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Li M, Tong Z, Gao X, Zhang L, Li S. Simultaneous detection of zearalenone, citrinin, and ochratoxin A in pepper by capillary zone electrophoresis. Food Addit Contam Part A Chem Anal Control Expo Risk Assess 2020; 37:1388-1398. [PMID: 32546103 DOI: 10.1080/19440049.2020.1769197] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
In the present study, a simple and fast method for simultaneous detection of zearalenone, citrinin, and ochratoxin A utilising capillary zone electrophoresis with an ultraviolet detector was developed. The optimised approach was validated and applied using pepper samples. The proposed method yielded satisfactory linearity between the signal and the mycotoxin concentration in the range of 1.5-150 μg/kg for zearalenone, 4.5-150 μg/kg for citrinin, and 0.8-150 μg/kg for ochratoxin A. The limits of detection for these mycotoxins ranged from 0.3 to 1.5 μg/kg. The corresponding intra- and inter-day precisions were less than 3.5 % and 4.1 %, respectively. Moreover, the matrix effect was also assessed and the result was compared using the capillary zone electrophoresis and high-performance liquid chromatography methods. The developed approach could be used for simultaneous detection of zearalenone, citrinin, and ochratoxin A in pepper.
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Affiliation(s)
- Minghui Li
- Key Laboratory of Chemical Utilization of Forestry Biomass of Zhejiang Province, Zhejiang A & F University , Hangzhou, Zhejiang Province, P. R. China
| | - Zaikang Tong
- Key Laboratory of Chemical Utilization of Forestry Biomass of Zhejiang Province, Zhejiang A & F University , Hangzhou, Zhejiang Province, P. R. China
| | - Xingjun Gao
- Key Laboratory of Chemical Utilization of Forestry Biomass of Zhejiang Province, Zhejiang A & F University , Hangzhou, Zhejiang Province, P. R. China
| | - Lijun Zhang
- Key Laboratory of Chemical Utilization of Forestry Biomass of Zhejiang Province, Zhejiang A & F University , Hangzhou, Zhejiang Province, P. R. China
| | - Sha Li
- Key Laboratory of Chemical Utilization of Forestry Biomass of Zhejiang Province, Zhejiang A & F University , Hangzhou, Zhejiang Province, P. R. China
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2
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Mani NK, Das SS, Dawn S, Chakraborty S. Electro-kinetically driven route for highly sensitive blood pathology on a paper-based device. Electrophoresis 2020; 41:615-620. [PMID: 31891191 DOI: 10.1002/elps.201900356] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2019] [Revised: 10/30/2019] [Accepted: 12/23/2019] [Indexed: 12/15/2022]
Abstract
Enhancing the sensitivity of colorimetric detection in paper-devices is a quintessential step in achieving frugal diagnosis. Here, we demonstrate an effective way of improving the detection sensitivity of paper-based devices, as mediated by electro-kinetic mechanisms. By directly employing blood plasma, we investigate the electro-kinetic clustering of glucose, a neutral molecule in paper devices. Under the influence of uniform electric field, dispersed glucose gets accumulated in the paper strips. Due to the combination of EOF and electrophoretic migration, we achieve twofold increase in the colour intensity for both normal and diabetic samples. This approach is robust and possesses better sensitivity than conventional colorimetric assays and can be easily extended to other body fluid based diagnosis. These results may turn out to be of profound importance in improving the quality of pathological diagnosis in low-cost paper-based point-of-care devices deployed in resource-limited settings.
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Affiliation(s)
- Naresh Kumar Mani
- Department of Biotechnology, Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal, Karnataka, India
- Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur, India
| | - Sankha Shuvra Das
- Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur, India
| | - Sayantan Dawn
- Department of Mechanical Engineering, Jadavpur University, Kolkata, India
| | - Suman Chakraborty
- Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur, India
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3
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Baron D, Cacho C, Petr J. Electrokinetic preconcentration of magnetite core – carboxylic shell nanoparticles by capillary electrophoresis. J Chromatogr A 2017; 1499:217-221. [DOI: 10.1016/j.chroma.2017.03.079] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 03/27/2017] [Accepted: 03/28/2017] [Indexed: 12/18/2022]
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4
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Food Microfluidics Biosensors. BIOSENSORS FOR SUSTAINABLE FOOD - NEW OPPORTUNITIES AND TECHNICAL CHALLENGES 2016. [DOI: 10.1016/bs.coac.2016.04.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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5
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Fayad S, Nehmé R, Lafite P, Morin P. Assaying human neutrophil elastase activity by capillary zone electrophoresis combined with laser-induced fluorescence. J Chromatogr A 2015; 1419:116-24. [DOI: 10.1016/j.chroma.2015.09.084] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Revised: 09/11/2015] [Accepted: 09/26/2015] [Indexed: 01/19/2023]
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6
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Breadmore MC, Tubaon RM, Shallan AI, Phung SC, Abdul Keyon AS, Gstoettenmayr D, Prapatpong P, Alhusban AA, Ranjbar L, See HH, Dawod M, Quirino JP. Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2012-2014). Electrophoresis 2015; 36:36-61. [DOI: 10.1002/elps.201400420] [Citation(s) in RCA: 132] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Revised: 09/25/2014] [Accepted: 09/25/2014] [Indexed: 12/15/2022]
Affiliation(s)
- Michael C. Breadmore
- School of Physical Science; Australian Centre of Research on Separation Science, University of Tasmania; Hobart Tasmania Australia
| | - Ria Marni Tubaon
- School of Physical Science; Australian Centre of Research on Separation Science, University of Tasmania; Hobart Tasmania Australia
| | - Aliaa I. Shallan
- School of Physical Science; Australian Centre of Research on Separation Science, University of Tasmania; Hobart Tasmania Australia
| | - Sui Ching Phung
- School of Physical Science; Australian Centre of Research on Separation Science, University of Tasmania; Hobart Tasmania Australia
| | - Aemi S. Abdul Keyon
- School of Physical Science; Australian Centre of Research on Separation Science, University of Tasmania; Hobart Tasmania Australia
- Faculty of Science; Department of Chemistry, Universiti Teknologi Malaysia; Johor Malaysia
| | - Daniel Gstoettenmayr
- School of Physical Science; Australian Centre of Research on Separation Science, University of Tasmania; Hobart Tasmania Australia
| | - Pornpan Prapatpong
- Faculty of Pharmacy; Department of Pharmaceutical Chemistry, Mahidol University; Rajathevee Bangkok Thailand
| | - Ala A. Alhusban
- Faculty of Health Sciences, School of Pharmacy; Australian Centre of Research on Separation Science, University of Tasmania; Hobart Tasmania Australia
| | - Leila Ranjbar
- School of Physical Science; Australian Centre of Research on Separation Science, University of Tasmania; Hobart Tasmania Australia
