Triiodide ion is a sufficiently good oxidizing agent to react quantitatively with a number of reductants. It has several application in industry, pharmacology and environmental pollution, such as determination if iron, copper and antimony in ore samples. Therefore a sensitive method is required for its reliable measurements. A new PVC membrane electrode for triiodide ion based on a charge-transfer complex of iodine with (t-but)2DC18C6 as membrane carrier was prepared. The electrode exhibits a nernstien response for triiodide ions over a wide concentration range (6.3×10-2-5×10-6 M ) with a slope of 61+0.99 mV decade-1 and a limit of detection 1.2×10-6 M. It has a response time of 45 s and can be used for at least 2 months without any divergence in potencial. The membrane could be used for two months without any divergence in potentials. The potentiometric response is independent of the pH (at pH rang 1.9-10). The response mechanism of the electrode was investigated by Uv-Vis spectroscopic technique. The proposed electrode showed very high selectivity for triiodide ion over a wide variety of other anions. This electrode was successfully applied as an indicator electrode in potentiometric titration of ascorbic acid in orange juice as well as for the antimony in ore sample with triiodide.
