CHARACTERIZATION OF MIXED ENZYME-MEDIATOR-CARBON PASTE ELECTRODES

Amperometric bioelectrodes based on carbon paste mixed with glucose ox idase (GOX) and dimethylferrocene (DMFc), are characterized by using c yclic voltammetry, potential step chronoamperometry and amperometry at a rotating disk electrode. The catalytic process appears to be highly dependent on the amount of DMFc. Kinetic control, internal diffusion control and external diffusion control can be obtained only by varying the amount of incorporated DMFc. It was shown that the Eadie-Hofstee plot is a particularly useful tool in diagnosis of diffusional limitat ions. The high efficiency of electrochemical regeneration of high amou nts of DMFc surrounding GOX solves the problem of co-substrate transp ort. The catalytic oxidation current of ascorbic acid was highly dimin ished by casting a lipid/Nafion membrane and totally eliminated by tre atment of the sample with hydrogen peroxide prior to measurement.