Linear Dependence of the Potential of “Wired” Glucose Oxidase Electrodes on the Concentration of Glucose

Abstract

Potentiometric assays, unlike amperometric or coulometric ones, do not require accurate definition and knowledge of the area of the measuring electrode or microcell volume. Their potential scales, however, with the logarithm of the concentration of the analyte, while in amperometric, chronoamperometric, or chronocoulometric assays the charge or current scales linearly with the concentration. Here we show that in a potentiometric glucose assay the potential can scale linearly with concentration. Such scaling is realized when the electrode is coated with a resistive, but nevertheless electron-conducting, film where glucose is electrooxidized. The film consists of a redox polymer film that “wires” reaction centers of covalently co-immobilized glucose oxidase to the electrode. After a potential pulse is applied to the “wired” enzyme electrode so that the electrode-bound redox centers are electrooxidized, the floating electrode potential decays to a value that varies linearly with the concentration of glucose.