| | - Hong Heng See
- School of Physical Science; Australian Centre of Research on Separation Science, University of Tasmania; Hobart Tasmania Australia
- Ibnu Sina Institute for Fundamental Science Studies; Universiti Teknologi Malaysia; Johor Malaysia
| | - Mohamed Dawod
- Department of Chemistry; University of Michigan; Ann Arbor MI USA
- Faculty of Pharmacy; Department of Analytical Chemistry, Al-Azhar University; Cairo Egypt
| | - Joselito P. Quirino
- School of Physical Science; Australian Centre of Research on Separation Science, University of Tasmania; Hobart Tasmania Australia
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7
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Rabanes HR, Quirino JP. Sweeping of alprenolol enantiomers with an organic solvent and sulfated β-cyclodextrin in capillary electrophoresis. Electrophoresis 2013; 34:1319-26. [DOI: 10.1002/elps.201200595] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Revised: 01/11/2013] [Accepted: 02/18/2013] [Indexed: 11/10/2022]
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8
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Ríos Á, Ríos Á, Zougagh M, Zougagh M. Sample preparation for micro total analytical systems (μ-TASs). Trends Analyt Chem 2013. [DOI: 10.1016/j.trac.2012.12.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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9
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Cao C, Zhang W, Fan L, Shao J, Li S. Comparative study on sample stacking by moving reaction boundary formed with weak acid and weak or strong alkali in capillary electrophoresis. Talanta 2011; 84:651-8. [DOI: 10.1016/j.talanta.2011.01.059] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Revised: 01/14/2011] [Accepted: 01/21/2011] [Indexed: 10/18/2022]
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10
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Mikus P, Maráková K. Advanced CE for chiral analysis of drugs, metabolites, and biomarkers in biological samples. Electrophoresis 2010; 30:2773-802. [PMID: 19653234 DOI: 10.1002/elps.200900173] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
An analysis of recent trends indicates that CE can show real advantages over chromatographic methods in ultratrace enantioselective determination of biologically active compounds in complex biological matrices. It is due to high separation efficiency and many applicable in-capillary electromigration effects in CE (countercurrent migration, stacking effects) enhancing significantly (enantio)separability and enabling effective sample preparation (preconcentration, purification, analyte derivatization). Other possible on-line combinations of CE, such as column coupled CE-CE techniques and implementation of nonelectrophoretic techniques (extraction, membrane filtration, flow injection) into CE, offer additional approaches for highly effective sample preparation and separation. CE matured to a highly flexible and compatible technique enabling its hyphenation with powerful detection systems allowing extremely sensitive detection (e.g. LIF) and/or structural characterization of analytes (e.g. MS). Within the last decade, more as well as less conventional analytical on-line approaches have been effectively utilized in this field and their practical potentialities are demonstrated on many new application examples in this article. Here, three basic areas of (enantioselective) drug bioanalysis are highlighted and supported by a brief theoretical description of each individual approach in a compact review structure (to create integrated view on the topic), including (i) progressive enantioseparation approaches and new enantioselective agents, (ii) in-capillary sample preparation (preconcentration, purification, derivatization), and (iii) detection possibilities related to enhanced sensitivity and structural characterization.
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Affiliation(s)
- Peter Mikus
- Department of Pharmaceutical Analysis and Nuclear Pharmacy, Faculty of Pharmacy, Comenius University, Bratislava, Slovak Republic.
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11
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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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12
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Pan Q, Zhao M, Liu S. Combination of on-chip field amplification and bovine serum albumin sweeping for ultrasensitive detection of green fluorescent protein. Anal Chem 2009; 81:5333-41. [PMID: 19492801 DOI: 10.1021/ac9007607] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report a highly effective on-chip preconcentration method by combining field-amplified sample injection (FASI) and bovine serum albumin (BSA) sweeping for ultrasensitive detection of green fluorescent protein (GFP) on a simple cross-channel microchip device. With the formation of a stagnant sample/running buffer boundary by balancing the hydrodynamic flow and the electro-osmotic flow (EOF), GFP molecules can be continuously injected into the sample loading channel and stacked. We have also demonstrated that BSA is a very effective pseudo-stationary phase for sweeping concentration of proteins in comparison to the commonly used micelles. The combination of FASI and BSA sweeping yields a concentration factor of 3570 and a limit of detection of 8.4 pM for GFP. Using this method, we have separated GFP and GFP-insulin-like growth factor-I (GFP-IGF-I) fusion protein. The entire assay (GFP concentration, matrix elimination, and electrophoretic separation) can be completed within <5 min. Furthermore, we have successfully applied this method for the detection of GFP expression of E. coli cells and the GFP content in single E. coli cells.
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Affiliation(s)
- Qiong Pan
- Key Laboratory of Bioorganic Chemistry & Molecular Engineering of Ministry of Education, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, People's Republic of China
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13
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Shen S, Li Y, Wakida SI, Takeda S. Determination of adrenal steroids by microfluidic chip using micellar electrokinetic chromatography. ENVIRONMENTAL MONITORING AND ASSESSMENT 2009; 153:201-208. [PMID: 18551375 DOI: 10.1007/s10661-008-0349-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2007] [Accepted: 04/14/2008] [Indexed: 05/26/2023]
Abstract
This paper describes a sensitive and convenient method to separate progesterone, 17alpha-hydroxy progesterone, cortexolone, hydrocortisone and cortisone, all of which are steroids and have similar structures, using microfluidic chip-based technology with UV detection at 252 nm. We successfully obtained high-speed separation of the five steroids within 70 s in optimized microfluidic controls and micellar electrokinetic chromatography (MEKC) separation conditions. Fairly good linearity with correlation coefficient of over 0.98 from 10 or 20 to 100 mg/l steroid chemicals was obtained. The limits of detection obtained at a signal to noise ratio of 3 were from 3.89 to 7.80 mg/l. The values of the relative standard deviation (RSD) were 0.98-1.34% for repetitive injection (n = 12) and the intraday and interday RSDs were below 6%. The highly stable response reflected the feasibility of this method.
