Method for Ascorbic Acid Determination with Oxygen Electrode

Abstract

Ascorbic acid (AsA), oxidized specifically by ascorbate oxidase (ASOD) was determined by the measurement of the decrease in dissolved oxygen (DO) in the water sealed, small reaction system of a Clark oxygen electrode. The effects of temperature, pH and buffer concentration of reaction mixture on the DO uptake (mM AsA equivalent) were examined. The most suitable AsA analysis with the oxygen electrode was proved. So far as the analysis for AsA standard solution, a linear relationship was found between the DO uptake and AsA concentration. Furthermore AsA concentration was twice DO uptake, thus making it possible to determine AsA without using a calibration curve. The content of AsA in orange juice sample determined by the present method has a good comparability to that of the 2, 4-dinitrophenylhydrazine (DNP) method and high performance liquid chromatography (HPLC), and the recovery rate of AsA added to the orange juice ranged from 97 to 105%. Thus, this method could be available for the rapid and accurate determination of AsA contents in foods.