生理条件下抗坏血酸对 Zn^(2+)、Cd^(2+)、Hg^(2+) 配合能力的研究

STUDIES ON ASCORBIC ACID AND Zn2+、Cd2+、Hg2+ COMPLEX ABILITY AT BIOLOGICAL CONDITION

在生理条件下（Ｔ＝３７℃，Ｉ＝１．０×１０－２ｍｏｌ／Ｌ），采用ｐＨ电势法，测得抗坏血酸浓度为５．０６×１０－２ｍｏｌ／Ｌ时，加合质子常数为ｌｇＫ１Ｈ＝１０．５２，ｌｇＫ２Ｈ＝４．０２。抗坏血酸与Ｚｎ２＋的配合稳定常数为ｌｇＫ１＝９．１６，ｌｇＫ２＝５．８８；与Ｈｇ２＋的配合稳定常数为ｌｇＫ１＝１０．１２，ｌｇＫ２＝６．９８，结果表明，抗坏血酸可与Ｚｎ２＋、Ｈｇ２＋形成配合物，但与Ｃｄ２＋无配合能力。

The complex ability of the ascorbic and with Zn2+、Cd2+、Hg2+ was studied by pH potentiometry.In the ascorbic acid of 5.06×10-2 mol·L-1 and at biological condition(T=37℃,Ⅰ=1.0×10-2 mol·L-1),the ascorbic acid protonation constants are lgK1H=10.52 and lgK2H=4.02.The complex stability constants of the ascorbic acid with Zn2+are lgK1=9.16,lgK2=5.88,and with Hg2+ are lgK1=10.12,lgK2=6.98.The results showed that the complex stability constants of the ascorbic acid with Zn2+ and Hg2+ can be measured,but the ascorbic acid has no complex ability with Cd2+.