Simultaneous determination of preservatives in beverages, vinegar, aqueous sauces, and quasi-drug drinks by stir-bar sorptive extraction (SBSE) and thermal desorption GC-MS

A method for the simultaneous determination of seven preservatives - sorbic acid, benzoic acid, and p-hydroxybenzoic acid ethyl, isopropyl, propyl, isobutyl, and butyl esters - in beverages, vinegar, aqueous sauces, and quasi-drug drinks has been developed using the stirbar sorptive extraction technique then thermal desorption GC-MS analysis. The extraction conditions - pH, sample volume, extraction temperature, salt addition, and extraction time - were examined. d(5)-Benzoic acid and p-hydroxybenzoic acid sec-butyl ester were added as surrogate internal standards to compensate for the effect of sample matrix and coexisting analytes on the sorptive extraction. The linearity of the method was good over the concentration range from I to 1000 mug mL(-1) for sorbic acid, 10-1000 mug mL(-1) for benzoic acid, and 0.1-100 mug mL(-1) for p-hydroxybenzoic acid ethyl, isopropyl, propyl, isobutyl, and butyl esters, and the correlation coefficients were higher than 0.9984. The limit of detection ranged from 0.015 to 3.3 mug mL(-1). The recoveries (95-105%) and precision (RSD: 0.86-6.0%) of the method were examined by analyzing a sparkling soft drink, white wine, red wine, balsamic vinegar, soy sauce, and quasi-drug drink samples fortified at the 5 to 50 mug mL(-1) level.