Ca(Ⅱ)、Mg(Ⅱ)和Zn(Ⅱ)与丙二醇-水混合体系中L-多巴的二元配合物的生成平衡(英文)

Binary Complex Formation Equilibria of Ca(Ⅱ), Mg(Ⅱ) and Zn(Ⅱ) with L-dopa in Propylene Glycol-Water Mixtures

在303 K恒温条件下，以NaCl为电解质保持离子强度为0．16mol·L-1，用pH滴定法研究了M（Ⅱ）-Dopa（多巴）二元配合物在0-60％（V/V）的丙二醇（PG）-水体系中的生成平衡。在PG-水体系中，Ca（Ⅱ）和Mg（Ⅱ）的典型配合物为MLH，ML2，ML2H和ML2H2，而Zn（Ⅱ）的典型配合物为ML，MLH，ML2，ML2H和ML2H2。根据静电和非静电力解释了稳定常数随介质的介电常数而变化的倾向。还讨论了在不同组成的丙二醇（PG）-水体系中配合物物种随pH值变化的情况。

The complex formation equilibria involved in the binary systems of M （Ⅱ）-Dopa in 0-60% （V/V） propylene glycol （PG）-water mixtures were studied using pH-metric titration at constant temperature of 303 K and a constant ionic strength of 0.16 mol.L-1 held by using sodium chloride as an electrolyte. The models contained MLH, ML2, ML2H and MGH2 for Ca（Ⅱ） and Mg（Ⅱ）, but ML, MLH, ML2, ML2H and ML2H2 for Zn（Ⅱ） in PG-water mixtures. The trend in the variation of stability constants with change in the dielectric constant of the medium was explained on the basis of electrostatic and non-electrostatic forces. Distributions of these species with pH value at different compositions of PG-water mixtures were also presented.