A Sandwich Enzyme Electrode Giving Electrochemical Scavenging of Interferents

A ‘sandwich’ bielectrode system is described for a glucose oxidase amperometric electrode, which uses an outer scavenger electrode to remove ascorbic acid interference from the measurement of enzyme generated hydrogen peroxide. An Au grid electrode is proposed as the scavenger, which can be coated with Teflon (AF 1600), to provide a substrate diffusion limiting barrier and thus extend the linear range of the electrode. A small sample: enzyme ratio is investigated, whereby the glucose from the sample is depleted during the measurement, such that a ‘total’ glucose measurement can be obtained by integration of the current signal. The integrity of the measurements are compared in the presence and absence of ascorbic acid and it is shown that the scavenger electrode is able to remove about 80% of the ascorbate from reaching the inner Pt working electrode. This preliminary system model is briefly tested with samples of lemon juice and the ascorbate interference removal demonstrated.