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Quantitative Predictions to Conditions of
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提 供 商：
北京彩陆科学仪器有限公司
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资料大小：
132K
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发布时间：
2006-06-27
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浏览次数：
1833
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资料介绍
This paper develops a novel procedure of quantitativepredictions 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 onditions 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.
Anal. Chem.2005, 77,955-963
Articles
Quantitative Predictions to Conditions of
Zwitterionic Stacking by Transient Moving
Chemical Reaction Boundary Created with Weak
Electrolyte Buffers in Capillary Electrophoresis
Cheng-Xi Cao,*,†,‡ Wei Zhang,† Wei-Hua Qin,† Shan Li,† Wei Zhu,† and Wei Liu‡
Laboratory of Analytical Biochemistry & Bioseparation, School of Life Science and Biotechnology,
Shanghai Jiao Tong University, Shanghai 200240, China, and Department of Chemistry,
University of Science and Technology of China, Hefei 230026, China
This paper develops a novel procedure of quantitativepredictions 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 onditions 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.
On-column stacking, viz., preconcentration, of analytes in a sample matrix has become a simple, convenient, and economical but very powerful tool used to greatly improve the detection sensitivity of capillary electrophoresis (CE). In 1988-1992, Bocˇek et al.1,2 developed the preconcentration of transient isotachophoresis (tITP) in CE and Jandik and Jones3 achieved over 100-fold sensitivity increase by tITP. Almost at the same time, Chien and Burgi4-8 created the field amplification sample injection (FASI) and really concentrated analytes up to 1000-fold in CE. In 1998, Quirino and Terabe9 successfully enhanced the sensitivity of micellar electrokinetic chromatography over 5000-fold. Recently, Yang et al.10 enhanced the sensitivity of CE 7000-fold with FASI coupled with nonuniform electrical field, and Zhang et al.11decreased the detection limit of CE greater than 10 000-fold with a pure FASI technique. Significantly, Quirino and Terabe12 improved the sensitivity of CE up to a millionfold with FASI joined with sweeping method.Importantly, numerous methods of preconcentration for analytes were successfully developed during the past decade. The tITP1,2,12 and FASI 4-8,10,11 that were developed during the early stage of 1990s were mentioned above. The following will further supply a few of notable cases. From 1998 to 2002, Quirino et al.9,13-15 and Palmer et al.16-18 pictured a novel sweeping procedure for the stacking of neutral and charged analytes by the interaction between micellar molecular and analytes. During the period 2000-2003, Britz-McKibbin, Chen et al.19-21 invented the pH junction stacking for the reconcentration of analytes in a sample matrix. In 1996-2003, Lunte’s group22-25 advanced the pHmediated stacking method for analyses of drugs in a biological sample matrix. In 2002, Shihabi26,27 added many kinds of watermiscible organic solvents (such as acetonitrile, acetone, and alcohols) into salt sample matrixes. The water-miscible organic solvents can induce a FASI mechanism by decreasing the ionization of salt in the sample matrix,<
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