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Affiliation(s)
- Shuanglong Shen
- Department of Chemistry, Changzhi College, 73 Chengbei East Street, Changzhi, 046011 Shanxi, China
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14
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Jin J, Shao J, Li S, Zhang W, Fan LY, Cao CX. Computer simulation on a continuous moving chelation boundary in ethylenediaminetetraacetic acid-based sample sweeping in capillary electrophoresis. J Chromatogr A 2009; 1216:4913-22. [DOI: 10.1016/j.chroma.2009.04.038] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Revised: 03/19/2009] [Accepted: 04/14/2009] [Indexed: 12/01/2022]
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15
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Xie HY, He YZ, Gan WE, Fu GN, Li L, Han F, Gao Y. On-column liquid–liquid–liquid microextraction coupled with base stacking as a dual preconcentration method for capillary zone electrophoresis. J Chromatogr A 2009; 1216:3353-9. [DOI: 10.1016/j.chroma.2009.01.070] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2008] [Revised: 01/17/2009] [Accepted: 01/23/2009] [Indexed: 10/21/2022]
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16
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Cao J, Qi LW, Chen J, Li P. Pressure and electrokinetic injections for on-line sample stacking neutral analytes in microemulsion electrokinetic chromatography with salt-containing matrixes. Electrophoresis 2009; 29:4422-30. [PMID: 18942679 DOI: 10.1002/elps.200800190] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
An on-line technique for pressure and electrokinetic injections of long sample plugs with simultaneous stacking of neutral analytes (notoginsenoside R(1), ginsenoside Rg(1), ginsenoside Rf, ginsenoside Rh(1), ginsenoside Rd, ginsenoside Rg3) in microemulsion electrokinetic chromatography is presented. The effects of salt concentration, sample plug length, organic modification of the sample matrix, oil phase and SDS concentration on stacking efficiency were examined in order to optimize the two injection methods. In microemulsion electrokinetic chromatography, the effect of the type of oil and SDS content on stacking mechanism is often sophisticated. This study had demonstrated that the oil type and SDS content in microemulsion indeed markedly altered the affinity of microemulsion with analytes. Finally, in comparison with the electrokinetic injection method, the most apparent disadvantages of the pressure injection method were the relatively high LOD and poor reproducibility.
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Affiliation(s)
- Jun Cao
- Key Laboratory of Modern Chinese Medicines (China Pharmaceutical University), Ministry of Education, Nanjing, PR China
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17
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Proczek G, Augustin V, Descroix S, Hennion MC. Integrated microdevice for preconcentration and separation of a wide variety of compounds by electrochromatography. Electrophoresis 2009; 30:515-24. [DOI: 10.1002/elps.200800308] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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18
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Terabe S. Capillary separation: micellar electrokinetic chromatography. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2009; 2:99-120. [PMID: 20636055 DOI: 10.1146/annurev.anchem.1.031207.113005] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Micellar electrokinetic chromatography (MEKC), a separation mode of capillary electrophoresis (CE), has enabled the separation of electrically neutral analytes. MEKC can be performed by adding an ionic micelle to the running solution of CE without modifying the instrument. Its separation principle is based on the differential migration of the ionic micelles and the bulk running buffer under electrophoresis conditions and on the interaction between the analyte and the micelle. Hence, MEKC's separation principle is similar to that of chromatography. MEKC is a useful technique particularly for the separation of small molecules, both neutral and charged, and yields high-efficiency separation in a short time with minimum amounts of sample and reagents. To improve the concentration sensitivity of detection, several on-line sample preconcentration techniques such as sweeping have been developed.
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Affiliation(s)
- Shigeru Terabe
- Graduate School of Material Science, University of Hyogo, Kamigori, Hyogo 678-1297, Japan.
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Sueyoshi K, Kitagawa F, Otsuka K. Recent progress of online sample preconcentration techniques in microchip electrophoresis. J Sep Sci 2008; 31:2650-66. [PMID: 18693308 DOI: 10.1002/jssc.200800272] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Microchip electrophoresis (MCE) has been advanced remarkably by the applications of several separation modes and the integration with several chemical operations on a single planer substrate. MCE shows superior analytical performance, e.g., high-speed analysis, high resolution, low consumption of reagents, and so on, whereas low-concentration sensitivity is still one of the major problems. To overcome this drawback, various online sample preconcentration techniques have been developed in MCE over the past 15 years, which have successfully enhanced the detection sensitivity in MCE. This review highlights recent developments in online sample preconcentration in MCE categorized on the basis of "dynamic" and "static" methods. The dynamic techniques including field amplified stacking, ITP, sweeping, and focusing have been easily applied to MCE, which provide effective enrichments of various analytes. The static techniques such as SPE and filtration have also been combined with MCE. In the static techniques, extremely high preconcentration efficiency can be obtained, compared to the dynamic methods. This review provides comprehensive tables listing the applications and sensitivity enhancement factors of these preconcentration techniques employed in MCE.
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Affiliation(s)
- Kenji Sueyoshi
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan.
