PVC-matrix membrane ion-selective sensors for gold determination in cyanide solutions

Potentiometric sensors with conventional plasticized poly(vinyl-chloride) membranes, sensitive to the dicyanoaurate ion, and two kinds of transducers (an encapsulated pH-sensitive ion-selective field-effect transistor (ISFET) with Ta2O5 as a gate insulator and a silver coated ceramic substrate (AgCer)), were studied. The application of an intermediate hydrophobic polymer layer between the ion sensitive membrane and the transducer surface leads to a dramatical rise of the ISFET life time and, on the contrary, to a decrease of AgCer based sensor durability from 6 months down to 5–6 weeks. The effects of membrane plasticizer and thickness on the performance, selectivity and durability of these sensors were studied.