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Pukleš I, Páger C, Sakač N, Matasović B, Kovač-Andrić E, Šarkanj B, Samardžić M, Budetić M, Molnárová K, Marković D, Vesinger A, Jozanović M. A new green approach to L-histidine and β-alanine analysis in dietary supplements using rapid and simple contactless conductivity detection integrated with high-resolution glass-microchip electrophoresis. Anal Bioanal Chem 2024; 416:3605-3617. [PMID: 38713223 DOI: 10.1007/s00216-024-05314-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Revised: 03/28/2024] [Accepted: 04/19/2024] [Indexed: 05/08/2024]
Abstract
The analysis of dietary supplements is far less regulated than pharmaceuticals, leading to potential quality issues. Considering their positive effect, many athletes consume supplements containing L-histidine and β-alanine. A new microfluidic method for the determination of L-histidine and β-alanine in dietary supplement formulations has been developed. For the first time, capacitively coupled contactless conductivity detection was employed for the microchip electrophoresis of amino acids in real samples. A linear relationship between detector response and concentration was observed in the range of 10-100 µmol L-1 for L-histidine (R2 = 0.9968) and β-alanine (R2 = 0.9954), while achieved limits of detection (3 × S/N ratio) were 4.2 µmol L-1 and 5.2 µmol L-1, respectively. The accuracy of the method was confirmed using recovery experiments as well as CE-UV-VIS and HPLC-UV-VIS techniques. The developed method allows unambiguous identification of amino acids in native form without chemical derivatization and with the possibility of simultaneous analysis of amino acids with metal cations.
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Affiliation(s)
- Iva Pukleš
- Department of Chemistry, Josip Juraj Strossmayer University of Osijek, Cara Hadrijana 8, HR-31000, Osijek, Croatia
- Doctoral School of Chemistry, University of Pécs, Ifjúság útja, Pécs, 7624, Hungary
- Department of Analytical and Environmental Chemistry, Faculty of Sciences, University of Pécs, Ifjúság útja, Pécs, 7624, Hungary
| | - Csilla Páger
- Institute of Bioanalysis, Medical School, Szentágothai Research Center, University of Pécs, Pécs, Hungary
| | - Nikola Sakač
- Faculty of Geotechnical Engineering, University of Zagreb, Hallerova 7, HR-42000, Varaždin, Croatia
| | - Brunislav Matasović
- Department of Chemistry, Josip Juraj Strossmayer University of Osijek, Cara Hadrijana 8, HR-31000, Osijek, Croatia
| | - Elvira Kovač-Andrić
- Department of Chemistry, Josip Juraj Strossmayer University of Osijek, Cara Hadrijana 8, HR-31000, Osijek, Croatia
| | - Bojan Šarkanj
- Department of Food Technology, University North, Trg dr. Žarka Dolinara 1, HR-48000, Koprivnica, Croatia
| | - Mirela Samardžić
- Department of Chemistry, Josip Juraj Strossmayer University of Osijek, Cara Hadrijana 8, HR-31000, Osijek, Croatia
| | - Mateja Budetić
- Department of Chemistry, Josip Juraj Strossmayer University of Osijek, Cara Hadrijana 8, HR-31000, Osijek, Croatia
| | - Katarína Molnárová
- Department of Analytical Chemistry, Faculty of Science, Charles University, Hlavova 8, 12843, Prague 2, Czech Republic
| | - Dean Marković
- Department of Biotechnology, University of Rijeka, Radmile Matejčić 2, HR-51000, Rijeka, Croatia
| | - Ana Vesinger
- Pirelli Deutschland GmbH, Höchster Straße 48-60, 64747, Breuberg, Germany
| | - Marija Jozanović
- Department of Chemistry, Josip Juraj Strossmayer University of Osijek, Cara Hadrijana 8, HR-31000, Osijek, Croatia.
- Doctoral School of Chemistry, University of Pécs, Ifjúság útja, Pécs, 7624, Hungary.
