Automated enzyme packed-bed system for the determination of vitamin C in foodstuffs

Abstract

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 (DTT) 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 µg 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.