High-performance liquid chromatography with electrochemical detection of aspartame with a post-column photochemical reactor

Abstract

Aspartame (N- l-α-aspartyl- l-phenylalanine 1-methyl ester) was determined by high-performance liquid chromatography with electrochemical detection. Aspartame, which is electrochemically inactive, was made oxidizable in the range 0.1–1.1 V after post-column irradiation at 254 nm. A detection limit of 0.5 mg/l (signal-to-noise ratio 3:1) was attained using a coulometric detector with the working cell set at 0.8 V and a C 6 column (150 × 4.6 mm I.D.) operated under isocratic conditions with 0.1% perchloric acid-methanol (85:15, v/v) as the eluent at a flow-rate of 1 ml/min. A linear response for aqueous solutions of aspartame in the range 1–20 mg/l and a 5% standard deviation for five replicate injections were obtained. The method was applied to the determination of aspartame in two diet colas and a pharmaceutical product. Chromatograms and a hydrodynamic voltammogram are shown.