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Naydenov CL, Kirazov EP, Mitev VI. Generalized Physicochemical Model for the Natural pH Gradient in Classic IEF. Chromatographia 2014. [DOI: 10.1007/s10337-014-2644-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Online sample pre-concentration via dynamic pH junction in capillary and microchip electrophoresis. J Sep Sci 2011; 34:2800-21. [DOI: 10.1002/jssc.201100414] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Liang H, OuYang LF, Liu Q, Zhang L, Tian LJ, Chen Y. Time-varying migration process of moving neutralization boundary on the immobilized pH gradient strip in the weak-base rehydration buffer. J Sep Sci 2011; 34:1212-9. [DOI: 10.1002/jssc.201000813] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Revised: 02/08/2011] [Accepted: 02/25/2011] [Indexed: 11/05/2022]
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Anouti S, Vandenabeele-Trambouze O, Cottet H. Heart-cutting 2D-CE with on-line preconcentration for the chiral analysis of native amino acids. Electrophoresis 2010; 31:1029-35. [DOI: 10.1002/elps.200900639] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Naydenov CL, Kirazov EP, Lozanov VS, Kirazov LP, Mitev VI. Electrochemical Reactions During Isoelectric Focusing and Their Role in Establishment of the pH Gradient. Chromatographia 2009. [DOI: 10.1365/s10337-008-0949-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Fan L, Li C, Zhang W, Cao C, Zhou P, Deng Z. Quantitative investigations on moving chelation boundary within a continuous EDTA-based sample sweeping system in capillary electrophoresis. Electrophoresis 2008; 29:3989-98. [DOI: 10.1002/elps.200800051] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Cao CX, Fan LY, Zhang W. Review on the theory of moving reaction boundary, electromigration reaction methods and applications in isoelectric focusing and sample pre-concentration. Analyst 2008; 133:1139-57. [DOI: 10.1039/b807450j] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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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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Li M, Fan LY, Zhang W, Cao CX. Stacking and quantitative analysis of lovastatin in urine samples by the transient moving chemical reaction boundary method in capillary electrophoresis. Anal Bioanal Chem 2007; 387:2719-25. [PMID: 17333149 DOI: 10.1007/s00216-007-1169-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2006] [Revised: 01/29/2007] [Accepted: 01/31/2007] [Indexed: 11/24/2022]
Abstract
A simple, sensitive, and useful concentration method for lovastatin (Lvt) in urine has been developed based on the transient moving chemical reaction boundary method (tMCRBM) in capillary electrophoresis. The MCRB is formed with acidic sample buffer (Gly-HCl) and alkaline running buffer (Gly-NaOH). The following optimal conditions were determined for stacking and separation: electrophoretic buffer of 100 mM Gly- NaOH (pH 11.52), sample buffer of 20 mM Gly-HCl (pH 4.93), fused-silica capillary of 76 cm x 75-microm i.d (67 cm from detector), sample injection at 14 mbar for 3 min. A 21- to 26-fold increase in peak height was achieved for detection of Lvt in urine under the optimal conditions compared with normal capillary zone electrophoresis. By combining the sample pretreatment procedure with the stacking method, the sensitivity of Lvt in urine was increased by 105- to 130-fold. The limits of detection (LOD) and quantification (LOQ) for Lvt in urine were decreased to 8.8 ng/mL and 29.2 ng/mL, respectively. The intra-day and inter-day precision values (expressed as RSD) were 2.23-3.61% and 4.03-5.05%, respectively. The recoveries of the analyte at three concentration levels changed from 82.65 to 100.49%.