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2
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Nasir Ahamed NN, Mendiola-Escobedo CA, Perez-Gonzalez VH, Lapizco-Encinas BH. Development of a DC-Biased AC-Stimulated Microfluidic Device for the Electrokinetic Separation of Bacterial and Yeast Cells. BIOSENSORS 2024; 14:237. [PMID: 38785711 PMCID: PMC11117482 DOI: 10.3390/bios14050237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2024] [Revised: 04/19/2024] [Accepted: 05/04/2024] [Indexed: 05/25/2024]
Abstract
Electrokinetic (EK) microsystems, which are capable of performing separations without the need for labeling analytes, are a rapidly growing area in microfluidics. The present work demonstrated three distinct binary microbial separations, computationally modeled and experimentally performed, in an insulator-based EK (iEK) system stimulated by DC-biased AC potentials. The separations had an increasing order of difficulty. First, a separation between cells of two distinct domains (Escherichia coli and Saccharomyces cerevisiae) was demonstrated. The second separation was for cells from the same domain but different species (Bacillus subtilis and Bacillus cereus). The last separation included cells from two closely related microbial strains of the same domain and the same species (two distinct S. cerevisiae strains). For each separation, a novel computational model, employing a continuous spatial and temporal function for predicting the particle velocity, was used to predict the retention time (tR,p) of each cell type, which aided the experimentation. All three cases resulted in separation resolution values Rs>1.5, indicating complete separation between the two cell species, with good reproducibility between the experimental repetitions (deviations < 6%) and good agreement (deviations < 18%) between the predicted tR,p and experimental (tR,e) retention time values. This study demonstrated the potential of DC-biased AC iEK systems for performing challenging microbial separations.
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Affiliation(s)
- Nuzhet Nihaar Nasir Ahamed
- Microscale Bioseparations Laboratory, Biomedical Engineering Department, Rochester Institute of Technology, 160 Lomb Memorial Drive, Rochester, NY 14623, USA; (N.N.N.A.); (C.A.M.-E.)
| | - Carlos A. Mendiola-Escobedo
- Microscale Bioseparations Laboratory, Biomedical Engineering Department, Rochester Institute of Technology, 160 Lomb Memorial Drive, Rochester, NY 14623, USA; (N.N.N.A.); (C.A.M.-E.)
- School of Engineering and Sciences, Tecnologico de Monterrey, Monterrey 64700, Nuevo Leon, Mexico
| | - Victor H. Perez-Gonzalez
- School of Engineering and Sciences, Tecnologico de Monterrey, Monterrey 64700, Nuevo Leon, Mexico
| | - Blanca H. Lapizco-Encinas
- Microscale Bioseparations Laboratory, Biomedical Engineering Department, Rochester Institute of Technology, 160 Lomb Memorial Drive, Rochester, NY 14623, USA; (N.N.N.A.); (C.A.M.-E.)
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3
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da Costa ET, do Lago CL. Improving hydrodynamic injection in capillary electrophoresis by using the integral of pressure. Electrophoresis 2024; 45:609-617. [PMID: 38037281 DOI: 10.1002/elps.202300242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 11/14/2023] [Accepted: 11/20/2023] [Indexed: 12/02/2023]
Abstract
A careful analysis of the typical devices and conditions used during hydrodynamic injection in capillary electrophoresis shows that the Hagen-Poiseuille model for the laminar flow is valid, even during the transitions of pressure. Therefore, the monitoring of pressure becomes a reliable approach to evaluate the effective injected volume, because the volume is proportional to the integral of pressure (IoP) over time. A piezoresistive sensor was used to monitor the air pressure at headspace of the sample vial. A set of 18 injections at 50 mbar and different times were used to evaluate the use of the normalization of the peak areas of the analytes by the IoP to compensate for imperfection during the injection. There was a significant decrease in relative standard deviation (RSD), and the proposed approach presented results similar to the use of internal standard. In addition, a microcontroller was used not only to monitor the pressure but also to command a peristaltic pump and a solenoid valve creating a system that dynamically controls the applied pressure and stops the injection when the desired value of IoP is reached. The system was used in a proof of concept in which different combinations of pressure and time were used: 10 mbar × 50 s, 25 mbar × 20 s, 50 mbar × 10 s, 125 mbar × 4 s, and 250 mbar × 2 s. Despite the constraints posed by the flowrates of the peristaltic pump and the solenoid valve, the microcontroller effectively conducted the injections across this extensive range of conditions, resulting in an IoP RSD of 2.7%.
