离子缔合型的指示剂电极,已有铬天青S、茜素S、铬黑T等多种,但尚未见邻苯二酚紫电极的报导。邻苯二酚紫作为络合滴定的目视指示剂,由于终点不够明显,近年来使用较少。本文报导一种PVC膜邻苯二酚紫电极,可作指示电极用于以EDTA滴定一些金属离子。 1.活性膜成分的选择:以三种季铵盐以及乙基紫为活性材料制成电极。增塑剂皆为邻苯二甲酸二丁酯。结果见表1的前四行。由于邻苯二酚紫阴离子的亲脂性不强,由这四种活性材料制成的电极性能相差较大,其中以四(十二烷基)铵制成电极的线性下限最低,但斜率不高;乙基紫制成电极的斜率较高,在低浓度时甚至有超Nernst响应,但线性范围不宽, Ion-associated indicator electrode, there are chrome azure S, alizarin S, chrome black T and so on, but has not been reported catechol purple electrode. Catechol violet as a visual indicator of complexometric titration, the end point is not obvious enough, less used in recent years. This paper reports a PVC membrane catechol violet electrode, which can be used as an indicator electrode for EDTA titration of some metal ions. 1. The choice of active membrane components: three quaternary ammonium salt and ethyl violet as the active material electrode. Plasticizers are all dibutyl phthalate. The results are shown in the first four lines of Table 1. Due to the lack of lipophilicity of catechol violet anions, the electrodes made from these four active materials differ greatly in their performance. Among them, the electrode with tetrakis (dodecyl) ammonium has the lowest linear lower limit, but the slope is not high ; Ethyl violet made of high slope electrode, even at low concentrations and even super-Nernst response, but the linear range is not wide,