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20
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Electrokinetic sample injection for high‐sensitivity capillary zone electrophoresis (part 1): Effects of electrode configuration and setting. Electrophoresis 2008; 29:3786-93. [DOI: 10.1002/elps.200800172] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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21
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Nagata H, Ishikawa M, Yoshida Y, Tanaka Y, Hirano K. Use of a heterogeneous buffer combination in microchip electrophoresis for high‐resolution separation by on‐line concentration of DNA samples. Electrophoresis 2008; 29:3744-51. [DOI: 10.1002/elps.200800143] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Hideya Nagata
- Health Technology Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Takamatsu, Japan
| | - Mitsuru Ishikawa
- Health Technology Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Takamatsu, Japan
| | - Yuichiro Yoshida
- Health Technology Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Takamatsu, Japan
| | - Yoshio Tanaka
- Health Technology Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Takamatsu, Japan
| | - Ken Hirano
- Health Technology Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Takamatsu, Japan
- PRESTO, Japan Science and Technology Agency, Honcho, Kawaguchi Saitama, Japan
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22
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Yamamoto S, Hirakawa S, Suzuki S. In situ fabrication of ionic polyacrylamide-based preconcentrator on a simple poly(methyl methacrylate) microfluidic chip for capillary electrophoresis of anionic compounds. Anal Chem 2008; 80:8224-30. [PMID: 18841941 DOI: 10.1021/ac801245n] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A simple and efficient method was developed for fabrication of an anionic sample preconcentrator on a channel of a commercial poly(methyl methacrylate) (PMMA)-made microchip using no photolithography or etching technique. The originality of our preconcentrator is based on simple photochemical copolymerization of monomers using the following procedure: All channels of the PMMA-made microchip were filled with gel solution comprising acrylamide, N,N'-methylene-bisacrylamide, and 2-acrylamide-2-methylpropanesulfonic acid with riboflavin as a photocatalytic initiator. In situ polymerization near the cross of the sample outlet channel was performed by irradiation with an argon ion laser beam, which is also used as the light source for fluorometric detection. The electrokinetic property and electric repulsion between sample components and anionic groups on the polyacrylamide gel layer produce, trap, and concentrate anions within a few minutes at the interface of the cathodic side of the gel layer. This method displays concentration factors as high as 10 (5). The availability of ionic preconcentrator was demonstrated by applying sensitive analysis of oligosaccharides labeled with 8-aminopyrene-1,3,6-trisulfonate and some glycoproteins labeled with fluorescein isothiocyanate under various buffer systems.
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Affiliation(s)
- Sachio Yamamoto
- School of Pharmacy, Kinki University, 3-4-1, Kowakae, Higashi-osaka, Japan
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Improvement of Porous Electro-conductive Membrane Preparation and Its Application in Sample Injection Pre-concentration in the Capillary Electrophoresis of Proteins. CHINESE JOURNAL OF ANALYTICAL CHEMISTRY 2008. [DOI: 10.1016/s1872-2040(08)60047-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Newman CID, Giordano BC, Copper CL, Collins GE. Microchip micellar electrokinetic chromatography separation of alkaloids with UV-absorbance spectral detection. Electrophoresis 2008; 29:803-10. [PMID: 18203247 DOI: 10.1002/elps.200700591] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A microchip device is demonstrated for the electrophoretic separation and UV-absorbance spectral detection of four toxic alkaloids: colchicine, aconitine, strychnine, and nicotine. A fused-silica (quartz) microchip containing a simple cross geometry is utilized to perform the separations, and a miniature, fiber-optic CCD spectrometer is coupled to the microchip for detection. Sensitive UV-absorbance detection is achieved via the application of online preconcentration techniques in combination with the quartz microchip substrate which contains an etched bubble-cell for increased pathlength. The miniature CCD spectrometer is configured to detect light between 190 and 645 nm and LabView programming written in-house enables absorbance spectra as well as separations to be monitored from 210 to 400 nm. Consequently, the configuration of this microchip device facilitates qualitative and quantitative separations via simultaneous spatial and spectral resolution of solutes. UV-absorbance limits of quantification for colchicine, 20 microM (8 mg/L); strychnine, 50 microM (17 mg/L); aconitine, 50 microM (32 mg/L); and nicotine, 100 microM (16 mg/L) are demonstrated on the microchip. With the exception of aconitine, these concentrations are > or =20-times more sensitive than lethal dose monitoring requirements. Finally, this device is demonstrated to successfully detect each toxin in water, skim milk, and apple juice samples spiked at sublethal dose concentrations after a simple, SPE procedure.
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Affiliation(s)
- Carl I D Newman
- Chemistry Division, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, USA
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25
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Matsui T, Franzke J, Manz A, Janasek D. Temperature gradient focusing in a PDMS/glass hybrid microfluidic chip. Electrophoresis 2008; 28:4606-11. [PMID: 18008305 DOI: 10.1002/elps.200700272] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This paper reports the application of temperature gradient focusing (TGF) in a PDMS/glass hybrid microfluidic chip. With TGF, by the combination of a temperature gradient along a microchannel, an applied electric field, and a buffer with a temperature-dependent ionic strength, analytes are focused by balancing their electrophoretic velocities against the bulk velocity of the buffer containing the analytes. In this work, Oregon Green 488 carboxylic acid was concentrated approximately 30 times as high as the initial concentration in 45 s at moderate electric strength of 70 V/cm and a temperature gradient of 55 degrees C across the PDMS/glass hybrid microfluidic chip with a 1 cm long capillary.
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Affiliation(s)
- Takuya Matsui
- ISAS-Institute for Analytical Sciences Dortmund and Berlin, Dortmund, Germany
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26
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Zhang ZX, Zhang XW, Wang JJ, Zhang SS. Sequential preconcentration by coupling of field amplified sample injection with pseudo isotachophoresis-acid stacking for analysis of alkaloids in capillary electrophoresis. Anal Bioanal Chem 2008; 390:1645-52. [PMID: 18228006 DOI: 10.1007/s00216-008-1843-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2007] [Revised: 12/29/2007] [Accepted: 01/08/2008] [Indexed: 10/22/2022]
Abstract
A novel on-column sequential preconcentration method based on the combination of field-amplified sample injection induced by acetonitrile and pseudo isotachophoresis (ITP)-acid stacking is developed for simply but efficiently concentrating alkaloid cations in a high-salt sample matrix in capillary electrophoresis. Acetonitrile (70%) added to a sample solution with a high-salt sample matrix not only induces field-amplified sample stacking by decreasing conductivity but also acts as a termination reagent in the succeeding pseudo ITP. After sample injection had been completed, a plug of H(+) was injected electrokinetically and a neutralization reaction between H(+) and tartrate from the buffer solution produced a low conductivity zone, in which the injected analyte cations were further concentrated. With the sequential preconcentration method, a 3 orders of magnitude detection sensitivity (1,400-fold) increase could be observed compared with the conventional electrokinetic injection method, without compromising separation efficiency and peak shape, and detection limits of 0.1 ng/mL for myosmine and 0.3 ng/mL for anabasine with the conditions selected were achieved. The calibration curves demonstrated good linearity in the concentration ranges 1.3-600 ng/mL for myosmine and 4.9-900 ng/mL for anabasine, respectively. The proposed method has been used to analyze successfully trace alkaloids in cigarette samples.
