A rapid, accurate and environment-friendly procedure has been developed for the HPLC-based
determination of benzoic acid and sorbic acid contents in soy sauce. A C18 column served as the stationary
phase, methanol–ammonium acetate buffer (0.02 M) (30:70, v/v) was used as the mobile phase, the
flow rate was 1 mL/min, the UV detector was set at 225 nm and cinnamic acid was selected as an internal
standard. Under such optimized conditions, benzoic acid, sorbic acid and the internal standard were
separated within 8.1 min. This newly developed procedure also showed excellent recurrence, with a relative
standard deviation of less than 3% and recoveries were 96.1–104.3%