Determination of Benzoic Acid and Sorbic Acid in Fish Sauce Using HPLC-UV

Abstract

Two preservatives, benzoic acid (BA) and sorbic acid (SA), were quantified in the fish sauce using an HPLC-UV detector. The fish sauce sample was pre-treated using 2 mL of 0.5 M of zinc acetate, Zn(CH3COO)2, and 2 mL of 0.25 M of potassium ferrocyanide, K4[Fe(CN)6], before analysis. The analysis was carried out using HPLC-UV under a mobile phase of methanol: ammonium acetate (0.02 M, pH 6.75) in a ratio 20:80, v/v operating in isocratic mode with 0.8 mL/min flow rate, column temperature of 30 oC, and wavelength of 220 nm. The method yielded linearity in the 25 – 200 mg/L range for BA and SA with R2 of 0.9962 and 0.9985, respectively . The measured LOD was 10 mg/L (S/N ≥3) and LOQ was 30 mg/L (S/N ≥10) for both BA and SA. 21 fish sauce samples, comprising 6 Thai (T1-T6), 4 Vietnamese (V1-V4), and 11 Cambodian (C1-C11) brands, were gathered from several markets in Phnom Penh for examination. It was discovered that 7 fish sauces (33.3% of the samples), consisting of 4 brands from Cambodia and 3 from Vietnam, had BA levels between 33.3 ± 0.4 and 558 ± 2 mg/L. The 14 fish sauces (6 from Cambodia, 2 from Vietnam, and 6 from Thailand), 66.7% of the samples, containing SA ranged in concentration from 19.8 ± 0.7 (<LOQ) to 251 ± 2 mg/L. Only the C4, V2, and V4 contained both BA and SA, however, C5, C9, and V1 could not be detected for BA and SA. The levels of BA and SA found in the fish sauces are below the 1000 mg/L, maximum allowed by Codex Alimentarius.