Estimation of chloride in oxidizing media by means of ion-selective electrodes

Chloride concentrations down to the ppm level in a large excess of chlorate or perchlorate can be quantitatively estimated by use of chloride ion-selective electrodes (ISEs). Similarly traces of chloride in chromic acid solutions can be estimated with a heterogeneous silicone-rubber based chloride ISE. However, homogeneous chloride ISEs pose a problem for practical applications, because their response in chromic acid solutions changes with time owing to chemical attack on the membrane surface. In permanganate solutions, both homogeneous and heterogeneous type electrodes can be used for monitoring chloride ions. The Orion electrode, however, was found to show a slightly super-Nernstian response in such solutions. The presence of 10(-3)M iron(III) had no adverse effect on the performance of these electrodes in permanganate solutions.