Chloride Ion Sensor Based on Sol-Gel-Derived Membranes Modified Chemically with Porphyrin-Manganese(III) Complexes

Abstract

Porphyrin-manganese(III) complexes were used as Cl⁻-selective ionophores for sol-gel derived membranes encapsulating and binding covalently them. The ion-sensing membrane encapsulating the ionophore showed hardly any EMF response to Cl⁻-activity changes, probably because the ionophore was not uniformly dispersed in the sol-gel-derived membranes. On the other hand, the ion-sensing membrane binding covalently the ionophore, in which the ionophore was dispersed in the membranes uniformly, showed near-Nernstian responses to Cl⁻-activity changes. The sol-gel-derived membranes were relatively Cl⁻-selective over interfering hydrophobic anions, as compared with the case of the membranes containing only a cationic additive. The Cl⁻-selective electrode is, therefore, promising for applications to clinical analysis in the future.