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Affiliation(s)
- Min Li
- Laboratory of Analytical Biochemistry and Bioseparation, School of Life Science and Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Minhang, 200240 Shanghai, China
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Wang QL, Fan LY, Zhang W, Cao CX. Sensitive analysis of two barbiturates in human urine by capillary electrophoresis with sample stacking induced by moving reaction boundary. Anal Chim Acta 2006; 580:200-5. [PMID: 17723774 DOI: 10.1016/j.aca.2006.07.073] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2006] [Revised: 07/26/2006] [Accepted: 07/27/2006] [Indexed: 02/05/2023]
Abstract
An on-line stacking method based on moving reaction boundary (MRB) was developed for the sensitive determination of barbital and phenobarbital in human urine via capillary electrophoresis (CE). The optimized conditions for the method are: 60 mmol L(-1) pH 11.0 Gly-NaOH as the background electrolyte, 10 mmol L(-1) pH 5.5 Gly-HCl as sample buffer, secobarbital as the internal standard (IS), 12.5 kV, 1.4 psi 10s sample injection, 75 microm ID 60.2 cm total length (50 cm effective length) capillary and 214 nm detect wavelength. Under the optimized conditions, the method can well stack and separate barbital and phenobarbital in urine samples and result in 20.5-fold and 22.6-fold improvement in concentration sensitivity for barbital and phenobarbital, respectively. Furthermore, the method holds: (1) good linear calibration functions for the two target compounds (correlation coefficients r>0.999), (2) low limits of detection (0.27 microg mL(-1) for barbital and 0.26 microg mL(-1) for phenobarbital), (3) low limits of quantification (0.92 microg mL(-1) for barbital and 0.87 microg mL(-1) for phenobarbital), (4) good precision (R.S.D. of intra-day and inter-day less than 5.38% for barbital and 1.67% for phenobarbital, respectively) and (5) high recoveries at three concentration levels (90.27-106.36% for barbital and 93.05-113.60% for phenobarbital in urine). The method is simple, sensitive and efficient, and can fit to the need of clinical and forensic toxicology.
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Affiliation(s)
- Qiu-Ling Wang
- Laboratory of Analytical Biochemistry & Bioseparation, School of Life Science & Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
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Qin WH, Cao CX, Li S, Zhang W, Liu W. Quantitative study on selective stacking of zwitterions in large-volume sample matrix by moving reaction boundary in capillary electrophoresis. Electrophoresis 2005; 26:3113-24. [PMID: 16041697 DOI: 10.1002/elps.200400010] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The paper advanced the theoretical procedures for quantitative design on selective stacking of zwitterions in full capillary sample matrix by a cathodic-direction moving reaction boundary (MRB) in capillary electrophoresis (CE) under control of electroosmotic flow (EOF). With the procedures, we conducted the theoretical computations on the selective stacking of two test analytes of L-histidine (His) and L-tryptophan (Trp) by the MRB created with 30 mM pH 3.0 formic acid-NaOH buffer and 2-80 mM sodium formate. The results revealed the following three predictions. At first, the MRB cannot stack His and Trp plugs if less than 12.5 mM sodium formate is used to form the MRB and prepare the sample matrix. Second, the MRB can stack His and/or Trp sample plugs completely if higher than 50 mM sodium formate is chosen to form the MRB. Third, the MRB can only focus His plug completely, but stack Trp plug partially if 20-50 mM sodium formate is used; this implied the complete MRB-induced selective stacking to His rather than Trp. All the three predictions were quantitatively proved by the experiments. With great dilution of sample matrix and control of EOF, controllable, simultaneous and MRB-induced selective stacking and separation of zwitterions were achieved. The theoretical results hold evident significances to the quantitative design of selective stacking conditions and the increase of detection sensitivity of zwitterions in CE. In addition, the control of EOF by cetyltrimethylammonium bromide (CTAB) can evidently improve the stacking efficiency to both His and Trp.
