SIMULTANEOUS GAS-CHROMATOGRAPHIC DETERMINATION OF FOOD PRESERVATIVES FOLLOWING SOLID-PHASE EXTRACTION

A simultaneous method for the solid-phase extraction of five preservat ives is presented. Of the different sorbent materials assayed, styrene -divinylbenzene polymers provided the highest adsorption efficiency. S amples are inserted into the flow system at pH 1, which results in inc reased selectivity. Elution is made with 150 mu l of ethyl acetate and 2 mu l aliquots of the eluate are manually injected into a gas chroma tograph equipped with flame ionization detection. Of the two chromatog raphic columns of different polarity, that containing the more polar s tationary phase assayed provided the better results by virtue of the a cid character of the analytes. The limits of detection achieved range from 0.1 to 0.2 mg/l, and the precision is quite high (R.S.D.<4%). The potential of the proposed method was assessed by applying it to the d etermination of sorbic and benzoic acid in feeds. Solid samples requir e pretreatment involving liquid-liquid extraction, evaporation of the extract and dissolution of the residue in 0.1 M HNO3. Recoveries ca. 9 5% for p-hydroxybenzoic acid esters can thus be obtained. (C) 1998 Els evier Science B.V. All rights reserved.