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Affiliation(s)
- Eric Tavares da Costa
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Claudimir Lucio do Lago
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
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Krebs F, Zagst H, Stein M, Ratih R, Minkner R, Olabi M, Hartung S, Scheller C, Lapizco-Encinas BH, Sänger-van de Griend C, García CD, Wätzig H. Strategies for capillary electrophoresis: Method development and validation for pharmaceutical and biological applications-Updated and completely revised edition. Electrophoresis 2023; 44:1279-1341. [PMID: 37537327 DOI: 10.1002/elps.202300158] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Accepted: 07/19/2023] [Indexed: 08/05/2023]
Abstract
This review is in support of the development of selective, precise, fast, and validated capillary electrophoresis (CE) methods. It follows up a similar article from 1998, Wätzig H, Degenhardt M, Kunkel A. "Strategies for capillary electrophoresis: method development and validation for pharmaceutical and biological applications," pointing out which fundamentals are still valid and at the same time showing the enormous achievements in the last 25 years. The structures of both reviews are widely similar, in order to facilitate their simultaneous use. Focusing on pharmaceutical and biological applications, the successful use of CE is now demonstrated by more than 600 carefully selected references. Many of those are recent reviews; therefore, a significant overview about the field is provided. There are extra sections about sample pretreatment related to CE and microchip CE, and a completely revised section about method development for protein analytes and biomolecules in general. The general strategies for method development are summed up with regard to selectivity, efficiency, precision, analysis time, limit of detection, sample pretreatment requirements, and validation.
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Affiliation(s)
- Finja Krebs
- Institute, of Medicinal and Pharmaceutical Chemistry, Technische Universität Braunschweig, Braunschweig, Lower Saxony, Germany
| | - Holger Zagst
- Institute, of Medicinal and Pharmaceutical Chemistry, Technische Universität Braunschweig, Braunschweig, Lower Saxony, Germany
| | - Matthias Stein
- Institute, of Medicinal and Pharmaceutical Chemistry, Technische Universität Braunschweig, Braunschweig, Lower Saxony, Germany
| | - Ratih Ratih
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Surabaya, Surabaya, East Java, Indonesia
| | - Robert Minkner
- Institute, of Medicinal and Pharmaceutical Chemistry, Technische Universität Braunschweig, Braunschweig, Lower Saxony, Germany
| | - Mais Olabi
- Institute, of Medicinal and Pharmaceutical Chemistry, Technische Universität Braunschweig, Braunschweig, Lower Saxony, Germany
| | - Sophie Hartung
- Institute, of Medicinal and Pharmaceutical Chemistry, Technische Universität Braunschweig, Braunschweig, Lower Saxony, Germany
| | - Christin Scheller
- Institute, of Medicinal and Pharmaceutical Chemistry, Technische Universität Braunschweig, Braunschweig, Lower Saxony, Germany
| | - Blanca H Lapizco-Encinas
- Department of Biomedical Engineering, Kate Gleason College of Engineering, Rochester Institute of Technology, Rochester, New York, USA
| | - Cari Sänger-van de Griend
- Kantisto BV, Baarn, The Netherlands
- Department of Medicinal Chemistry, Faculty of Pharmacy, Uppsala Universitet, Uppsala, Sweden
| | - Carlos D García
- Department of Chemistry, Clemson University, Clemson, South Carolina, USA
| | - Hermann Wätzig
- Institute, of Medicinal and Pharmaceutical Chemistry, Technische Universität Braunschweig, Braunschweig, Lower Saxony, Germany
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Vaghef-Koodehi A, Ernst OD, Lapizco-Encinas BH. Separation of Cells and Microparticles in Insulator-Based Electrokinetic Systems. Anal Chem 2023; 95:1409-1418. [PMID: 36599093 DOI: 10.1021/acs.analchem.2c04366] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Presented here is the first continuous separation of microparticles and cells of similar characteristics employing linear and nonlinear electrokinetic phenomena in an insulator-based electrokinetic (iEK) system. By utilizing devices with insulating features, which distort the electric field distribution, it is possible to combine linear and nonlinear EK phenomena, resulting in highly effective