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

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).