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

A new polyvinylchloride membrane sensor for Cd(2+) 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 x 10(-7) to 1.0 x 10(-1) M) with a slope of 29+/-1 mV decade(-1). The limit of detection is 1.0 x 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 Cd(2+) ion in comparison with some alkali, alkaline earth, transition and heavy metal ions. It was successfully applied for the direct determination of Cd(2+) in solution and, as an indicator electrode, in potentiometric titration of cadmium ions.