separation schemes that leverage the new advancements in nonlinear electrophoresis. This work combines mathematical modeling and experimentation to separate four distinct binary mixtures of particles and cells. A computational model with COMSOL Multiphysics was used to predict the retention times (tR,p) of the particles and cells in iEK devices. Then, the experimental separations were carried out using the conditions identified with the model, where the experimental retention time (tR,e) of the particles and cells was measured. A total of four distinct separations of binary mixtures were performed by increasing the level of difficulty. For the first separation, two types of polystyrene microparticles, selected to mimic Escherichia coli and Saccharomyces cerevisiae cells, were separated. By leveraging the knowledge gathered from the first separation, a mixture of cells of distinct domains and significant size differences, E. coli and S. cerevisiae, was successfully separated. The third separation also featured cells of different domains but closer in size: Bacillus cereus versus S. cerevisiae. The last separation included cells in the same domain and genus, B. cereus versus Bacillus subtilis. Separation results were evaluated in terms of number of plates (N) and separation resolution (Rs), where Rs values for all separations were above 1.5, illustrating complete separations. Experimental results were in agreement with modeling results in terms of retention times, with deviations in the 6-27% range, while the variation between repetitions was between 2 and 18%, demonstrating good reproducibility. This report is the first prediction of the retention time of cells in iEK systems.
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Affiliation(s)
- Alaleh Vaghef-Koodehi
- Microscale Bioseparations Laboratory and Biomedical Engineering Department, Rochester Institute of Technology, 160 Lomb Memorial Drive, Rochester, New York14623, United States
| | - Olivia D Ernst
- Microscale Bioseparations Laboratory and Biomedical Engineering Department, Rochester Institute of Technology, 160 Lomb Memorial Drive, Rochester, New York14623, United States
| | - Blanca H Lapizco-Encinas
- Microscale Bioseparations Laboratory and Biomedical Engineering Department, Rochester Institute of Technology, 160 Lomb Memorial Drive, Rochester, New York14623, United States
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Miller A, Hill N, Hakim K, Lapizco-Encinas BH. Fine-Tuning Electrokinetic Injections Considering Nonlinear Electrokinetic Effects in Insulator-Based Devices. MICROMACHINES 2021; 12:mi12060628. [PMID: 34071691 PMCID: PMC8227112 DOI: 10.3390/mi12060628] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/28/2021] [Revised: 05/24/2021] [Accepted: 05/25/2021] [Indexed: 12/17/2022]
Abstract
The manner of sample injection is critical in microscale electrokinetic (EK) separations, as the resolution of a separation greatly depends on sample quality and how the sample is introduced into the system. There is a significant wealth of knowledge on the development of EK injection methodologies that range from simple and straightforward approaches to sophisticated schemes. The present study focused on the development of optimized EK sample injection schemes for direct current insulator-based EK (DC-iEK) systems. These are microchannels that contain arrays of insulating structures; the presence of these structures creates a nonuniform electric field distribution when a potential is applied, resulting in enhanced nonlinear EK effects. Recently, it was reported that the nonlinear EK effect of electrophoresis of the second kind plays a major role in particle migration in DC-iEK systems. This study presents a methodology for designing EK sample injection schemes that consider the nonlinear EK effects exerted on the particles being injected. Mathematical modeling with COMSOL Multiphysics was employed to identify proper voltages to be used during the EK injection process. Then, a T-microchannel with insulating posts was employed to experimentally perform EK injection and separate a sample containing two types of similar polystyrene particles. The quality of the EK injections was assessed by comparing the resolution (Rs) and number of plates (N) of the experimental particle separations. The findings of this study establish the importance of considering nonlinear EK effects when planning for successful EK injection schemes.
