Potentiometric determination of neodymium (Ⅲ) ions using tin (Ⅳ) antimonotungstate and zirconium (Ⅳ) antimonotungstate as electro-active materials

摘要

Neodymium (Ⅲ)-selective electrodes have been prepared by using tin (Ⅳ) antimonotungstate (SnSbW) and zirconium (Ⅳ) antimonotungstate (ZrSbW) as electro-active materials and epoxy resin as a binding material. In the case of SnSbW, best performance is exhibited by a membrane having the composition: tin (Ⅳ) antimonotungstate (50%) and epoxy resin (50%). It shows excellent response in the concentration range of 10 4 M to 10 ' M Nd (Ⅲ) ion with a super-Nernstian slope of 40.0 mV/decade. It has a fast response time of 20 seconds and can be used for at least six months without any considerable divergence in potential. In the case of ZrSbW, best performance is exhibited by a membrane having the composition: zirconium (Ⅳ) antimonotungstate (40%) and epoxy resin (60%). It shows excellent response in the concentration range of 10 5M to 10"1 M Nd (Ⅲ) ion with a near-Nernstian slope of 25.0mV/decade. It has a fast response time of 10 seconds and can be used for at least six months without any considerable divergence in potential. Effect of internal solution has been studied and the electrode was successfully used in partially non-aqueous medium, too. Selectivity coefficients have been determined by FIM method, with respect to alkali, alkaline earth, some transition and rare earth metal ions. ZrSbW electrode can be used in the pH range of 2.9-9.9 and SnSbW shows pH range 3.0-9.0. Both the electrodes have been used as indicator electrodes in the potentiometric titration of Nd (Ⅲ) ions against EDTA.