian Centre
for Research on Separation Science, Pharmacy School of Medicine, Faculty
of Health Science, University of Tasmania, Private Bag 26, Hobart, Tasmania, 7001, Australia
| | - Michael C. Breadmore
- Australian Centre
for Research on Separation Science, School of Physical Sciences: Chemistry,
Faculty of Science Engineering and Technology, University of Tasmania, Private
Bag 75, Hobart, Tasmania, 7001, Australia
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9
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Saito RM, Coltro WKT, de Jesus DP. Instrumentation design for hydrodynamic sample injection in microchip electrophoresis: a review. Electrophoresis 2012; 33:2614-23. [PMID: 22965705 DOI: 10.1002/elps.201200089] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Reproducible and representative sample injection in microchip electrophoresis has been a bottleneck for quantitative analytical applications. Electrokinetic sample injection is the most used because it is easy to perform. However, this injection method is usually affected by sample composition and the bias effect. On the other hand, these drawbacks are overcome by the hydrodynamic (HD) sample injection, although this injection mode requires HD flow control. This review gives an overview of the basic principles, the instrumentation designs, and the performance of HD sample injection systems for microchip electrophoresis.
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Affiliation(s)
- Renata M Saito
- Institute of Chemistry, State University of Campinas, Campinas, São Paulo, Brazil
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10
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Hurth C, Gu J, Aboud M, Estes MD, Nordquist AR, McCord B, Zenhausern F. Direct loading of polymer matrices in plastic microchips for rapid DNA analysis: a comparative study. Electrophoresis 2012; 33:2604-11. [PMID: 22899270 DOI: 10.1002/elps.201200148] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We report the design and performance validation of microfluidic separation technologies for human identification using a disposable plastic device suitable for integration into an automated rapid DNA analysis system. A fabrication process for a 15-cm long hot-embossed plastic microfluidic devices with a smooth semielliptical cross section out of cyclic olefin copolymer is presented. We propose a mixed polymer solution of 95% w/v hydroxyethylcellulose and 5% w/v polyvinylpyrrolidone for a final polymer concentration of 2.5 or 3.0% to be used as coating and sieving matrix for DNA separation. This formulation allows preparing the microchip without pretreatment in a single-loading step and provides high-resolution separation (≈1.2 bp for fragments <200 bp), which is superior to existing commercial matrices under the same conditions. The hot-embossed device performance is characterized and compared to injection-molded devices made out of cyclic olefin copolymer based on their respective injector geometry, channel shape, and surface charges. Each device design is assessed by fluorescence videomicroscopy to evaluate the formation of injection plugs, then by comparing electropherograms for the separation of a DNA size standard relevant to human identification.
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Affiliation(s)
- Cedric Hurth
- Center for Applied Nanobioscience and Medicine, The University of Arizona College of Medicine, Phoenix, AZ 85004, USA.
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11
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Simultaneous analysis of seven oligopeptides in microbial fuel cell by micro-fluidic chip with reflux injection mode. Talanta 2012; 100:338-43. [DOI: 10.1016/j.talanta.2012.07.079] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Revised: 07/26/2012] [Accepted: 07/30/2012] [Indexed: 01/25/2023]
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12
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Karlinsey JM. Sample introduction techniques for microchip electrophoresis: A review. Anal Chim Acta 2012; 725:1-13. [DOI: 10.1016/j.aca.2012.02.052] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Revised: 02/25/2012] [Accepted: 02/29/2012] [Indexed: 12/24/2022]
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13
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Gáspár A, Koczka P, Carmona H, Gomez F. Split injection: A simple introduction of subnanoliter sample volumes for chip electrophoresis. Microchem J 2011. [DOI: 10.1016/j.microc.2011.05.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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14
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Kovarik ML, Lai HH, Xiong JC, Allbritton NL. Sample transport and electrokinetic injection in a microchip device for chemical cytometry. Electrophoresis 2011; 32:3180-7. [PMID: 22012764 DOI: 10.1002/elps.201100234] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2011] [Revised: 06/26/2011] [Accepted: 08/15/2011] [Indexed: 11/10/2022]
Abstract
Sample transport and electrokinetic injection bias are well characterized in capillary electrophoresis and simple microchips, but a thorough understanding of sample transport on devices combining electroosmosis, electrophoresis, and pressure-driven flow is lacking. In this work, we evaluate the effects of electric fields from 0 to 300 V/cm, electrophoretic mobilities from 10(-4) to 10(-6) cm(2)/Vs, and pressure-driven fluid velocities from 50 to 250 μm/s on sample injection in a microfluidic chemical cytometry device. By studying a continuous sample stream, we find that increasing electric field strength and electrophoretic mobility result in improved injection and that COMSOL simulations accurately predict sample transport. The effects of pressure-driven fluid velocity on injection are complex, and relative concentration values lie on a surface defined by pressure-driven flow rates. For high-mobility analytes, this surface is flat, and sample injection is robust despite fluctuations in flow rate. For lower mobility analytes, the surface becomes steeper, and injection depends strongly on pressure-driven flow. These results indicate generally that device design must account for analyte characteristics and specifically that this device is suited to high-mobility analytes. We demonstrate that for a suitable pair of peptides fluctuations in injection volume are correlated; electrokinetic injection bias is minimized; and electrophoretic separation is achieved.
