A novel thiocyanate-selective electrode based on a zinc–phthalocyanine complex

AbstractA novel thiocyanate (SCN−)-selective PVC membrane electrode based on a zinc-phthalocyanine (ZnPc) complex as neutral carrier is described. The membrane electrode containing ZnPc with 5.1% (w/w) ionophore, 29.2% (w/w) PVC, and 65.7% (w/w) 2-nitrophenyl octyl ether (o-NPOE) as plasticizer displayed an anti-Hofmeister selectivity sequence % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX!% MathType!MTEF!2!1!+-% feaafaart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX% garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz% aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq% Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq% Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaaca% qGOaGaae4uaiaaboeacaqGobWaaWbaaSqabeaacqGHsislaaGccqGH% +aGpcaqGtbGaaeyyaiaabYgadaahaaWcbeqaaiabgkHiTaaakiabg6% da+iaabMeadaahaaWcbeqaaiabgkHiTaaakiabg6da+iaaboeacaqG% SbGaae4tamaaBaaaleaacaqG0aaabeaakmaaCaaaleqabaGaeyOeI0% caaOGaeyOpa4JaaeOqaiaabkhadaahaaWcbeqaaiabgkHiTaaakiab% g6da+iaaboeacaqGSbWaaWbaaSqabeaacqGHsislaaGccqGH+aGpci% GGobGaai4tamaaBaaaleaacaGGZaaabeaakmaaCaaaleqabaGaeyOe% I0caaOGaeyOpa4JaaeOtaiaab+eadaWgaaWcbaGaaeOmaaqabaGcda% ahaaWcbeqaaiabgkHiTaaakiabg6da+iaabIeadaWgaaWcbaGaaeOm% aaqabaGccaqGqbGaae4tamaaBaaaleaacaqG0aaabeaakmaaCaaale% qabaGaeyOeI0caaOGaeyOpa4Jaae4uaiaab+eadaWgaaWcbaGaaein% aaqabaGcdaahaaWcbeqaaiaaikdacqGHsislaaGccaGGPaGaaiilaa% aa!67CA!$${\text{(SCN}}^ - > {\text{Sal}}^ - > {\text{I}}^ - > {\text{ClO}}_{\text{4}} ^ - > {\text{Br}}^ - > {\text{Cl}}^ - > \operatorname{NO} _3 ^ - > {\text{NO}}_{\text{2}} ^ - > {\text{H}}_{\text{2}} {\text{PO}}_{\text{4}} ^ - > {\text{SO}}_{\text{4}} ^{2 - } )$$, and exhibited near-Nernstian potential response to thiocyanate ranging from about 1.0×10−1 to 1.0×10−6 mol L−1 with a detection limit of 7.5×10−7 mol L−1 and a slope of 58.1±0.5 mV per decade in pH 3.0 phosphate buffer solution at 25 °C. This preferential response is believed to be associated with the unique coordination between the central metal of the carrier and thiocyanate.