title: Quantitative predictions to conditions of zwitterionic stacking by transient moving chemical reaction boundary created with weak electrolyte buffers in capillary electrophoresis.
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.
authors.affiliation: Laboratory of Analytical Biochemistry & Bioseparation, School of Life Science and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China. cxcao@sjtu.edu.cn
authors.forename: Cheng-Xi
authors.initials: CX
authors.lastname: Cao
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Wei-Hua
authors.initials: WH
authors.lastname: Qin
authors.forename: Shan
authors.initials: S
authors.lastname: Li
authors.forename: Wei
authors.initials: W
authors.lastname: Zhu
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
mesh_terms: D002021:Buffers; D004573:Electrolytes; D019075:Electrophoresis, Capillary / Q000379:methods*; D014364:Tryptophan / Q000032:analysis* / Q000737:chemistry
chemical_list: D002021:Buffers; D004573:Electrolytes; D014364:Tryptophan