Construction of Triiodide Ion Selective Electrodes Based on Phenothiazine Derivatives

Abstract Novel membrane sensors for triiodide consisting of triiodide‐fluphenazine (FP) and triiodide‐trifluoperazine (TFP) ion pair complexes dispersed in PVC matrix plasticized with 2‐nitrophenyl octal ether with unique selectivity toward I3 − ions are described. The influence of the membrane composition, pH of the test solutions, and foreign ions on the electrode performance were investigated. The optimized membranes demonstrate Nernstian response for triiodide ions over a wide linear range from 1.0 × 10−2 to 5.0 × 10−6 M at 25°C. The electrodes could be used over a wide pH range 2–9, and have the advantages of easy to prepare, good selectivity, fast response time, long lifetime (over 3 months), and small interferences from hydrogen ion. They were successfully used as indicator electrode in the potentiometric titration of triiodide ions and ascorbic acid.