SYNTHESIS OF A CHARGE TRANSFER COMPLEX OF (1,3-DIPHENYLDIHYDRO-1H-IMIDAZOLE)-4,S-DIONE DIOXIDE WITH IODIDE AND ITS APPLICATION TO THE DEVELOPMENT OF A HIGHLY SELECTIVE AND SENSITIVE TRIIODIDE PVC-MEMBRANE ELECTRODE

摘要

In this paper a novel membrane triiodide sensor based on a chargetransfer complex of (1,3-diphe-nyldihydro-lH-imidazole)-4, 5-dionedioxime with iodine (CTCI) as a membrane carrier is introduced. The best performance was obtained with a membrane containing 30% polyvinylchloride (PVC), 63% dibutylphta-late (DBP), 5% CTCI and 2% hexadecyltrimethylamrnonium bromide (HTAB). The electrode shows a Nerns-tian behavior (slope of 58.2 ± 0.3) over a very wide triiodide ion concentration range (5.0 x 10~8-1.0 X 10~2 M), and has a low detection limit (4.0 X 10~8 M). The potentiometric response of the sensor is independent of pH of the solution in the pH range of 3.0-9.0. The proposed sensor has a very low response time (<12 s), and also a good selectivity relative to a wide variety of common inorganic and organic anions, including iodide, bromide, chloride, nitrate, sull'ate, thiocyanate, monohydrogen phosphate and acetate. In fact, the selectivity behavior of the proposed triiodide ion-selective electrode shows great improvements compared to the previously reported electrodes for triiodide ion. The proposed membrane sensor can be used for at least 6 months without any divergence in its potentials. The electrode was successfully applied as an indicator electrode in the titration of triiodide with thiosulfate ion.