Chemically amplified current response of vitamin C based on the cyclic reaction between l-ascorbic acid and dehydroascorbic acid, using dithiothreithol and ascorbate oxidase.
A cyclic reaction between the reduced and the oxidized forms of vitamin C takes place by combining the ascorbate oxidase reaction and the reduction of l-ascorbic acid to dehydroascorbic acid by dithiothreithol. l-Ascorbic acid is oxidized by the dissolved oxygen and its consumption is not compensated by the chemical regeneration of l-ascorbic acid from dehydroascorbic acid. The dissolved oxygen then continues to decrease during the cyclic reaction, consequently, the decrease of the reduction current of oxygen is amplified. The amplification factor of 5 x 10(-5)Ml-ascorbic acid at 5 x 10(-3)M dithiothreithol and pH 7.5 was found to be 10.6 when enzyme activity is 0.64 units/ml and the reaction time is 10 min.
Uchiyama
S
S
Department of Environmental Engineering, Saitama Institute of Technology, 1690 Fusaiji, Okabe, Saitama 369-02 Japan.