AUTOMATED ENZYME PACKED-BED SYSTEM FOR THE DETERMINATION OF VITAMIN-C IN FOODSTUFFS

A microprocessor controlled flow injection system is described for the determination of vitamin C in foodstuffs. The system is based on amperometric detection at a wall-jet electrode coupled with an ascorbate oxidase packed bed. A commercially available Cartesian robotic auto-sampler-dilutor is used as a means of fully automating the sample handling and dilution. Dithiothreitol (DT-T) is used to reduce dehydroascorbic acid to ascorbic acid and to stabilize ascorbic acid standard solutions. Initially, the system was connected in series with a high-performance liquid chromatography column and ultraviolet (UV) detector to allow identification of possible interferents and to allow comparative evaluation of results. The system showed a linear response to the concentration of L-ascorbic acid in the range 1-200-mu-g ml-1 and was capable of detecting total vitamin C in a range of foodstuffs at a sample throughput of 15 samples h-1. Correlations to existing methods of 0.98 were obtained.