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7
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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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8
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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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9
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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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10
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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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11
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Freitas CB, Moreira RC, de Oliveira Tavares MG, Coltro WK. Monitoring of nitrite, nitrate, chloride and sulfate in environmental samples using electrophoresis microchips coupled with contactless conductivity detection. Talanta 2016; 147:335-41. [DOI: 10.1016/j.talanta.2015.09.075] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Revised: 09/29/2015] [Accepted: 09/30/2015] [Indexed: 10/22/2022]
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12
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Segato TP, Bhakta SA, Gordon M, Carrilho E, Willis PA, Jiao H, Garcia CD. Microfab-less Microfluidic Capillary Electrophoresis Devices. ANALYTICAL METHODS : ADVANCING METHODS AND APPLICATIONS 2013; 5:1652-1657. [PMID: 23585815 PMCID: PMC3622270 DOI: 10.1039/c3ay26392d] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Compared to conventional bench-top instruments, microfluidic devices possess advantageous characteristics including great portability potential, reduced analysis time (minutes), and relatively inexpensive production, putting them on the forefront of modern analytical chemistry. Fabrication of these devices, however, often involves polymeric materials with less-than-ideal surface properties, specific instrumentation, and cumbersome fabrication procedures. In order to overcome such drawbacks, a new hybrid platform is proposed. The platform is centered on the use of 5 interconnecting microfluidic components that serve as the injector or reservoirs. These plastic units are interconnected using standard capillary tubing, enabling in-channel detection by a wide variety of standard techniques, including capacitively-coupled contactless conductivity detection (C4D). Due to the minimum impact on the separation efficiency, the plastic microfluidic components used for the experiments discussed herein were fabricated using an inexpensive engraving tool and standard Plexiglas. The presented approach (named 52-platform) offers a previously unseen versatility: enabling the assembly of the platform within minutes using capillary tubing that differs in length, diameter, or material. The advantages of the proposed design are demonstrated by performing the analysis of inorganic cations by capillary electrophoresis on soil samples from the Atacama Desert.
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Affiliation(s)
- Thiago P. Segato
- Instituto de Quimica de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil
| | - Samir A. Bhakta
- Department of Chemistry, UT San Antonio, San Antonio, TX, USA
| | - Matthew Gordon
- Department of Chemistry, UT San Antonio, San Antonio, TX, USA
| | - Emanuel Carrilho
- Instituto de Quimica de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil
| | | | - Hong Jiao
- HJ Science & Technology, Santa Clara, CA, USA
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13
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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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14
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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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15
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Sun X, Kelly RT, Danielson WF, Agrawal N, Tang K, Smith RD. Hydrodynamic injection with pneumatic valving for microchip electrophoresis with total analyte utilization. Electrophoresis 2011; 32:1610-8. [PMID: 21520147 DOI: 10.1002/elps.201000522] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Revised: 12/01/2010] [Accepted: 12/29/2010] [Indexed: 11/06/2022]
Abstract
A novel hydrodynamic injector that is directly controlled by a pneumatic valve has been developed for reproducible microchip CE separations. The PDMS devices used for the evaluation comprise a separation channel, a side channel for sample introduction, and a pneumatic valve aligned at the intersection of the channels. A low pressure (≤ 3 psi) applied to the sample reservoir is sufficient to drive sample into the separation channel. The rapidly actuated pneumatic valve enables injection of discrete sample plugs as small as ~ 100 pL for CE separation. The injection volume can be easily controlled by adjusting the intersection geometry, the solution back pressure, and the valve actuation time. Sample injection could be reliably operated at different frequencies (< 0.1 Hz to > 2 Hz) with good reproducibility (peak height relative standard deviation ≤ 3.6%) and no sampling biases associated with the conventional electrokinetic injections. The separation channel was dynamically coated with a cationic polymer, and FITC-labeled amino acids were employed to evaluate the CE separation. Highly efficient (≥ 7.0 × 10³ theoretical plates for the ~2.4-cm-long channel) and reproducible CE separations were obtained. The demonstrated method has numerous advantages compared with the conventional techniques, including repeatable and unbiased injections, little sample waste, high duty cycle, controllable injected sample volume, and fewer electrodes with no need for voltage switching. The prospects of implementing this injection method for coupling multidimensional separations for multiplexing CE separations and for sample-limited bioanalyses are discussed.