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Affiliation(s)
- Michelle L Kovarik
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, USA
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15
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Wu J, Ferrance JP, Landers JP, Weber SG. Integration of a precolumn fluorogenic reaction, separation, and detection of reduced glutathione. Anal Chem 2010; 82:7267-73. [PMID: 20698502 PMCID: PMC2932763 DOI: 10.1021/ac101182r] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Reduced glutathione (GSH) has been determined by fluorescence detection after derivatization together with a variety of separations. The reactions between GSH and fluorescent reagents usually are carried out during the sample pretreatment and require minutes to hours for complete reactions. For continuous monitoring of GSH, it would be very convenient to have an integrated microdevice that could perform online precolumn derivatization, separation, and detection. Heretofore, thiol-specific fluorogenic reagents require fairly long reaction times, preventing effective online precolumn derivatization. We demonstrate here that the fluorogenic, thiol-specific reagent, ThioGlo-1, reacts rapidly enough for efficient precolumn derivatization. The second order rate constant for the reaction of GSH and reagent (pH 7.5, room temperature) is 2.1 x 10(4) M(-1)s(-1). The microchip integrates this precolumn derivatization, continuous flow gated sampling, separation, and detection on a single device. We have validated this device for monitoring GSH concentration continuously by studying the kinetics of glutathione reductase (EC 1.8.1.7), an enzyme that catalyzes the reduction of oxidized glutathione (GSSG) to GSH in the presence of beta-NADPH (beta-nicotinamide adenine dinucleotide phosphate, reduced form) as a reducing cofactor. During the experiment, GSH being generated in the enzymatic reaction was labeled with ThioGlo-1 as it passed through a mixing channel on the microfluidic chip. Derivatization reaction products were introduced into the analysis channel every 10 s using flow gated injections of 0.1 s. Baseline separation of the internal standard, ThioGlo-1, and the fluorescently labeled GSH was successfully achieved within 4.5 s in a 9 mm separation channel. Relative standard deviations of the peak area, peak height, and full width at half-maximum (fwhm) for the internal standard were 2.5%, 2.0%, and 1.0%, respectively, with migration time reproducibility for the internal standard of less than 0.1% RSD in any experiment. The GSH concentration and mass detection limit were 4.2 nM and approximately 10(-18) mol, respectively. The Michaelis constants (K(m)) for GSSG and beta-NADPH were found to be 40 +/- 11 and 4.4 +/- 0.6 muM, respectively, comparable with those obtained from UV/vis spectrophotometric measurements. These results show that this system is capable of integrating derivatization, injection, separation, and detection for continuous GSH determinations.
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Affiliation(s)
- Juanfang Wu
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | - Jerome P. Ferrance
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904
| | - James P. Landers
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904
| | - Stephen G. Weber
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
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16
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Price AK, Culbertson CT. Generation of Nonbiased Hydrodynamic Injections on Microfluidic Devices Using Integrated Dielectric Elastomer Actuators. Anal Chem 2009; 81:8942-8. [DOI: 10.1021/ac9015837] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Alexander K. Price
- Department of Chemistry, Kansas State University, 213 CBC Building, Manhattan, Kansas 66506
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17
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A micro-electrophoresis system based on a short capillary with hydrostatic pressure assisted separation and injection. Mikrochim Acta 2009. [DOI: 10.1007/s00604-009-0160-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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18
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Sohn OJ, Kim CK, Rhee JI. Immobilization of glucose oxidase and lactate dehydrogenase onto magnetic nanoparticles for bioprocess monitoring system. BIOTECHNOL BIOPROC E 2009. [DOI: 10.1007/s12257-008-0096-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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19
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Shaikh FA, Ugaz VM. DNA focusing using microfabricated electrode arrays. Methods Mol Biol 2009; 544:69-79. [PMID: 19488694 DOI: 10.1007/978-1-59745-483-4_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Focusing methods are a key component in many miniaturized DNA analysis systems because they enable dilute samples to be concentrated to detectable levels while being simultaneously confined within a specified volume inside the microchannel. In this chapter, we describe a focusing method based on a device design incorporating arrays of addressable on-chip microfabricated electrodes that can locally increase the concentration of DNA in solution by electrophoretically sweeping it along the length of a microchannel. By applying a low voltage (approximately 1-2 V) between successive pairs of neighboring electrodes, the intrinsically negatively charged DNA fragments are induced to migrate toward and collect at each anode, thereby allowing the quantity of accumulated DNA to be precisely metered. We have characterized the kinetics of this process, and found the response to be robust over a range of different sample compositions and buffer environments.