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Affiliation(s)
- Zhao-Xiang Zhang
- Key Laboratory of Eco-chemical Engineering, Ministry of Education, College of Chemistry and Molecular Engineering, Qingdao University of Science Technology, Qingdao, 266042, China
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27
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Simpson SL, Quirino JP, Terabe S. On-line sample preconcentration in capillary electrophoresis. J Chromatogr A 2008; 1184:504-41. [DOI: 10.1016/j.chroma.2007.11.001] [Citation(s) in RCA: 269] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2007] [Revised: 10/30/2007] [Accepted: 11/01/2007] [Indexed: 02/06/2023]
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28
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Fang H, Yang F, Sun J, Zeng Z, Xu Y. Pressure-assisted field-amplified sample injection with reverse migrating micelles for analyzing trace steroids in MEKC. Electrophoresis 2008; 28:3697-704. [PMID: 17899536 DOI: 10.1002/elps.200700210] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
This paper describes a novel method that applies pressure-assisted field-amplified sample injection with reverse migrating micelles (PA-FASI-RMM) for the online concentration of neutral analytes in MEKC with a low-pH BGE. After injection of a plug of water into the separation capillary, negative voltage and positive pressure were simultaneously applied to initialize PA-FASI-RMM injection. The hydrodynamic flow generated by the positive pressure compensated the reverse EOF in the water plug and allowed the water plug to remain in the capillary during FASI with reverse migrating micelles (FASI-RMM) to obtain a much longer injection time than usual, which improved stacking efficiency greatly. Equations describing this injection mode were introduced and were supported by experimental results. For a 450-s online PA-FASI-RMM injection, three orders of magnitude sample enhancement in terms of peak area could be observed for the steroids and an achievement of detection limits was between 1 and 10 ng/mL.
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Affiliation(s)
- Huaifang Fang
- Department of Chemistry, Wuhan University, Wuhan, People's Republic of China
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29
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Busnel JM, Le Saux T, Descroix S, Girault HH, Hennion MC, Terabe S, Peltre G. Integration of various stacking processes in carrier ampholyte-based capillary electrophoresis. J Chromatogr A 2008; 1182:226-32. [DOI: 10.1016/j.chroma.2007.12.079] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2007] [Revised: 12/10/2007] [Accepted: 12/27/2007] [Indexed: 11/16/2022]
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30
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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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31
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Determination of 3-Nitrotyrosine by Micellar Electrokinetic Chromatography with on-Column High-Salt Stacking. CHINESE JOURNAL OF ANALYTICAL CHEMISTRY 2007. [DOI: 10.1016/s1872-2040(07)60069-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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32
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Breadmore MC. Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips. Electrophoresis 2007; 28:254-81. [PMID: 17149782 DOI: 10.1002/elps.200600463] [Citation(s) in RCA: 160] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Poor sensitivity is considered to be one of the major limitations of electrophoretic separation methods, particularly when compared to traditional liquid chromatographic techniques. To address this issue, various in-line preconcentration techniques have been developed over the past 15 years, ranging in power and complexity, and there are now a number of well understood approaches routinely capable of providing a 10,000- to 100,000-fold increase in sensitivity, as well as several that can be pushed above a million. Furthermore, these have been achieved with particularly troublesome and often difficult samples, such as those having high salinity from a biological or environmental origin. This review will discuss the most common methods for improving the sensitivity of CE, CEC and microchip version of these, with particular attention to those approaches developed over the last five years.
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Affiliation(s)
- Michael C Breadmore
- Australian Centre for Research on Separation Science, School of Chemistry, University of Tasmania, Hobart, Tasmania, Australia.
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Qu Q, Liu Y, Tang X, Wang C, Yang G, Hu X, Yan C. Etched bare fused-silica capillaries for online preconcentration of amino acids in CE. Electrophoresis 2007; 27:4500-7. [PMID: 17054084 DOI: 10.1002/elps.200600057] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
An online preconcentration method based on electrostatic interaction between the analytes and inner surface of the capillary column was developed for the determination of zwitterionic analytes such as amino acids in CE coupled with a DAD. The amino acids possessed positive charges when they were dissolved in an acidic solvent. When they were injected into the column, they were attracted by the negatively charged inner surface of the fused-silica capillary column. An etched column was used to increase the area of the capillary's inner surface and, consequently increase the electrostatic interaction between the amino acids and the inner surface of the capillary column. It was found that when the sample was injected at 10 psi for 1 min and the pH value of the sample was 4, the amount of amino acids attracted to the inner surface of the capillary was maximum. Under these optimized experimental conditions, the detection sensitivity of CE-DAD was enhanced by 5200, 2800, and 3100 times for asparagine, tryptophan and phenylalanine, respectively, compared with normal CE separation. The method provided good reproducibility in terms of both migration time and peak height. It can be successfully used for the preconcentration zwitterion.
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Affiliation(s)
- Qishu Qu
- Jiangsu Key Laboratory of Environmental Materials and Environmental Engineering, College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, P. R. China.
