Cadmium ion-selective electrode based on tetrathia-12-crown-4

A new polyvinylchloride membrane sensor for Cd2+ ions based on tetrathia-12-crown-4 as an ionophore was prepared. The sensor exhibits a Nernstian response for cadmium ions over a wide concentration range (4.0×10−7 to 1.0×10−1 M) with a slope of 29±1 mV decade−1. The limit of detection is 1.0×10−7 M (0.01 ppm). It has a fast response time of <10 s and can be used for at least 6 weeks without any divergence in potential. The electrode can be used in the pH range from 2.5 to 8.5. The proposed sensor shows fairly good discriminating ability towards Cd2+ ion in comparison with some alkali, alkaline earth, transition and heavy metal ions. It was successfully applied for the direct determination of Cd2+ in solution and, as an indicator electrode, in potentiometric titration of cadmium ions.