Iodide Selective Electrode Based on Cobalt (II) Complex with Unsymmetrical Schiff Base as Neutral Carrier

A new highly selective poly vinyl chloride membrane iodide electrode of cobalt( U) complex with unsymmetncal schiff base as neutrual carrier was studied, which was based on the fact that ethylenediamine reacts with acetylaetone and salicylaldehyde. It displays a preferential potertiometric response to iodide and an anti-Hofmeister selectivity sequence in following order: I- > Sal(-) > SCN- > ClO4- > SO32- > Br- > NO2- > Cl- > Ac- > NO3- > SO42-. The electrode exhibited near Nernstian potential response to iodide with a linear range from 1.0 x 10(-7) to 1.0 x 10(-1) mol/L, a detection limit of 3.9 x 10(-8) mol/L and a slope of -50.7 mV/dec in pH 2.0 of phosphorate bufer solution at 26 degrees C. The response mechanism was discussed in view of the a. c. impedance technique and the UV spectroscopy. It is shown that the anti-Hofmeister behavior of the electrode results from the direct interaction between the central metal ion and the analyte ion and sterie efect associated with the structure of the carrier. The electrode has the advantages of simplicity, fast response, fair stability, reproducibility and low detection limit. The electrode has been successfully applied to the detemination of iodide in pharmaceuticals and salts with satisfactory results.