HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH ELECTROCHEMICAL DETECTIONOF ASPARTAME WITH A POSTCOLUMN PHOTOCHEMICAL REACTOR

Aspartame (N-L-alpha-aspartyl-L-phenylalanine 1-methyl ester) was dete rmined by high-performance liquid chromatography with electrochemical detection. Aspartame, which is electrochemically inactive, was made ox idizable in the range 0.1-1.1 V after post-column irradiation at 254 n m. A detection limit of 0.5 mg/l (signal-to-noise ratio 3:1) was attai ned using a coulometric detector with the working cell set at 0.8 V an d a C-6 column (150 x 4.6 mm I.D.) operated under isocratic conditions with 0.1% perchloric acid-methanol (85:15, v/v) as the eluent at a fl ow-rate of 1 ml/min. A linear response for aqueous solutions of aspart ame in the range 1-20 mg/l and a 5% standard deviation for five replic ate injections were obtained. The method was applied to the determinat ion of aspartame in two diet colas and a pharmaceutical product. Chrom atograms and a hydrodynamic voltammogram are shown.