A rapid method for the simultaneous determination of preservatives in soy sauce

A rapid method for the simultaneous determination of five preservatives is presented. The preservatives from soy sauce samples were extracted with a C18 bonded silica SPE cartridge from soy sauce samples. 10% Methanol in 1% phosphoric acid solution was found to be the best solution for clean-up. The preservatives were eluted with methanol and determined by high-performance liquid chromatography using a gradient elution system in one run. The average recoveries of p-hydroxybenzoic acid, benzoic acid, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate and butyl p-hydroxybenzoate are 97, 96, 95, 93 and 92 %, respectively. The calibration curves arewere linear between 1.8 and 54 mg/kg. The regression coefficients arewere acceptable (R 2 > 0.992). This method is a useful protocol for routine examination of the preservative constituents in soy sauces.