A new PVC membrane electrode for the triiodide ion based on a charge-transfer complex of iodine with 7,16-dibenzyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane as a membrane carrier was prepared. The electrode exhibits a Nernstian response for triiodide ions over a wide concentration range (1.0 × 10 -1 -1.0 × 10 -5 M) with a slope of 59.3 ± 0.9 mV decade -1 and a detection limit of 6.3 × 10 -6 M. It has a response time of 30 s and can be used for at least 3 months without any divergence in the potential. The potentiometric response is independent of the pH, in the pH range 1.6 -10.0. The proposed electrode has shown very high selectivity for the triiodide ion over a wide variety of other anions. This electrode was successfully applied as an indicator electrode in the potentiometric titration of ascorbic acid and hydroquinone from pharmaceutical preparations as well as ascorbic acid in orange juice and dissolved O2 in tap water.

Two new highly selective triiodide electrodes have been prepared using charge‐transfer complex of iodine with cryptand 222 as an electroactive ionophore and nitrophenyl octyl ether as a plasticizing agent. The electrodes showed Nernstian response to triiodide ions over a concentration range from 1.0 × 10−;2 — 7.9 × 10−;7 M and from 1.0 × 10−;2 — 1 × 10−;6 M with detection limits of 6.3 × 10−;7 and 7.9 × 10−;7 M for cryptand and its charge‐transfer complex with iodine, respectively. The response times (t95%) of the sensors were 10 and 5 s. The membrane could be used for more than 1 month without any divergence in potentials. The proposed sensors exhibited very high selectivity for triiodide ion over other anions, and could be used in a wide pH range ˜2–10. These electrodes were successfully applied as an indicator electrode in potentiometric titration of copper in ore samples.