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 base d on a reaction of AsA with copper(II) at pH 5.0 to form a readily oxi dizable species, followed by electrochemical detection at an applied p otential of +20 mV vs. Ag/AgCl. Under the optimum conditions a linear calibration curve was obtained for AsA over the concentration range fr om 0.1 to 20 mu M with a sample volume of 20 mu l. The relative standa rd deviation of the peak height for 10 mu M AsA was 1.0% (n=10). The m ethod was successfully applied to the determination of AsA in fresh fr uit juices and soft drinks. The obtained results are in good agreement with those obtained by high-performance liquid chromatography (r=0.99 4).