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Affiliation(s)
- Faisal A Shaikh
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX 77843-3122, USA
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20
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Gong M, Nikcevic I, Wehmeyer KR, Limbach PA, Heineman WR. Protein-aptamer binding studies using microchip affinity capillary electrophoresis. Electrophoresis 2008; 29:1415-22. [PMID: 18324729 PMCID: PMC3529586 DOI: 10.1002/elps.200700777] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The use of traditional CE to detect weak binding complexes is problematic due to the fast-off rate resulting in the dissociation of the complex during the separation process. Additionally, proteins involved in binding interactions often nonspecifically stick to the bare-silica capillary walls, which further complicates the binding analysis. Microchip CE allows flexibly positioning the detector along the separation channel and conveniently adjusting the separation length. A short separation length plus a high electric field enables rapid separations thus reducing both the dissociation of the complex and the amount of protein loss due to nonspecific adsorption during the separation process. Thrombin and a selective thrombin-binding aptamer were used to demonstrate the capability of microchip CE for the study of relatively weak binding systems that have inherent limitations when using the migration shift method or other CE methods. The rapid separation of the thrombin-aptamer complex from the free aptamer was achieved in less than 10 s on a single-cross glass microchip with a relatively short detection length (1.0 cm) and a high electric field (670 V/cm). The dissociation constant was determined to be 43 nM, consistent with reported results. In addition, aptamer probes were used for the quantitation of standard thrombin samples by constructing a calibration curve, which showed good linearity over two orders of magnitude with an LOD for thrombin of 5 nM at a three-fold S/N.
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Affiliation(s)
- Maojun Gong
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH 45221-0172, USA
| | - Irena Nikcevic
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH 45221-0172, USA
| | - Kenneth R. Wehmeyer
- Procter and Gamble Pharmaceuticals, Health Care Research Center, 8700 Mason-Montgomery Rd, Mason, OH 45040, USA
| | - Patrick A. Limbach
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH 45221-0172, USA
| | - William R. Heineman
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH 45221-0172, USA
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21
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Wu D, Qin J, Lin B. Electrophoretic separations on microfluidic chips. J Chromatogr A 2008; 1184:542-59. [PMID: 18207148 PMCID: PMC7094303 DOI: 10.1016/j.chroma.2007.11.119] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2007] [Revised: 11/17/2007] [Accepted: 11/30/2007] [Indexed: 02/07/2023]
Abstract
This review presents a brief outline and novel developments of electrophoretic separation in microfluidic chips. Distinct characteristics of microchip electrophoresis (MCE) are discussed first, in which sample injection plug, joule heat, channel turn, surface adsorption and modification are introduced, and some successful strategies and recognized conclusions are also included. Important achievements of microfluidic electrophoresis separation in small molecules, DNA and protein are then summarized. This review is aimed at researchers, who are interested in MCE and want to adopt MCE as a functional unit in their integrated microsystems.
