Tetrachlorophenylporphyrinato manganese(III) acetate as a new ionophore for a coated triiodide ion-selective electrode

A novel triiodide sensor based on (tetrachlorophenylporphyrinato) manganese(III) acetate is described. The electrode is prepared by incorporating the ionophores into plasticized PVC membrane, which is directly coated on the surface of a graphite electrode. The resulting electrode has a linear dynamic range between 1.0 x 10(-1) and 7.9 x 10(-6) M with a near-Nernstian slope of -66.5 +/- 1.0 mV per decade and a detection limit of 6.0 x 10(-6) M. The influences of lipophilic additives on the response properties of the electrode were investigated. The proposed sensor revealed high selectivity for triiodide over a wide variety of other anions and could be used in a pH range 2-9. The electrode can be used for at least 3 months without any considerable divergence in potential. It was applied as indicator electrode in potentiometric titration of ascorbic acid and triiodide ions.