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34
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Kartsova LA, Bessonova EA. Determination of steroids in biological samples by micellar electrokinetic chromatography. JOURNAL OF ANALYTICAL CHEMISTRY 2007. [DOI: 10.1134/s1061934807010145] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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35
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Chen CC, Yen SF, Makamba H, Li CW, Tsai ML, Chen SH. Semihydrodynamic Injection for High Salt Stacking and Sweeping on Microchip Electrophoresis and Its Application for the Analysis of Estrogen and Estrogen Binding. Anal Chem 2006; 79:195-201. [PMID: 17194139 DOI: 10.1021/ac061377b] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In this work, a semihydrodynamic (SHD) injection method was introduced and coupled with high salt stacking and electrokinetic chromatography for the analysis of estrogen and estrogen binding using a simple cross microchannel. The SHD method allows all samples to be hydrodynamically injected and focused into the separation channel at a relatively high flow rate and without splitting and diffusion, leading to reproducible bias-free injections of larger sample volumes (up to 50 nL) within 3 s. Moreover, the injection method is initiated without voltage switching, leading to a reduced mixing effect. Such advantages are well suited for performing stacking and sweeping on a microchip. We investigated the stacking effect under continuous and discontinuous co-ion conditions as well as under sweeping conditions. Micellar sweeping effect alone was relatively weak (7-8 times), partly due to a lower sodium cholate concentration (30 mM) used for the running buffer. By combining the sweeping effect with high salt stacking, however, up to a 200-300-fold enhancement factor could be achieved, and the high-salt and low-surfactant contents for the running buffer were favorable for binding study under nonequilibrium conditions. To the best of our knowledge, this is the first demonstration of the hydrodynamic injection used for high salt sample stacking on a microchip, also for further combining micellar electrochromatography and affinity separation for the analysis of hydrophobic ligand binding using microchip electrophoresis.
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Affiliation(s)
- Cheng-Chuan Chen
- Department of Chemistry and Department of Physiology, National Cheng Kung University, Tainan, Taiwan
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36
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Huang M, Chang H. Indirect Fluorescence of Amines in Capillary Electrophoresis, Using Cresyl Violet. J LIQ CHROMATOGR R T 2006. [DOI: 10.1081/jlc-120025597] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Ming‐Feng Huang
- a Department of Chemistry , National Taiwan University , Roosevelt Road, Sec. 4, Taipei, 106, Taiwan, R.O.C
| | - Huan‐Tsung Chang
- a Department of Chemistry , National Taiwan University , Roosevelt Road, Sec. 4, Taipei, 106, Taiwan, R.O.C
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37
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Acedo-Valenzuela MI, Galeano-Díaz T, Mora-Díez N, Silva-Rodríguez A. Response surface methodology in the development of a stacking-sensitive capillary electrophoresis method by field-amplified injection for the analysis of tricyclic antidepressants in the presence of salts. J Sep Sci 2006; 29:2091-7. [PMID: 17017024 DOI: 10.1002/jssc.200600068] [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] [Indexed: 11/08/2022]
Abstract
The work presented here explores the possibilities of the electrokinetic injection (EK) to achieve sensitive methods for the determination of tricyclic antidepressants in biological samples (serum). The addition of ACN to the sample, with high content in salts, causes stacking at the tip of the capillary, in a similar way as for hydrodynamic injection. An experimental design with the response surface methodology has been used to find the optimum composition of the matrix of the sample (sodium chloride and ACN percentages) and the conditions for the EK (water-plug length, time, and voltage of injection) in few experiments. The composition of the separation buffer was the same as utilized in a previous paper. The use of a bubble capillary to reach lower detection limits implies a loss of the resolution and requires a new optimization. Finally, a comparison between electrokinetic and hydrodynamic injections is made.
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38
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Song GQ, Peng ZL, Lin JM. Comparison of two capillary electrophoresis online stacking modes by analysis of polycyclic aromatic hydrocarbons in airborne particulates. J Sep Sci 2006; 29:2065-71. [PMID: 17017020 DOI: 10.1002/jssc.200500364] [Citation(s) in RCA: 12] [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
Naphthalene, fluorene, pyrene, anthracene, phenanthrene, and chrysene were successfully separated by CD-modified MEKC (CD-MEKC) using 20 mM borate (pH 9.0) containing 90 mM SDS and 75 mM beta-CD. Two online stacking methods, i.e., sweeping and field-enhanced sample injection (FESI), were explored to enhance the detection sensitivity. The influences of some crucial parameters in sweeping and FESI procedures were investigated. For FESI method, a plug of water and low-conductivity sample matrix was used to increase the stacking efficiency. Compared with the sweeping method, FESI can increase the sensitivity in the range of 10-20-fold. The proposed method was used for the analysis of polycyclic aromatic hydrocarbons in airborne particulates.
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Affiliation(s)
- Guan-Qun Song
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, P. R. China
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39
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Jung B, Bharadwaj R, Santiago JG. On-Chip Millionfold Sample Stacking Using Transient Isotachophoresis. Anal Chem 2006; 78:2319-27. [PMID: 16579615 DOI: 10.1021/ac051659w] [Citation(s) in RCA: 202] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We present a simple and robust isotachophoresis (ITP) method that can be integrated with microchip-based capillary electrophoresis (CE) devices to achieve millionfold sample stacking. We performed an experimental parametric study to show the effects of initial sample ion concentration, leading ion concentration, and trailing ion concentration on ITP stacking. We also discuss the usefulness and limitations of a simple one-dimensional nondispersive model and a scaling analysis for dispersion rate. We found that a single-column ITP configuration together with electroosmotic flow suppression and high leading ion concentration provide high-performance ITP and can be integrated readily with CE separation. We demonstrated detection of trace of 100 fM Alexa Fluor 488 (signal-to-noise ratio of 11) with a concentration increase of a factor of 2 x 10(6). Application of our ITP/CE protocol to the stacking and separation of negatively charged fluorescent tracers (Alexa Fluor 488 and bodipy) resulted in a concentration increase of 6.4 x 10(4) and a signal increase of 4.5 x 10(5). The ITP/CE protocol can be performed with a standard microchannel cross design or simple flow control. The method can be implemented with available off-the-shelf chip systems using off-the-shelf voltage control systems and buffer chemistries.
