An improved FIA biosensor for the determination of aspartame in dietary food products.

A flow injection analysis (FIA) biosensor system was developed for the determination of the artificial sweetener aspartame (L-aspartyl-L-phenylalanine methyl ester). The system consisted of an enzyme column of pronase immobilized on activated arylamine glass beads and a L-amino acid oxidase electrode connected in series. The dipeptide bond of aspartame was cleaved by immobilized pronase to release phenylalanine, which was in turn monitored by the enzyme electrode that used L-amino acid oxidase immobilized on a preactivated nylon membrane in combination with an amperometric electrode (platinum vs silver/silver chloride, 700 mV). The response of the FIA biosensor was linear up to 1 mM aspartame with a lower detection limit of 25 microM and had good reproducibility (rsd 0.3%). The FIA biosensor was stable for at least 30 h of continuous use at Tr. Each assay takes 4 min giving a sample throughput of 15 h-1. When applied to aspartame in dietary food products the results obtained agreed well with those reported by the product manufacturers.