A new triiodide ion- selective electrode based on charge-transfer complex of iodine with 1, 4, 8, 11-tetraazacyclotetracdecane as membrane carrier was prepared. The best performance of electrode observed with the membrane having the ligand – PVC – NPOE – NaTPB composition 3.0: 33: 66: 0.5 mg which worked well over a wide concentration range 2.8 × 10-6 – 1.4 × 10-1 M with a Nernstian slope of 59.6 ± 0.3 mV per decade and a detection limit of 1.2 × 10-6 M. This electrode showed a response time of 25 s and was used over a period of 2 months. The electrode exhibits an anti-Hofmeister selectivity sequence with a performance for triiodide at pH 1.5 - 10.2. The response mechanism of the electrode was investigated by Uv- Vis spectroscopic technique. The electrode was successfully applied as an indicator electrode in the potentiometric titration of ascorbic acid and hydroquinone in drugs.
