Highly selective thiocyanate poly(vinyl chloride) membrane electrode based on a cadmium-Schiff's base complex

A PVC membrane electrode based on a cadmium-salen (N,N'-bis-salicylidene-1,2-ethylenediamine) complex as an anion carrier is described. The electrode has an anti-Hofmeister selectivity sequence with a preference for thiocyanate at pH 1.5-11.0. It has a linear response to thiocyanate from 1.0 x 10(-6) to 1.0 x 10(-1) mol L(-1) with a slope of 59.1 +/- 0.2 mV per decade, and a detection limit of 7 x 10(-7) mol L(-1). This electrode has high selectivity for thiocyanate relative to many common organic and inorganic anions. The proposed sensor has a fast response time of approximately 15 s. It was applied to the determination of thiocyanate in a milk sample.