Abstract: Europium (III)-selective electrodes have been prepared by using Tin (IV) arsenophosphate (SnAsP) as electroactive material and epoxy resin, PVC, polystyrene as binding materials.  A membrane having composition 60% SnAsP and 40% PVC exhibits best performance. It shows excellent response in the concentration range of 10^-5 M to10^-1 M Eu (III) ion with Nernstian slope of 20 V/decade. It has fast response time of less then 10 sec. Effect of internal solution was studied and the electrode was successfully used in partially non-aqueous medium. The proposed sensor revealed good selectivity with respect to alkali, alkaline earth, some transition and rare earth metal ions and can be used in the pH range of 3.10 - 8.20. It was used as an indicator electrode in the potentiometric titration of Eu (III) ion against EDTA.

Key words: FIM, Inorganic ion exchanger, ISE, Eu, Potentiometric titration, PVC membrane, Ion selective electrode.