Concentration-step amperometric biosensors using thin enzyme reactors

Abstract The thin carbon felt impregnated with a glucose oxidase solution or an immobilized ascorbate oxidase carbon felt was placed on the gas permeable membrane of a Clark Oxygen electrode and concentration-step bio-amperometry of glucose and vitamin C ( l -ascorbic acid and dehydroascorbic acid) was carried out. The decreased current peaks are proportional to the amount of substrate, the relative standard deviations of the peak values were found to be below 5% and the lifetime of the immobilized ascorbate oxidase reactor was extended to 90 days. The steady-state amplified concentration-step amperometric current response of vitamin C using a cyclic reaction of vitamin C was obtained and the amplification factor of vitamin C was about 3 when pH 7.5 buffer solution with 5 × 10 −3 M dithiothreithol was impregnated in the carbon felt.