双层夹心膜电极电位法测定溶剂聚合物膜中杯芳烃-金属离子配合物的生成常数

以双层夹心膜电极为指示电极,采用电位法测定了聚合物膜中活性离子载体杯6]芳烃乙酯与金属离子形成的配合物的生成常数.提出了一种新的测定夹心膜膜电位的方法,由测得的膜电位可计算出配合物的生成常数.以杯6]芳烃乙酯为离子载体,测得其与Li⁺,Na⁺,K⁺,Cs⁺和NH⁺₄等离子的配合物生成常数的对数值分别为6.14,6.48.6.74,7.43和6.21.制备了以Cs⁺为主离子的选择性电极,采用固定干扰法,测得对Li⁺,Na⁺,K⁺和NH⁺₄等离子的选择性系数的对数值分别为-3.33,-2.54,-1.6和-2.9.实验结果表明,配合物的生成常数与选择性系数之间有较好的相关性.生成常数越大,电极对相应离子的选择性越高.

Potentiometric Determination of Formation Constants of Complex of Calix[6]arene Ester with Metal Ions in Solvent Polymeric Membrane with Two-layer Sandwich Membrane Electrode

A two-layer sandwich membrane was used as the indicator electrode to determine the formation constants of the complexes of tert-butyl-calix6]arene hexaacetic acid hexaethyl ester with metal ions in solvent polymeric membrane potentiometrically. A new method for the measurement of sandwich membrane potential from which the formation constant of the complex can be calculated was proposed. Calix6]arene ester was used as ionophore and the complex formation constants of it with Li+, Na+, K+, Cs+ and NH4+ were determined. The logarithmic values of the formation constants were found to be 6. 14, 6. 48, 6. 74, 7. 43 and 6. 21 respectively. According to the experimental data, Cs+ was chosen as the primary ion because of its highest value of complex formation constant and a Cs-selective electrode was prepared. The resulting logarithmic selectivity coefficients to the ions of Li+, Na+, K+ and NH4+ are found to be -3. 33, -2. 54, -1. 60 and - 2. 90 respectively by fixing interference method (FIM). From the data of both formation constants and selectivity coefficients, a good correlation between them was found. The higher the formation constant of the complex of calix6]arene ester with the responded ion is, the higher the selectivity to it is.