Abstract

A Liquid membrane based electrode containing an electroactive chelating substance selective for cobalt (II) ions

Author(s): Nidhi Rani Gupta, Susheel K.Mittal, Subodh Kumar, S.K.Ashok Kumar

Spectrophotometric and conductometric studies on the binding properties of 1,4,8,11-tetraazacyclotetradecane-5,7-dione (I) toward Co2+and different metal ions have been done. Data revealed the occurrence of 1:1 (ligand/metal ion) complexation with a stability order of Co2+>Cu2+>Pb2+> Ni2+>Ag+. Consequently, (I) was also used as a neutral carrier for the preparation of a novel liquid membrane based electrode selective for Co2+ ions. The electrode revealed a Nernstian slope 31mV/decade over wide concentration range 1.0ï‚´10-6 - 1.0ï‚´10-1Mand detection limit 5.0ï‚´10-7M. It has response time of <10 sec and can be used over a constant pH range of 5.0-8.0. The electrode possesses a fast response time and can be used for at least 4 months without observing any considerable deviation in the response behavior and selectivity. Electrode shows a very good selectivity for Co2+ over a number of alkali, alkaline earth, transition, and heavy metal ions. The proposed electrode was successfully applied as an indicator electrode, in potentiometric titration of Co2+ ionswith ethylene diamine tetra acetic acid (EDTA).