Liquid membrane electrode for selective determination of thiocyanate

Abstract

A liquid membrane electrode which responds to thiocyanate ions is described. It is based on the use of the nitron-thiocyanate ion-pair complex in nitrobenzene as the electroactive species. The electrode response is near-Nernstian over the concentration range 10^–1-10^–5M thiocyanate. The sensitivity of the electrode is high enough to permit the accurate determination of as little as 0.6 µg ml^–1 of thiocyanate without any significant interference from high levels of many reducing species and most common anions including chloride, bromide and cyanide. The potentiometric selectivity coefficient data show negligible interference from 20 different organic and inorganic anions. The electrode has a fast response time (< 80 s), good slope stability over the pH range 3–7 for a period of at least 2 months and can be used for following the potentiometric titration of the thiocyanate with Ag⁺ and Hg²⁺ ions.