Dissociation kinetics and complexation equilibrium studies of a Zn II complex with l,5-bis(2-hydroxy-5-sulfophenyl)-3-cyanoformazan during capillary electrophoretic separation process

Toru Takahashi, Yuka Takehara, Hitoshi Hoshino

研究成果: Article査読

5 被引用数 (Scopus)

抄録

The dissociation kinetics and the complexation equilibrium of a Zn II complex with 1,5-bis(2-hydroxy-5-sulfophen-yl)-3-cyanoformazan (hscf: H5L) during capillary electrophoretic (CE) separation process were studied. The solvolytic dissociation reaction rate constants of the Zn II-hscf complex ([ZnL]3-) (kd) in the pH range of 6.4 to 8.0 were determined with a CE-based dissociation kinetic analysis method. Small kd values on the order of 10-5s-1 showed the remarkable kinetic inertness of [ZnL]3-, which was detectable in the CE system. The stability constant of [ZnL]3- (KZnL) at 293 K and I = 0.10 was estimated to be [ZnL 3-]/{[Zn2+][L5-]} = 1o 24.2±0.3 through the spectrophotornetric titration. The thermodynamic stability of [ZnL]3- in the pre-capillary complexation stage was thus demonstrated. In contrast, it was shown that the CE separation environment is thermodynamically unsuitable for the metal complexes based on the conditional stability constant of [ZnL]3-, which was determined under CE separation conditions, and the concentration of free HSCF in the complex band in the capillary. Thus, the "stability" of metal complex in the CE system strongly depends on kinetic inertness rather than thermodynamic stability, though their thermodynamic stability is necessary for the pre-capillary derivatization step.

本文言語English
ページ(範囲)910-915
ページ数6
ジャーナルBulletin of the Chemical Society of Japan
80
5
DOI
出版ステータスPublished - 2007 12 1

ASJC Scopus subject areas

  • 化学 (全般)

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