用季铵盐定域体制备高碘酸根离子电极的研究

PERIODATE ION ELECTRODE BASED ON QUATERNARY AMMONIUM SITES

实验比较了若干种长链季铵盐制备高碘酸根离子电极,以十六烷基三辛基高碘酸季铵盐(HTOA-IO4)制备的PVC膜电极性能较佳,能斯特响应区间为1.0×10^(-1)—6.3×10^(-8)M,检测下限1.0×10^(-8)M,工作pH范围2.5—7.5,高碘酸在溶液中存在复杂平衡,依据pH-电位曲线,认为电极响应的Ⅰ(ⅥI)离子的主要形态为10^(-4),据此用电位法测试了H5IO6的酸离解常数:K1=5.70×10^(-4),K2=1.97×10^(-7),与文献值相符,测试了不同离子的电位选择性系数。

A number of long-chain quaternary ammonium sites have been compared as the positively charged sites for construction of periodate ion electrodes,among them PVC electrodes based on hexadecyltrioctylam-monium periodate showed best performance characteristics.The Nerstian response range of the electrode is from 1×10^(-1)down to 6.3×10^(-8)M with an optimal working pH 2.5-7,5 and a detection limit of 1×10^(-8)M.In a periodate solution there exist a rather complicated equilibrium of various species of I(Ⅶ).On the basis of analysis of the pH-EMF graph(Fig.2)it has been postulated that among various I(Ⅶ)species IO4-is the primary ion form that the electrode responses to.The acid dissociation constants K1 and K2 of H5IO6 have been determined potentiometrically using this postulate,the values found(K1=5.7×10^(-4);K2=1.97×10^(-7))being in good agreement with those reported in literature.The poten-tiometric selectivity coefficients of various co-existing ions have been determined.