Vanadyl and molybdenyl phthalocyanines as ionophores for salicylate-selective membranes coated on graphite electrodes

Salicylate selective electrodes based on oxo(phthalocyanato)vanadium(IV) [V O(Pc), vanadyl phthalocyanine] and oxo(phthalocyanato)molybdenum(IV) [MoO(P c), molybdenyl phthalocyanine] are described. The electrodes were prepared by incorporating the ionophores into plasticized poly(vinyl chloride) membr anes, which were directly coated on the surface of graphite electrodes. The resulting electrodes demonstrate Nernstian responses over a wide linear ra nge (10(-7)-10(-1) M) salicylate. The electrodes have a fast response time, submicromolar detection limit, and could be used over the pH range of 6-9. The proposed sensors revealed selectivity for salicylate over a number of common inorganic and organic anions. The influence of lipophilic cationic a nd anionic additives on the response properties of the electrodes was inves tigated. Highest sensitivity and the widest linear dynamic range were obser ved for the electrodes in the presence of trioctylmethylammonium chloride a s a lipophilic cationic additive. The electrodes were successfully applied to the determination of salicylate in pharmaceutical preparations.