Construction of a p-Nitrophenolate-Sensitive Membrane Electrode and Its Application to an Enzyme Assay

Abstract

A p-nitrophenolate-sensitive membrane electrode was constructed by using tetraheptyl-ammonium chloride as an ion-exchanger and o-nitrophenyl phenyl ether as a membrane solvent. The electrode responded to p-nitrophenolate down to 1μM in a buffer solution of 0.1 M Na₂CO₃- NaHCO₃ (pH 10). The selectivity coefficients of the electrode to typical anions increased in the following order : Cl^-<NO₃^-<SCN^-≈p-nitrophenolate<ClO₄^-. The method was applied to determine the enzyme activity of alkaline phosphatase.