FLOW-INJECTION POTENTIOMETRIC DETERMINATION OF FREE CADMIUM IONS WITHA CADMIUM ION-SELECTIVE ELECTRODE

The determination of free cadmium ions with solid-state cadmium ion-se lective electrode can be performed in non-flow measurements in non-buf fered solutions in a wide concentration range down to pCd 10. In cadmi um ion buffered solutions linear Nernstian response was obtained even down to pCd 12, which is lower, that expected based on calculation of cadmium solubility from the conditional solubility product. Interferen ces of trace amounts of Fe(III), Cu(II) and Pb(II) commonly present in natural waters in larger concentrations than Cd(II) can be eliminated by reduction with hydroxylamine, complexation with Neocuproine and io n-exchange on anion-exchange resin in sulphate form, respectively. The developed procedure might be suitable for the determination of activi ty of free cadmium ions in natural water. A preliminary study on this subject is demonstrated for river water sample using stopped-flow flow -injection system. (C) 1998 Elsevier Science B.V. All rights reserved.