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Affiliation(s)
| | - Jianhua Qin
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Bingcheng Lin
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
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22
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Wang W, Zhou F, Zhao L, Zhang JR, Zhu JJ. Improved hydrostatic pressure sample injection by tilting the microchip towards the disposable miniaturized CE device. Electrophoresis 2008; 29:561-6. [DOI: 10.1002/elps.200700207] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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23
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18 Coupling CE and microchip-based devices with mass spectrometry. ACTA ACUST UNITED AC 2008. [DOI: 10.1016/s0149-6395(07)00018-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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24
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Blas M, Delaunay N, Rocca JL. Electrokinetic-based injection modes for separative microsystems. Electrophoresis 2008; 29:20-32. [DOI: 10.1002/elps.200700389] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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25
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Blas M, Delaunay N, Rocca JL. Comparative study of floating and dynamic injection modes in electrokinetic separative microsystems. Electrophoresis 2007; 28:4629-37. [DOI: 10.1002/elps.200700011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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26
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Gong M, Wehmeyer KR, Limbach PA, Heineman WR. Flow manipulation for sweeping with a cationic surfactant in microchip capillary electrophoresis. J Chromatogr A 2007; 1167:217-24. [PMID: 17826787 PMCID: PMC2716996 DOI: 10.1016/j.chroma.2007.08.042] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2007] [Revised: 08/13/2007] [Accepted: 08/16/2007] [Indexed: 11/28/2022]
Abstract
Flow manipulation in sweeping microchip capillary electrophoresis (CE) is complicated by the free liquid communication between channels at the intersection, especially when the electroosmotic flows are mismatched in the main channel. Sweeping in traditional CE with cationic micelles is an effective way to concentrate anionic analytes. However, it is a challenge to transfer this method onto microchip CE because the dynamic coating process on capillary walls by cationic surfactants is interrupted when the sample solution free of surfactants is introduced into the microchip channels. This situation presents a difficulty in the sample loading, injection and dispensing processes. By adding surfactant at a concentration around the critical micelle concentration and by properly designing the voltage configuration, the flows in a microchip were effectively manipulated and this sweeping method was successfully moved to microchip CE using tetradecyltrimethylammonium bromide (TTAB). The sweeping effect of cationic surfactant in the sample solution was discussed theoretically and studied experimentally in traditional CE. The flows in a microchip were monitored with fluorescence imaging, and the injection and sweeping processes were studied by locating the detection point along the separation channel. A detection enhancement of up to 500-fold was achieved for 5-carboxyfluorescein.
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Affiliation(s)
- Maojun Gong
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH 45221-0172, USA
| | - Kenneth R. Wehmeyer
- Procter and Gamble Pharmaceuticals, Health Care Research Center, 8700 Mason-Montgomery Rd, Mason, OH 45040, USA
| | - Patrick A. Limbach
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH 45221-0172, USA
| | - William R. Heineman
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH 45221-0172, USA
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27
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Kim YH, Yang I, Park SR. Well-Less Capillary Array Electrophoresis Chip Using Hydrophilic Sample Bridges. Anal Chem 2007; 79:9205-10. [DOI: 10.1021/ac071115p] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Young Ho Kim
- Health Metrology Group, Korea Research Institute of Standards and Science, Daejeon, Korea
| | - Inchul Yang
- Health Metrology Group, Korea Research Institute of Standards and Science, Daejeon, Korea
| | - Sang-Ryoul Park
- Health Metrology Group, Korea Research Institute of Standards and Science, Daejeon, Korea
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28
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Blas M, Delaunay N, Ferrigno R, Rocca JL. Numerical simulations of the second-order electrokinetic bias observed with the gated injection mode in chips. Electrophoresis 2007; 28:2961-70. [PMID: 17661314 DOI: 10.1002/elps.200600692] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
It is well known that sample introduction via electrokinetic mode leads to a bias in conventional CE, which is proportional to the difference of electrophoretic mobilities between species. In electrophoretic separation chips using the gated injection mode, flow distribution at the crossjunction, which is linked to the electric field strength distribution during the loading step, induces an additional contribution to species discrimination. This second-order bias has a similar effect on quantitation like usual electrokinetic bias: the higher the analyte's apparent mobility, the larger the amount injected into the separation channel. The present paper assesses by numerical simulations the influence of several parameters, namely the injected amount, the electric field distribution, and the analyte-apparent Peclet number on this second-order bias.
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Affiliation(s)
- Maximilien Blas
- Laboratoire des Sciences Analytiques, UMR 5180 CNRS - Université Lyon I, Villeurbanne cedex, France
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29
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Gong M, Wehmeyer KR, Stalcup AM, Limbach PA, Heineman WR. Study of injection bias in a simple hydrodynamic injection in microchip CE. Electrophoresis 2007; 28:1564-71. [PMID: 17447241 PMCID: PMC2442562 DOI: 10.1002/elps.200600616] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The electrokinetically pinched method is the most commonly used mode for sample injection in microchip capillary electrophoresis (microCE) due to its simplicity and well-defined sample volume. However, the limited injection volume and the electrophoretic bias of the pinched injection may limit its universal usage to specific applications. Several hydrodynamic injection methods in microCE have been reported; however, almost all claimed that their methods are bias-free without considering the dispensing bias. To investigate the dispensing bias, a simple hydrodynamic injection was developed in single-T and double-T glass microchips. The sample flow was produced by hydrostatic pressure generated by the liquid level difference between the sample reservoir and the other reservoirs. The reproducibility of peak area and peak area ratio was improved to a significant extent using large-surface reservoirs for the buffer reservoir and the sample waste reservoir to reduce the Laplace pressure effect. Without a voltage applied on the sample solution, the voltage-related sample bias was eliminated. The dispensing bias was analyzed theoretically and studied experimentally. It was demonstrated that the dispensing bias existed and could be reduced significantly by appropriately setting up the voltage configuration and by controlling the appropriate liquid level difference.
