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

A new sensitive and selective electrode for triiodide ion has been dev eloped. The electrode was constructed by incorporating Mn(III)-tetraph enylporphine into a plasticized poly(vinyl chloride) membrane. The ele ctrode 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, per chlorate, iodide, bromide, chloride, fluoride, nitrate and bicarbonate ). The electrode has been applied to measure triiodide ion generated f rom iodine. The results have indicated that iodine can be determined b y simple potentiometric measurements. A similar method may be applied to determine oxidizing agents, bromine and hydrogen peroxide, which ox idize iodide ion to iodine.