Determination of ascorbic acid in soups by high-performance liquid chromatography with electrochemical detection

Determination of ascorbic acid (AA) in soups was performed by high-performance liquid chromatography with electrochemical detection set at 400 mV vs an Ag/AgCl reference electrode. This method was suitable for the determination of AA in soups. The proposed method was simple, rapid (analysis time similar to 8 min), sensitive [detection limit similar to 0.1 ng per injection (20 mu L) (at a signal-to-noise ratio of 3:1)], highly selective, and reproducible [relative standard deviation similar to 3.1% (n = 5)]. The calibration graph of AA was linear in the range of 0-16 ng per injection (20 mu L). Recovery of AA was >90% by the standard addition method. Periodical changes of AA in soup were also examined. it was found that AA standards diluted with both tap water and hot tap water were very unstable, and AA in soup prepared with hot tap water (>90 degrees C) according to the label was very stable.