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Affiliation(s)
- Xuefei Sun
- Biological Sciences Division and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA
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16
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Guan Q, Henry CS. Improving MCE with electrochemical detection using a bubble cell and sample stacking techniques. Electrophoresis 2009; 30:3339-46. [PMID: 19802848 PMCID: PMC3005344 DOI: 10.1002/elps.200900316] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Two efforts to improve the sensitivity and limits of detection for MCE with electrochemical detection are presented here. One is the implementation of a capillary expansion (bubble cell) at the detection zone to increase the exposed working electrode surface area. Bubble cell widths were varied from 1x to 10x the separation channel width (50 mum) to investigate the effects of electrode surface area on detection sensitivity, LOD, and separation efficiency. Improved detection sensitivity and decreased detection limits were obtained with increased bubble cell width, and LODs of dopamine and catechol detected in a 5x bubble cell were 25 and 50 nM, respectively. Meanwhile, fluorescent imaging results demonstrated approximately 8 and approximately 12% loss in separation efficiency in 4x and 5x bubble cell, respectively. Another effort at reducing the LOD involves using field amplified sample injection for gated injection and field amplified sample stacking for hydrodynamic injection. Stacking effects are shown for both methods using amperometric detection and pulsed amperometric detection. The LODs of dopamine in a 4x bubble cell were 8 and 20 nM using field amplified sample injection and field amplified sample stacking, respectively. However, improved LODs were not obtained for anionic analytes using either stacking technique.
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Affiliation(s)
- Qian Guan
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
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17
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Abstract
Highly efficient preconcentration is a crucial prerequisite to the identification of important protein biomarkers with extremely low abundance in target biofluids. In this work, poly(dimethylsiloxane) microchips integrated with 10 nm polycarbonate nanopore membranes were utilized as high-speed protein accumulators. Double-sided injection control of electrokinetic fluid flow in the sample channel resulted in highly localized protein accumulation at a very sharp point in the channel cross point. This greatly enhanced the ability to detect very low levels of initial protein concentration. Fluorescein labeled human serum albumin solutions of 30 and 300 pM accumulated to 3 and 30 microM in only 100 s. Initial solutions as low as 0.3 and 3 pM could be concentrated within 200 s to 0.3 and 3 microM, respectively. This demonstrates a approximately 10(5)-10(6) accumulation factor, and an accumulation rate as high as 5000/sec, yielding a >10x improvement over most results reported to date.
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Affiliation(s)
- Dapeng Wu
- Nanoelectronics Lab, University of Cincinnati, Cincinnati, Ohio 45221-0030, USA
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18
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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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19
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Hardiman T, Ewald JC, Lemuth K, Reuss M, Siemann-Herzberg M. Quantification of rRNA in Escherichia coli using capillary gel electrophoresis with laser-induced fluorescence detection. Anal Biochem 2007; 374:79-86. [PMID: 17967436 DOI: 10.1016/j.ab.2007.09.032] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2007] [Revised: 09/17/2007] [Accepted: 09/25/2007] [Indexed: 12/31/2022]
Abstract
Over the past 10 years, sophisticated powerful techniques have been developed for the quantification of messenger RNA (mRNA) and ribosomal RNA (rRNA), enabling researchers in science, industry, and molecular medicine to explore gene expression. These techniques require the (reverse) transcription of analyte RNA, hybridization with synthetic oligonucleotides, and other additional steps that make them costly, time-consuming, and quantitatively difficult to perform. The current work demonstrates how 16S and 23S rRNA can be quantified precisely using capillary gel electrophoresis with laser-induced fluorescence detection (CGE-LIF) directly after the extraction of total RNA without requiring further reactions or calibration. CGE-LIF normally is used for the qualitative examination of RNA preparations. Its quantitative performance could be improved significantly using MS2 bacteriophage RNA as an internal standard. The entire analytical procedure was validated for linearity, repeatability, reproducibility, and recovery. This validation also included total RNA extraction from bacterial cells, an aspect examined for the first time in absolute RNA quantification. Recovery is close to 100%, and the analytical precision was increased 10-fold (CV<3%), as compared with similar approaches. The demonstrated method is simple and opens up new possibilities for the absolute quantification of not only rRNA but also individual mRNAs.
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Affiliation(s)
- Timo Hardiman
- Institute of Biochemical Engineering, University of Stuttgart, D-70569 Stuttgart, Germany
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