Abstract
A lactate sensor system composed of an oxygen electrode, an immobilized lactate oxidase membrane and a personal computer was constructed. The fundamental properties of this sensor were investigated and then the sensor system was applied to the microbioassay of niacin. A linear relationship was obtained between the current decrease of the sensor and nicotinic acid concentrations in the range of 0-16ng/ml. The lactate concentration in the culture medium of Lactobacillus plantarum ATCC 8014 for the microbioassay of niacin was also determined by the enzymatic analysis with lactate dehydrogenase. The values were closely related to those obtained by the lactate sensor system. When the niacin content in various food samples and the nicotinamide con-tent in some vitamin drugs were determined with the lactate sensor system, these values were agreed well to those obtained by the turbidimetry. The lactate sensor system, which was applied to the vitamin determination for the first time in this study, was found to be applicable for practical niacin determination and as a system control equipment.