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Affiliation(s)
- Byoungsok Jung
- Department of Mechanical Engineering, and Department of Chemical Engineering, Stanford University, Stanford, California 94305, USA
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40
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Kumemura M, Korenaga T. Quantitative extraction using flowing nano-liter droplet in microfluidic system. Anal Chim Acta 2006. [DOI: 10.1016/j.aca.2005.10.086] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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41
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Li W, Fries D, Malik A. Negatively charged sol-gel column with stable electroosmotic flow for online preconcentration of zwitterionic biomolecules in capillary electromigration separations. J Sep Sci 2005; 28:2153-64. [PMID: 16318212 DOI: 10.1002/jssc.200500172] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A negatively charged sol-gel coating was developed for on-line preconcentration of zwitterionic biomolecules in capillary electrophoresis (CE), using asparagine and myoglobin as representative zwitterionic bioanalytes. The sol-gel coating was created by using a solution containing three precursors: mercaptopropyltrimethoxysilane (MPTMS), tetramethoxysilane (TMOS), and n-octadecyltriethoxysilane (C18-TEOS). The resulting sol-gel coating contained chemically bonded mercaptopropyl functional groups that were further oxidized by hydrogen peroxide to the corresponding sulfonic acid moieties. Such a surface-bonded sol-gel coating can carry a negative charge over a wide range of pH due to the presence of deprotonated sulfonic acid groups. Under favorable pH conditions, the negatively charged sol-gel coating can facilitate the extraction of positively charged analytes from a zwitterionic sample through electrostatic interaction. This principle was employed to extract myoglobin and asparagine by passing aqueous samples of these zwitterionic analytes through a negatively charged sol-gel column. The extracted analytes were then desorbed and focused via local pH change and stacking. The local pH change was accomplished by passing a buffer solution with a pH above the solute p/ value, while a dynamic pH junction between the sample solution and the background electrolyte was utilized to facilitate solute focusing. The sorption/desorption phenomena could, perhaps, also be explained on the basis of ion-exchange and local pH junction effects. On-line preconcentration and analysis results obtained on sulfonated sol-gel columns were compared with those obtained on an uncoated fused silica capillary of identical dimensions using conventional sample injections. Using UV detection, the presented sample preconcentration technique provided a sensitivity enhancement factor (SEF) on the order of 3 x 10(3) for myoglobin, and 7 x 10(3) for asparagine.
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Affiliation(s)
- Wen Li
- Department of Chemistry, University of South Florida, Tampa, FL 33620, USA
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42
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Liu Y, Foote RS, Jacobson SC, Ramsey JM. Stacking due to ionic transport number mismatch during sample sweeping on microchips. LAB ON A CHIP 2005; 5:457-465. [PMID: 15791345 DOI: 10.1039/b416414h] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Sample stacking can occur in isoconductive buffer systems as a result of ion transport mismatches that cause changes in buffer conductivity during electrophoresis. Fluorescence imaging was used to examine this effect in the sweeping of hydrophobic dyes with sodium dodecyl sulfate (SDS) on microchips. Imaging revealed the occurrence of a stacking effect in a sodium borate buffer system in which the sample buffer and SDS-containing run buffer had the same initial conductivity. Injected sample plugs were first swept by SDS micelles and the swept band was then stacked at the trailing end of the sample zone. This effect is due to changes in conductivity at both the front and back interfaces of the injected sample plug and can be modeled by moving boundary equations. Maximum signal enhancements of 86-, 160- and 560-fold were obtained for Rhodamine 560, Rhodamine B and Rhodamine 6G, respectively, by the combination of sweeping and stacking within a 1 cm section of microchannel. Based on sample sweeping/stacking and manipulation of the electric field polarity, a method of trapping and concentrating analyte from multiple injections was also demonstrated.
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Affiliation(s)
- Yingjie Liu
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6142, USA
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43
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Shihabi ZK. Organic solvent high-field amplified stacking for basic compounds in capillary electrophoresis. J Chromatogr A 2005; 1066:205-10. [PMID: 15794572 DOI: 10.1016/j.chroma.2005.01.021] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Many water-miscible organic solvents, especially acetonitrile and acetone, bring along significant degrees (approximately 30 times) of stacking by electroinjection through high-field amplified injection for the basic compounds compared to that for aqueous buffers or water. The relative stacking of different compounds in acetonitrile or acetone is different compared to that for water. Stacking by electroinjection in organic solvents is less stringent and easier to accomplish in practice. Acids and salts, in aqueous solutions, can ruin the stacking for both organic and aqueous solvents; however, this effect can be better tolerated by diluting the sample in acetonitrile. Thus, this stacking is termed "organic solvent high-field amplified injection". This stacking by electroinjection is enhanced by increasing the electrophoresis buffer concentration and can be better than that by pressure injection. From the practical aspects, some cationic drugs present in serum such as amiodarone can be detected at the therapeutic levels by electroinjection on the capillary after protein precipitation by acetonitrile.
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Affiliation(s)
- Zak K Shihabi
- Department of Pathology, Wake Forest University School of Medicine, Baptist Medical Center, Winston-Salem, NC 27157, USA.
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44
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Cao CX, Zhang W, Qin WH, Li S, Zhu W, Liu W. Quantitative Predictions to Conditions of Zwitterionic Stacking by Transient Moving Chemical Reaction Boundary Created with Weak Electrolyte Buffers in Capillary Electrophoresis. Anal Chem 2005; 77:955-63. [PMID: 15858973 DOI: 10.1021/ac049470s] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This paper develops a novel procedure of quantitative predictions for the on-column stacking conditions of a zwitterionic analyte by a moving chemical reaction boundary (MCRB) in capillary electrophoresis (CE). The procedure concerns the choice of the weak acidic running and alkaline sample buffers and the velocity design of MCRB created with the two buffers. Based on the theory of MCRB, the theoretical computations are performed. From the computations, the following two predictions are refined for the stacking conditions of zwitterion. (1) The zwitterion velocity in the acidic buffer should be greater than that of MCRB moving toward the cathode, or the zwitterion cannot be well stacked by the MCRB. (2) The gap between pH values of the acidic and alkaline sample buffers ought to comprise the isoelectric point (pI) of zwitterion to be stacked; namely, there exists the relation of pH (acidic buffer) < pI < pH (sample). The predictions are quantitatively proved by the experiments of zwitterionic stacking with two kinds of MCRBs. In addition, the experiments also show the tightly stacked peak of zwitterion existing in the process of MCRB, but not after the MCRB. The theoretical and experimental results hold obvious significances to other zwitterion (such as peptide and protein) on-column stacking in CE.
