Triiodide PVC Membrane Electrodes Based on Charge-Transfer Complexes

Three new electrodes were prepared by incorporating two different charge-transfer complexes and amino crown ether into plasticized PVC membranes. The electrodes showed Nernstian response to triiodide ion over the activity range from 1.0 × 10-5 to 1.0 × 10-1 mol·L-1 with detection limits at ∼1.0 × 10- 6 mol·L-1. The resulting electrodes have fast response times (20−30 s) and good stabilities (4 months) and can be used over a wide pH range of 2.5−9.0. The proposed electrodes exhibit anti-Hofmeister behavior with excellent selectivity toward triiodide ion against a wide range of common interferences. Comparative study suggests that amino (aza) crown ether alone or in the form of a charge-transfer complex with iodine, as an ionophore in a PVC liquid membrane, is sensitive to triiodide ion. The electrodes were used as indicator electrodes in potentiometric titration of triiodide ion against thiosulfate ion.