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.
