示差脉冲极谱法确定镉(Ⅱ)-甘胺酸体系的配合物稳定常数

DETERMINATION OF STABILITY CONSTANTS OF COORDINATION COMPLEXES BETWEEN CADMIUM(Ⅱ) ION AND GLYCINE BY DIFFERENTIAL PULSE POLAROGRAPHY

在镉离子浓度为5．00×10^-5～2．00×10^-4mol·L^-1、甘氨酸与镉离子浓度比为100～400条件下，应用示差脉冲极谱技术测定不同溶液pH值时镉（Ⅱ）-甘氨酸体系的极谱峰电位和峰电流，依据极谱峰电位随溶液pH和自由金属离子浓度的变化关系曲线，建立合适的金属配合物体系模型。通过求解体系的质量平衡方程及拟合试验配合物形成曲线，用计算机分析程序优化得到MHL、ML、ML2、ML3和ML2（OH）五种金属配合物的稳定常数（1gβ）分别为9．67±0．15，4．35±0．02，7．83±0．03，10．04±0．04和11．48±0．13。

The polarographic peak potential and peak current of coordination complexes formed between Cd（Ⅱ ） and glycine at different pH values of the reaction system, having its Cd（ Ⅱ） ion concentration maintained in the range of 5.00×10^-5～2.00×10^-4mol·L^-1 , and the ratio of concentrations of glycine to Cd（Ⅱ ） ion kept in the range of 100 to 400, were measured by differential pulse polarography. Based on the relationship curve on the variation of peak potentials with the variations of pH of the reaction solution and of the concentration of Cd（ Ⅱ ）-ion （in thems of 1g Cd）, a rational model of the metal ion coordination complex was established. By using the optimum computer program, and by solving the mass equilibrium equation of the reaction system, and by fitting the formation curves of the metal coordination complexes tested, the stability constants （1g β） of the five species of coordination complexes. MHL, ML, ML2, ML3 and ML2（OH） were obtained giving values of 9. 67±0. 15, 4. 35±0. 02, 7. 83 ±0. 03, 10. 04±0. 04 and 11.48±0. 13 respectively.