Thiocyanate-selective electrodes based on nickel and iron phthalocyanines

Thiocyanate-selective electrodes based on nickel and iron phthalocyanines are described. The electrodes were prepared by incorporating the ionophores into plastisized poly(vinyl chloride) membranes, which were directly coated on the surface of graphite electrodes. The resulting electrodes demonstrate near-Nernstian responses over a wide linear range (5 x 10(-7)-0.1 M) thiocyanate. The electrodes have a fast response time, submicromolar detection limits (5 x 10(-7) M thiocyanate) and could be used over a wide pH range of 3-10. The influences of lipophilic cationic and anionic additives on the response properties of the electrodes were investigated. The proposed sensors revealed high selectivity for thiocyanate over a number of common inorganic and organic anions. Highest selectivity was observed for the electrode based on iron phthalocyanine in the presence of sodium tetraphenylborate as a lipophilic anionic additive. Application of the electrodes for determination of thiocyanate in urine samples is reported. (C)1999 Elsevier Science B.V. All rights reserved.