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Affiliation(s)
- Wei-Hua Qin
- Laboratory of Analytical Biochemistry & Bioseparation, School of Life Science and Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Minhang, 200240 Shanghai, China
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Gillogly JA, Lunte CE. pH-mediated acid stacking with reverse pressure for the analysis of cationic pharmaceuticals in capillary electrophoresis. Electrophoresis 2005; 26:633-9. [PMID: 15690436 PMCID: PMC2519829 DOI: 10.1002/elps.200410061] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
When using capillary electrophoresis (CE) for the analysis of biological samples, it is often necessary to employ techniques to overcome peak-broadening that results from having a high-conductivity sample matrix. To improve the concentration detection limits and separation efficiency of cationic pharmaceuticals in CE, pH-mediated acid stacking was performed to electrofocus the sample, improving separation sensitivity for the analyzed cations by 60-fold. However, this method introduces a large titrated acid plug into the capillary. To overcome the limitations this low-conductivity plug poses to stacking, the plug was removed prior to the separation step by applying reverse pressure to force it out of the anode of the capillary. Employing this technique allows for roughly twice the volume of sample to be injected. A maximum sample injection time of 240 s was attainable with baseline peak resolution compared to a maximum sample injection time of 120 s without reverse pressure, leading to a twofold decrease in the limits of detection of the analytes used. Separation efficiency overall is also improved when utilizing the reverse pressure step. For example, a 60 s sample injection time results in 94,000 theoretical plates as compared to 60,500 theoretical plates without reverse pressure. This reverse-pressure method was used for detection and quantitation of several cationic pharmaceuticals that were prepared in Ringer's solution to simulate microdialysis sampling conditions.
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Affiliation(s)
- Julie A Gillogly
- Department of Chemistry, The University of Kansas, Lawrence, KS 66045, USA
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Li S, Cao CX, Lin ZX, Luo JF. Theoretical study on colloid/or inorganic material preparation by moving reaction boundary method in gel. Colloid Polym Sci 2005. [DOI: 10.1007/s00396-004-1263-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Cao CX, He YZ, Li M, Qian YT, Yang L, Qu QS, Zhou SL, Chen WK. Improving separation efficiency of capillary zone electrophoresis of tryptophan and phenylalanine with the transient moving chemical reaction boundary method. J Chromatogr A 2002; 952:39-46. [PMID: 12064544 DOI: 10.1016/s0021-9673(02)00065-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
A simple and convenient mode--moving chemical reaction boundary method-capillary zone electrophoresis (MCRBM-CZE)--was designed for the enhancement of separating efficiency of CZE. In this mode, the transient MCRBM is used for the on-line pre-treatment of sample. By analyses of tryptophan (Trp) and phenylalanine (Phe) as an example, the experiments by MCRBM-CZE were carried out and further compared with those by normal CZE without the transient MCRBM. The results reveal that by carefully selected appropriate electrolytes, a strong condensation effect can be achieved by using MCRBM-CZE; this effect can greatly improve the separation efficiency, resolution and peak height of Trp and Phe in CZE as compared with those of normal CZE of Trp and Phe. Even if the sample comprises high concentrations of salt, such as 80 mM NaCl (concentration of sodium ion up to 145.6 mM), the same condensation effect can also been observed; this implies obvious significance for biological samples like urine and serum. However, if the electrolytes was chosen inappropriately only a poor compression effect of sample was observed in the MCRBM-CZE runs.
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Affiliation(s)
- Cheng-Xi Cao
- College of Life Science and Biotechnology, Shanghai Jiaotong University, China.
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Cao CX, Zhou SL, Qian YA, He YZ, Yang L, Qu QS, Chen WK. Experimental investigation on moving chemical reaction boundary theory for weak-acid-strong-base system with background electrolyte KCl in large concentration. J Chromatogr A 2001; 922:283-92. [PMID: 11486874 DOI: 10.1016/s0021-9673(01)00847-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In this report, the moving chemical reaction boundary (MCRB) was formed with the weak acid of acetic acid (HAc) and the strong alkali of NaOH, coupled with the excess of background electrolyte KCl. The experiments were compared with the predictions by the moving chemical reaction boundary equation (MCRBE). It is very interesting that (1) the experimental results are in good agreement with the predictions with the original MCRBE if the MCRB is an anodic moving boundary, (2) however, the experiments are extremely far away from the predictions with the original MCRBE if a cathodic moving boundary. Hence, the original MCRBE must be corrected under the later situation of cathodic moving MCRB. The corrected MCRBE was well quantitatively proved to be valid for the cathodic moving MNRB formed with the same electrolytes of HAc, NaOH and KCl.
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Affiliation(s)
- C X Cao
- Department of Chemistry, University of Science and Technology of China, Hefei.
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