Sequential injection analysis-based flow system for the enzymatic determination of aspartame Original Research Article

The versatility of sequential injection analysis systems as a sampling handling approach combined with the flexibility of the individual solenoid valves was conjugated for the automatisation of the proposed new enzymatic method for the determination of aspartame in commercial sweetener tablets. The method involves the enzymatic conversion of aspartame in hydrogen peroxide by the α-chymotrypsin–alcohol oxidase system, followed by the use of 2,2′-azinobis(3-ethylbenzthiazolin-sulfonic acid-6) (ABTS) as electron donor for peroxidase. α-Chymotrypsin and alcohol oxidase enzymes were immobilised on activated porous silica beads. No activity loss in the reactors was detected throughout 60 days. The calibration plots were linear up to 350 mg l−1, with a detection limit of 2.16 mg l−1 of aspartame. Relative standard deviations (R.S.D.) of 3.0 and 2.4% (n=10) for samples containing 25.8 and 51.9 mg l−1 of aspartame, respectively, were obtained. The method was applied to the determination of aspartame in commercial sweetener tablets; the results obtained were compared to those provided by a HPLC method and revealed no statistical differences for a 95% confidence level.