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Affiliation(s)
- Cheng-Xi Cao
- Laboratory of Analytical Biochemistry & Bioseparation, School of Life Science and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
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45
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Kitagawa F, Aizawa S, Otsuka K. Rapid Enantioseparation of 1-Aminoindan by Microchip Electrophoresis with Linear-Imaging UV Detection. ANAL SCI 2005; 21:61-5. [PMID: 15675518 DOI: 10.2116/analsci.21.61] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Chiral separations of 1-aminoindan (AI) by cyclodextrin electrokinetic chromatography (CDEKC) were investigated on microfluidic quartz chips. By using a microchip electrophoresis (MCE) instrument equipped with a linear-imaging UV detector, the separation process of the enantiomeric compounds was observed. When sulfated beta-cyclodextrin was employed as a chiral selector, the baseline separation of AI could be achieved within 1 min with a high repeatability. The relative standard deviation of the migration time was less than 6%. The fastest separation was achieved in 14 s, utilizing a separation length of only 6.1 mm. These results show that the MCE analysis employing a linear imaging UV detector has a significant potential for fast chiral analysis.
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Affiliation(s)
- Fumihiko Kitagawa
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
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46
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Fan L, Liu L, Chen H, Chen X, Hu Z. Continuous on-line concentration based on dynamic pH junction for trimethoprim and sulfamethoxazole by microfluidic capillary electrophoresis combined with flow injection analysis system. J Chromatogr A 2005; 1062:133-7. [PMID: 15679151 DOI: 10.1016/j.chroma.2004.11.035] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
A novel, rapid and continuous on-line concentration approach based on dynamic pH junction for the analysis of trimethoprim (TMP) and sulfamethoxazole (SMZ) by microfluidic capillary electrophoresis (CE) combined with flow injection analysis is developed in this paper. Stacking is due to decreases in the velocity of analytes when migrating from the low-pH sample zone (sample was dissolved in 50 mM HCl) to a relatively high-pH buffer (30 mM phosphate buffer, pH 8.5) filled in the capillary. This results in 2.9-4.7-fold improvement in concentration sensitivity relative to conventional capillary electrophoresis methods. The separation could be achieved within 2 min and sample throughput rate can reach up to 38 h(-1).
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Affiliation(s)
- Liuyin Fan
- Department of Chemistry, Lanzhou University, Lanzhou, Gansu Province 730000, PR China
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47
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Kim DK, Kang SH. On-channel base stacking in microchip capillary gel electrophoresis for high-sensitivity DNA fragment analysis. J Chromatogr A 2005; 1064:121-7. [PMID: 15729827 DOI: 10.1016/j.chroma.2004.12.045] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We evaluated a novel strategy for high-sensitivity DNA fragment analysis in a conventional glass double-T microfluidic chip. The microchip allows for a DNA on-channel concentration based on base stacking (BS) with a microchip capillary gel electrophoretic (MCGE) separation step in a poly(vinylpyrrolidone) (PVP) sieving matrix. Depending if low conductivity caused a neutralization reaction between the hydroxide ions and the run buffer component Tris+, the stacking of DNA fragments were processed in the microchip. Compared to a conventional MCGE separation with a normal electrokinetic injection, the peak heights of 50-2650-base pair (bp) DNA fragments on the MCGE-BS separation were increased 3.9-8.0-fold. When we applied the MCGE-BS method to the analysis of a clinical sample of bovine theileria after PCR reaction, the peak height intensity of the amplified 816-bp DNA fragment from the 18S rRNA of T. buffeli was enhanced 7.0-fold compared to that of the normal injection method.
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Affiliation(s)
- Dae-Kwang Kim
- Department of Chemistry, Chonbuk National University, Jeonju 561-756, South Korea
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On-line sample preconcentration techniques in capillary electrophoresis. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/s0166-526x(05)45003-5] [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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Song S, Singh AK, Kirby BJ. Electrophoretic Concentration of Proteins at Laser-Patterned Nanoporous Membranes in Microchips. Anal Chem 2004; 76:4589-92. [PMID: 15283607 DOI: 10.1021/ac0497151] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Laser-patterning of nanoporous membranes at the junction of a cross channel in a microchip is used to integrate protein concentration with an electrokinetic injection scheme. Upon application of voltage, linear electrophoretic concentration of charged proteins is achieved at the membrane surface because buffer ions can easily pass through the membrane while proteins larger than the molecular weight cutoff of the membrane (>5700) are retained. Simple buffer systems can be used, and the concentration results constitute outward evidence that the uniformity of buffer ion concentration is maintained throughout the process. Local and spatially averaged concentration are increased by 4 and 2 orders of magnitude, respectively, upon injection with moderate voltages (70-150 V) and concentration times (100 s). The degree of concentration is limited only by the solubility limit of the proteins. The porous polymer membrane can be used repeatedly as long as care is taken to avoid protein precipitation.
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Affiliation(s)
- Simon Song
- Sandia National Laboratories, Livermore, California 94551, USA
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Palmer JF. High-salt stacking principles and sweeping: comments and contrasts on mechanisms for high-sensitivity analysis in capillary electrophoresis. J Chromatogr A 2004; 1036:95-100. [PMID: 15146909 DOI: 10.1016/j.chroma.2004.02.088] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
High-salt stacking in electrokinetic chromatography (EKC) is defined and contrasted to the sweeping method. A recent paper argued the two methods are identical, where high concentrations of micelle in the sample were intended to mimic the effect of high-salt stacking. However, high micelle concentration in the sample matrix in EKC is analogous to using a high-conductivity sample instead of a low-conductivity sample in field amplified stacking. High-salt stacking does not require a sample free of pseuostationary phase, only a sample with a high-mobility co-ion compared to the separation buffer electrokinetic vector. High-salt stacking uses a discontinuous buffer system and should not be confused with continuous buffer stacking systems such as sweeping.
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Affiliation(s)
- James F Palmer
- Department of Physiology and Biophysics, University of California, Medical Sciences I, C-337, Irvine, CA 92697, USA.
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