茜素S选择电极的研制和应用

本文报道了茜素S电极的研制和应用。比较了季铵盐、季鏻盐、碱性染料和邻二氮菲金属配合盐作为活性物质、各种介体溶剂以及活性物质在膜相中的含量对电极性能的影响。以三辛基甲基氯化铵制成的PVC膜型电极对茜素S在2×10~(-4)～5×10~(-7)M浓度范围内呈Nernstian响应,检测下限为2×10~(-7)M。测定了一些阴离子的选择系数,ClO_4~-,CNS~-,I~-以及能与茜素S配合的金属离子有明显干扰。报道了以茜素S电极为指示电极,用EDTA和茜素S为滴定剂滴定钪和稀土的情况。以茜素8电位滴定钪及钴-钐合金中的钐,都获得良好的结果。

Preparation and application of alizarins ion selective electrode.

An acidic dye, alizarin S, PVC-matrix ion selective electrode was prepared by using its salts of large cation as a sensing element. The effects of various quaternary ammonium salts, quaternary phosphonium salts, basic dye, ferroin ion and various mediator solvents have been discussed in detail. Trioctylmentyl ammonium chloride and dibutyl phthalate are preferred. The optimum membrane content of sensing element is 0.12%. The response to alizarin S ion is linear with a Nernstian slope 57 m V/decade over the concentration range of 2X10-4-5X10-7M in the pH range of 2-4.2. The limit of detection is 2X10-7M. The selectivity coefficients of various common anions were determined. ClO4^-, CNS- and I- anions show remarkable interference. As alizarin S is a metallochromic indicator, the variations of potential in the presence of some metals were also tested. The electrode potential drift is less than 2mV for the duration of eight hours period. The stability and reproducibility are satisfactory. The life time of the membrane is more than four months. This electrode can be used as an indicator electrode in the potentiometric titration with EDTA and ARS. It is necessary to titrate Sc at proper pH in order to avoid interference and to get good precision. There is no interference from alkali and alkaline earth metals and the amounts of La as much as 30 times the amounts of Sc and Y 10 times of Sc do not interfere at designated pH. It is a good practice to determine Sc potentiometrically with alizarin S as a titrant. The variation coefficient is 0.4%. The present method is suitable for the determination of Sm in Co-Sm alloys with good results.