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Affiliation(s)
- Maojun Gong
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH 45221-0172, USA
| | - Kenneth R. Wehmeyer
- Procter and Gamble Pharmaceuticals, Health Care Research Center, 8700 Mason-Montgomery Rd, Mason, OH 45040, USA
| | - Apryll M. Stalcup
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH 45221-0172, USA
| | - Patrick A. Limbach
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH 45221-0172, USA
| | - William R. Heineman
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH 45221-0172, USA
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30
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Chen C, Hahn JH. Dual-Channel Method for Interference-Free In-Channel Amperometric Detection in Microchip Capillary Electrophoresis. Anal Chem 2007; 79:7182-6. [PMID: 17708674 DOI: 10.1021/ac070721h] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A novel in-channel amperometric detection method for microchip capillary electrophoresis (CE) has been developed to avoid the interference from applied potential used in the CE separation. Instead of a single separation channel as in conventional CE microchips, we use a dual-channel configuration consisting of two different parallel separation and reference channels. A working electrode (WE) and a reference electrode (RE) are placed equally at a distance 200 microm from its outlet on each channel. Running buffer flows through the reference channel. Our dual-channel CE microchips consist of a poly(dimethylsiloxane) (PDMS) upper plate and a glass lower plate to form a PDMS/glass hybrid chip. Amperometric signals are measured without any potential shift and interference from the applied CE potential, and CE separation maintains its high resolution because this in-channel configuration does not allow additional band broadening that is notorious in end-channel and off-channel configurations. The high performance of this new in-channel electrochemical detection methodology for CE has been demonstrated by analyzing a mixture of electrochemically active biomolecules: dopamine (DA), norepinephrine, and catechol. We have achieved a 0.1 pA detectability from the analysis of DA, which corresponds to a 1.8 nM concentration.
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Affiliation(s)
- Chuanpin Chen
- School of Environmental Science and Engineering and Department of Chemistry, BK School of Molecular Science, Pohang University of Science and Technology, San 31 Hyoja-Dong, Pohang 790-784, South Korea
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31
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Fu LM, Leong JC, Lin CF, Tai CH, Tsai CH. High performance microfluidic capillary electrophoresis devices. Biomed Microdevices 2007; 9:405-12. [PMID: 17487587 DOI: 10.1007/s10544-007-9049-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
This paper presents a novel microfluidic capillary electrophoresis (CE) device featuring a double-T-form injection system and an expansion chamber located at the inlet of the separation channel. This study addresses the principal material transport mechanisms depending on parameters such as the expansion ratio, the expansion length, the fluid flow. Its design utilizes a double-L injection technique and combines the expansion chamber to minimize the sample leakage effect and to deliver a high-quality sample plug into the separation channel so that the detection performance of the device is enhanced. Experimental and numerical testing of the proposed microfluidic device that integrates an expansion chamber located at the inlet of the separation channel confirms its ability to increase the separation efficiency by improving the sample plug shape and orientation. The novel microfluidic capillary electrophoresis device presented in this paper has demonstrated a sound potential for future use in high-quality, high-throughput chemical analysis applications and throughout the micro-total-analysis systems field.
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Affiliation(s)
- Lung-Ming Fu
- Department of Materials Engineering, National Pingtung University of Science and Technology, Pingtung, Taiwan 912
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32
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Tsai CH, Wang YN, Lin CF, Yang RJ, Fu LM. Experimental and numerical investigation into leakage effect in injectors of microfluidic devices. Electrophoresis 2007; 27:4991-8. [PMID: 17109377 DOI: 10.1002/elps.200500913] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This paper performs an experimental and numerical investigation into low-leakage injectors designed for electrophoresis microchips. The principal material transport mechanisms of electrokinetic migration, fluid flow, and diffusion are considered in developing a mathematical model of the electrophoresis process. Low-leakage injectors designed with injection channels orientated at various included angles are designed and tested. The numerical and experimental results indicate that the injector with a 30 degrees included angle successfully minimizes sample leakage and has an exciting potential for use in high-quality, high-throughput chemical analysis procedures and in many other applications in the field of micro-total analysis systems.
