Determination of L-Ascorbic Acid by a Flow Injection Analysis with Copper(II)-Mediated Electrochemical Detection

An electrochemical method has been developed for the determination of L-ascorbic acid (AsA) by a flow injection analysis. The method is based on a reaction of AsA with copper(II) at pH 5.0 to form a readily oxidizable species, followed by electrochemical detection at an applied potential of +20mV vs. Ag/AgCl. Under the optimum conditions a linear calibration curve was obtained for AsA over the concentration range from 0.1 to 20μM with a sample volume of 20μl. The relative standard deviation of the peak height for 10μM AsA was 1.0% (n=10). The method was successfully applied to the determination of AsA in fresh fruit juices and soft drinks. The obtained results are in good agreement with those obtained by high-performance liquid chromatography (r=0.994).