TRIIODIDE ION-SELECTIVE ELECTRODE BASED ON MANGANESE(III)-TETRAPHENYLPORPHINE

A new sensitive and selective electrode for triiodide ion has been developed. The electrode was constructed by incorporating Mn(III)-tetraphenylporphine into a plasticized poly(vinyl chloride) membrane. The electrode shows super-Nernstian response over the range 10(-5) to 10(-3) M triiodide ion in the pH range of 2 to 9, with an anionic slope of 87 mV/concentration decade. The electrode exhibits high specificity for triiodide ion over other anions (salicylate, benzoate, propionate, perchlorate, iodide, bromide, chloride, fluoride, nitrate and bicarbonate). The electrode has been applied to measure triiodide ion generated from iodine. The results have indicated that iodine can be determined by simple potentiometric measurements. A similar method may be applied to determine oxidizing agents, bromine and hydrogen peroxide, which oxidize iodide ion to iodine.