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Affiliation(s)
- Chien-Hsiung Tsai
- Department of Vehicle Engineering, National Pingtung University of Science and Technology, Pingtung, Taiwan
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33
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Zhang G, Du W, Liu BF, Hisamoto H, Terabe S. Characterization of electrokinetic gating valve in microfluidic channels. Anal Chim Acta 2007; 584:129-35. [PMID: 17386595 DOI: 10.1016/j.aca.2006.10.046] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2006] [Revised: 10/18/2006] [Accepted: 10/29/2006] [Indexed: 12/01/2022]
Abstract
Electrokinetic gating, functioning as a micro-valve, has been widely employed in microfluidic chips for sample injection and flow switch. Investigating its valving performance is fundamentally vital for microfluidics and microfluidics-based chemical analysis. In this paper, electrokinetic gating valve in microchannels was evaluated using optical imaging technique. Microflow profiles at channels junction were examined, revealing that molecular diffusion played a significant role in the valving disable; which could cause analyte leakage in sample injection. Due to diffusion, the analyte crossed the interface of the analyte flow and gating flow, and then formed a cometic tail-like diffusion area at channels junction. From theoretical calculation and some experimental evidences, the size of the area was related to the diffusion coefficient and the velocity of analytes. Additionally, molecular diffusion was also believed to be another reason of sampling bias in gated injection.
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Affiliation(s)
- Guiseng Zhang
- The Key Laboratory of Biomedical Photonics of MOE, Hubei Bioinformatics & Molecular Imaging Key Laboratory, Department of Systems Biology, College of Life Science & Technology, Huazhong University of Science and Technology, Wuhan 430074, China
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34
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Tsai CH, Hung MF, Chang CL, Chen LW, Fu LM. Optimal configuration of capillary electrophoresis microchip with expansion chamber in separation channel. J Chromatogr A 2006; 1121:120-8. [PMID: 16723132 DOI: 10.1016/j.chroma.2006.04.041] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2006] [Revised: 03/27/2006] [Accepted: 04/05/2006] [Indexed: 10/24/2022]
Abstract
This study develops a novel capillary electrophoresis (CE) microfluidic device featuring a conventional cross-form injection system and an expansion chamber located at the inlet of the separation channel. The combined injection system/expansion chamber arrangement is designed to deliver a high-quality sample band into the separation channel such that the detection performance of the device is enhanced. Numerical simulations are performed to investigate the electrokinetic transport processes in the microfluidic device and to establish the optimal configuration of the expansion chamber. The results indicate that an expansion chamber with an expansion ratio of 2.5 and an expansion length of 500 microm delivers a sample plug with the correct shape and orientation. With this particular configuration, the peak intensities of the sample are sharp and clearly distinguishable in the detection region of the separation channel. Therefore, this configuration is well suited for capillary electrophoresis applications which require a highly sensitive resolution of the sample plug. The novel CE microfluidic device developed in this study has an exciting potential for use in high-performance, high-throughput chemical analysis applications and in many other applications throughout the field of micro-total-analysis-systems.
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Affiliation(s)
- Chien-Hsiung Tsai
- Department of Vehicle Engineering, National Pingtung University of Science and Technology, Pingtung 912, Taiwan
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35
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Lacharme F, Gijs MAM. Single potential electrophoresis microchip with reduced bias using pressure pulse injection. Electrophoresis 2006; 27:2924-32. [PMID: 16639704 DOI: 10.1002/elps.200500723] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We propose two variants of a new injection technique for use in electrophoresis microchips, called "front gate pressure injection" and "back gate pressure injection", that both enable a controlled and reproducible sample introduction with reduced bias compared to electrokinetic gated injection. A continuous flow of a test solution of fluorescein/rhodamine B in 20 mM Tris/boric acid buffer (pH 8.6) sample test solution is electrokinetically driven near to the entrance of the separation channel, using a single voltage (3 kV) that is constant in time. A sample plug is injected in the separation channel by a pressure pulse of the order of 0.1 s. The latter is generated using the mechanical deflection of a PDMS membrane that is loosely placed on a dedicated chip reservoir. The analysis of the peak area ratio of the separated compounds demonstrates a nearly constant sample composition when using pressure-based injection. A small remaining injection bias for the shortest membrane deflection times can be attributed to a dilution effect of the charged compound due to the presence of an electrical field transverse to the sample flow boundary in the channel junction.
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Affiliation(s)
- Frédéric Lacharme
- Institute of Microelectronics and Microsystems, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
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36
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Shaikh FA, Ugaz VM. Collection, focusing, and metering of DNA in microchannels using addressable electrode arrays for portable low-power bioanalysis. Proc Natl Acad Sci U S A 2006; 103:4825-30. [PMID: 16551750 PMCID: PMC1458754 DOI: 10.1073/pnas.0506848103] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2005] [Indexed: 11/18/2022] Open
Abstract
Although advances in microfluidic technology have enabled increasingly sophisticated biosensing and bioassay operations to be performed at the microscale, many of these applications employ such small amounts of charged biomolecules (DNA, proteins, and peptides) that they must first be preconcentrated to a detectable level. Efficient strategies for precisely handling minute quantities of biomolecules in microchannel geometries are critically needed; however, it has proven challenging to achieve simultaneous concentration, focusing, and metering capabilities with current-generation sample-injection technology. By using microfluidic chips incorporating arrays of individually addressable microfabricated electrodes, we demonstrate that DNA can be sequentially concentrated, focused into a narrow zone, metered, and injected into an analysis channel. This technique transports charged biomolecules between active electrodes upon application of a small potential difference (1 V) and is capable of achieving orders of magnitude concentration increases within a small device footprint. The collected samples are highly focused, with sample zone size and shape defined solely by electrode geometry.
