Direct and simultaneous determination of ascorbic acid and glucose in soft drinks with electrochemical filter/biosensor FIA system

An FIA system capable of the direct and simultaneous determination of ascorbic acid and glucose in commercial soft drinks is described. The system features a flow-through electrolysis cell (electrochemical filter, ECF) for a coulometric determination based on the quantitative electrolysis of ascorbic acid and a glucose oxidase monolayer electrode for the amperometric determination of glucose. Although ascorbic acid interferes with the glucose biosensor, quantitative electrooxidation in the ECF supresses the error. The glucose biosensor did not exhibit saturation for 0.1 M-order glucose samples. The measured values for nine commercial soft drinks without any pretreatment, such as dilution, showed a good correlation to those determined with conventional methods.