Bienzymatic potentiometric electrodes for creatine and l-arginine determination

Abstract

Ammonium-selective electrodes enzymatically sensitized for creatine and l-arginine are presented. Enzyme layers of these biosensors contain two enzymes: urease and, as a second enzyme, creatinase or arginase dependent on the analyte (substrate): creatine or arginine. The bienzymatic layer with such a composition sequentially converts the analyte into ammonium ions, which are detectable by the internal sensor. Monomolecular and bimolecular bienzymatic layers immobilized directly on the ammonium sensitive membrane were used. The covalent binding of enzymes to the matrix of the ion-selective membrane made of the carboxylated poly(vinyl chloride) was performed using carbodiimide and glutaraldehyde. The extremely thin enzyme layers are strongly bound and easily penetrable. Therefore the presented biosensors are stable and respond rapidly, t 95% varies from 1.5 to 4 min. The linear ranges of both biosensors were 0.1–30 mM and the detection limits were below 10 −5 M.