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Affiliation(s)
- Faisal A. Shaikh
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX 77843
| | - Victor M. Ugaz
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX 77843
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37
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Zhang L, Yin X, Fang Z. Negative pressure pinched sample injection for microchip-based electrophoresis. LAB ON A CHIP 2006; 6:258-64. [PMID: 16450036 DOI: 10.1039/b511924c] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
A simple method for injecting well-defined non-biased sample plugs into the separation channel of a microfluidic chip-based capillary electrophoresis system was developed by a combination of flows generated by negative pressure, electrokinetic and hydrostatic forces. This was achieved by using only a single syringe pump and a single voltage supply at constant voltage. In the loading step, a partial vacuum in the headspace of a sealed sample waste reservoir was produced using a syringe pump equipped with a 3-way valve. Almost instantaneously, sample was drawn from the sample reservoir across the injection intersection to the sample waste reservoir by negative pressure. Simultaneously, buffer flow from the remaining two buffer reservoirs pinched the sample flow to form a well-defined sample plug at the channel intersection. In the subsequent separation stage, the vacuum in headspace of the sample waste reservoir was released to terminate all flows generated by negative pressure, and the sample plug at the channel intersection was electrokinetically injected into the separation channel under the potential applied along the separation channel. The liquid levels of the four reservoirs were optimized to prevent sample leakage during the separation stage. The approach considerably simplified the operations and equipment for pinched injection in chip-based CE, and improved the throughput. Migration time precisions of 3.3 and 1.5% RSD for rhodamine123 (Rh123) and fluorescein sodium (Flu) in the separation of a mixture of Flu and Rh123 were obtained for 56 consecutive determinations with peak height precisions of 6.2% and 4.4% RSD for Rh123 and Flu, respectively.
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Affiliation(s)
- Lei Zhang
- Institute of Microanalytical Systems, Department of Chemistry, Zhejiang University, 310027, Hangzhou, China
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38
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Wenclawiak BW, Püschl RJ. Sample Injection for Capillary Electrophoresis on a Micro Fabricated Device/On Chip CE Injection. ANAL LETT 2006. [DOI: 10.1080/00032710500460932] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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39
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Karlinsey JM, Monahan J, Marchiarullo DJ, Ferrance JP, Landers JP. Pressure Injection on a Valved Microdevice for Electrophoretic Analysis of Submicroliter Samples. Anal Chem 2005; 77:3637-43. [PMID: 15924399 DOI: 10.1021/ac048115z] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A recent report describes a reversible valve that can be used in series to achieve diaphragm pumping on chip (Grover, W. H.; Skelley, A. M.; Liu, C. N.; Lagally, E. T.; and Mathies, R. A. Sens. Actuators, B 2003, 89, 315-323). Here, the functionality of an integrated diaphragm pump on a hybrid PDMS-glass microchip to perform pressure injections for electrophoretic separations is demonstrated. A chip design that can perform both pressure and electrokinetic (EK) injection is described, and a mixture of fluorescein and ROX dyes in borate buffer is utilized as a model sample system. Multiple electrophoretic separations of sample injected with pressure and voltage are compared. Over multiple EK injections, an electrophoretic bias is observed and the injected analytes are not representative of the sample, with the peak area ratio changing 20% after 20 runs. Over multiple pressure injections, however, the sample composition is maintained, with a 3.6% CV over 20 runs. The data presented show the ability to alternate between injection types and pressure-inject a representative sample volume after a bias has already been observed with multiple EK injections. Multiple pressure injections have been performed on sample volumes as low as 500 nL while maintaining sample composition, supporting its use in integrated systems for small-volume sampling.
