The Development of a Glucose Enzyme Electrode

An investigation has been undertaken into the suitability of sulphanilic acid carbons as electrode materials and as enzyme electrode materials specifically. The carbons, prepared at a range of heat treatment temperatures between 700k and 1400K have been characterised for their physical and chemical characteristics, with particular emphasis on electrical and surface functional group phenomena. The work has lead to an understanding of the carbonisation behaviour of the sulphanilic acid carbons and to a partial structural elucidation. The carbons are shown to be amorphous semiconductors, incorporating carbon, hydrogen, nitrogen, sulphur and oxygen, the oxygen moiety being associated with acidic surface oxides. The electrical conductivity mechanisms of these carbons have been shown to be explained by the Mott and Davis model for semiconduction in amorphous materials. The overall structural data is consistent with the recently proposed spheroidal carbon networks (Kroto et al, 1986). The carbons have been incorporated into an electrode assembly and electrochemical investigations undertaken. Electrodes formed from sulphanilic acid carbons prepared at 1400K have beem shown to respond potentiometrically to solution pH with approximately Nernstian behaviour. Cyclic voltammetric studies have been performed in several solutions and in the presence of two redox couples. The Fe(CN)se-4/Fe(CN)e-3 couple has been shown to behave in accordance with the Erev mechanism for electron transfer, by both classical cyclic voltammetric interpretation and by convolution potential sweep voltammetry. This behaviour is of interest due to the lack of electrode surface preparation employed. The 1400K sulphanilic acid carbon electrode has also been used as the basis of an amperometric enzyme electrode. The electrodes, employing covalently immobilised glucose oxidase, have been shown to be capable of quantitative glucose measurement through monitoring electrochemical peroxide decomposition. Certain other parameters such as_ pH, temperature and mediator influences have also been studied.