Use of an amino acid in the mobile phase for the determination of ascorbic acid in food by high-performance liquid chromatography with electrochemical detection

The possibility of using monosodium l-glutamate (MSG) (20 mM MSG, pH 2.1) in the mobile phase for the determination of ascorbic acid (AA) in foods by high-performance liquid chromatography (HPLC) with electrochemical detection was examined. The hydrodynamic voltammogram of AA and the background current were also examined. The applied potential was set at 400 mV versus an Ag/AgCl reference electrode. It was demonstrated that MSG was a useful mobile phase for the determination of AA in foods. This paper also examines the stability of AA under various conditions in order to optimize HPLC conditions and the pre-run sample stabilization. The proposed method is simple, rapid (analysis time: ∼6 min), sensitive (detection limit: ∼0.1 ng per injection (5 μl) at a signal-to-noise ratio of 3), highly selective and reproducible (relative standard deviation: ∼2.5%, n=7). The calibration graph of AA was linear in the range 0.1–50 ng per injection (5 μl). Recovery of AA was over 90% by the standard addition method.