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Affiliation(s)
- James M Karlinsey
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, USA
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40
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Vogt O, Pfister M, Marggraf U, Neyer A, Hergenroder R, Jacob P. A new two-chip concept for continuous measurements on PMMA-microchips. LAB ON A CHIP 2005; 5:205-211. [PMID: 15672136 DOI: 10.1039/b411739p] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A new concept for continuous measurements on microchips is presented. A PMMA (polymethylmethacrylate) based capillary electrophoresis chip with integrated conductivity detection is combined with a second chip, which undertakes the task of fluid handling and electrical connections. The combination of electrokinetic and hydrodynamic flows allows long-term continuous stable analyses with good reproducibilities of migration time and peak heights of analytes. The two-chip system is characterized in terms of stability and reproducibility of separation and detection of small ions. Relative standard deviations of <1% and 3% respectively for retention times and peak heights during long-term measurements can be achieved. The new system combines simple handling and automated analysis without the need for refilling, cleaning or removal of the separation chip after one or several measurements.
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Affiliation(s)
- Oliver Vogt
- Institute for Analytical Sciences, P.O. Box 101352, D-44013 Dortmund, Germany.
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41
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Cho SI, Lee SH, Chung DS, Kim YK. Bias-free pneumatic sample injection in microchip electrophoresis. J Chromatogr A 2005; 1063:253-6. [PMID: 15700479 DOI: 10.1016/j.chroma.2004.11.088] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We have developed a new microfluidic chip capable of accurate metering, pneumatic sample injection, and subsequent electrophoretic separation. The pneumatic injection scheme, enabling us to introduce a solution without sampling bias unlike electrokinetic injection, is based upon the hydrophobicity and wettability of channel surfaces. An accurately metered solution of 10 nL could be injected by pneumatic pressure into a hydrophilic separation channel through Y-shaped hydrophobic valves, which consist of polydimethylsiloxane (PDMS) and fluorocarbon (FC) film layers. We demonstrated the successful pneumatic injection of a red ink solution into the separation channel as a proof of the concept. A mixture of fluorescein and dichlorofluorescein (DCF) could be baseline-separated using a single power source in microchip electrophoresis.
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Affiliation(s)
- Seung Il Cho
- School of Electrical Engineering and Computer Science, Seoul National University, Seoul 151-744, Republic of Korea
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42
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Baldock SJ, Fielden PR, Goddard NJ, Kretschmer HR, Prest JE, Treves Brown BJ. Novel variable volume injector for performing sample introduction in a miniaturised isotachophoresis device. J Chromatogr A 2004; 1042:181-8. [PMID: 15296404 DOI: 10.1016/j.chroma.2004.05.062] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
A microdevice design furnished with a novel sample injector, capable of delivering variable volume samples, for miniaturised isotachophoretic separations is presented. Micromachining by direct milling was used to realise two flow channel network designs on poly(methyl methacrylate) chips. Both designs comprised a wide bore sample channel interfaced, via a short connection channel, to a narrow bore separation channel. Superior injection performance was observed with a connection channel angled at 45 degrees to the separation channel compared to a device using a channel angled at 90 degrees. Automated delivery of electrolytes to the microdevice was demonstrated with both hydrostatic pumping and syringe pumps; both gave reproducible sample injection. A range of different sampling strategies were investigated. Isotachophoretic separations of model analytes (metal ions and an anionic dye) demonstrated the potential of the device. Separations of ten metal cations were achieved in under 475 s.
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Affiliation(s)
- S J Baldock
- Department of Instrumentation and Analytical Science, UMIST, PO Box 88, Manchester M60 1QD, UK.
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43
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Cannon DM, Kuo TC, Bohn PW, Sweedler JV. Nanocapillary array interconnects for gated analyte injections and electrophoretic separations in multilayer microfluidic architectures. Anal Chem 2003; 75:2224-30. [PMID: 12918959 DOI: 10.1021/ac020629f] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An electrokinetic injection technique is described which uses a nuclear track-etched nanocapillary array to inject sample plugs from one layer of a microfluidic device into another vertically separated layer for electrophoretic separations. Gated injection protocols for analyte separations, reported here, establish nanocapillary array interconnects as a route to multilevel microfluidic analytical designs. The hybrid nanofluidic/microfluidic gated injection protocol allows sample preparation and separation to be implemented in separate horizontal planes, thereby achieving multilayer integration. Repeated injections and separations of FITC-labeled arginine and tryptophan, using 200-nm pore-diameter capillary array injectors in place of traditional cross injectors are used to demonstrate gated injection with a bias configuration that uses relay switching of a single high-voltage source. Injection times as rapid as 0.3 s along with separation reproducibilities as low as 1% for FITC-labeled arginine exemplify the capability for fast, serial separations and analyses. Impedance analysis of the micro-/nanofluidic network is used to gain further insight into the mechanism by which this actively controlled nanofluidic-interconnect injection method works. Gated sample introduction via a nanocapillary array interconnect allows the injection and separation protocols to be optimized independently, thus realizing the versatility needed for real-world implementation of rapid, serial microchip analyses.
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Affiliation(s)
- Donald M Cannon
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
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