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Abstract

A direct injection gas chromatography (GC) instrument equipped with an intermediate polar column (CP-SIL 8CB, 30 m × 0.53 mm) was used to determine nine preservatives (including sorbic acid, dehydroacetic acid, benzoic acid, methyl paraben, ethyl paraben, isopropyl paraben, propyl paraben, isobutyl paraben and butyl paraben) in vinegar, soy sauce, pickle condiment liquid and fish sauce. A water soluble compound 1,4-dihydroxybenzene (DHB) was used as an internal standard. The detection limits of the above preservatives were found to be lower than 0.5 ppm. A recovery study was performed by spiking 200 μg target compounds into 1 ml of vinegar or soy sauce and then analyzed by GC. Results showed the recoveries of the above nine preservatives were in the range of 95-106% with coefficients of variation less than 7.2%. These results indicate that the direct injection GC method is an accurate, simple and rapid method to simultaneously screen and quantify sorbic acid, dehydroacetic acid, benzoic acid and six parabens in liquid foods without further sample preparation. Thirty-seven liquid food samples of vinegar, soy sauce, pickle condiment liquid and fish sauce were analyzed using the developed method. The contents of sorbic acid, benzoic acid, dehydroacetic acid, and 6 parabens in vinegar samples were found to be 0-407, 0-519, 0 and 0-102 μg/mL; in soy sauce samples were 0-311, 0-266, 0 and 0-243 μg/mL; in pickle condiment liquid samples were 0-462, 0-3, 0 and 0-209 μg/mL; and in fish sauce samples were 0-1044, 0-266, 0 and 0-163 μg/mL, respectively. Results also showed most of the test samples were fortified with two or more preservatives. Thirteen out of 14 samples labeled "preservative-free" were detected to be preservative containing products. The total preservative contents in some test samples were over the regulation levels of 100 "g/mL in vinegar and 500 "g/mL in soy sauce or fish sauce.

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