Gas chromatographic flow method for the preconcentration and simultaneous determination of antioxidant and preservative additives in fatty foods.

A partially automated gas chromatographic method for the simultaneous determination of antioxidants (tert.-butyl-4-hydroxyanisole, 2,6-di-tert.-butyl-p-hydroxytoluene, tert.-butylhydroquinone, alpha-tocopherol and alpha-tocopheryl acetate) and preservatives (sorbic acid, benzoic acid and their esters) in fatty foods without derivatization is reported. About 95% of triglycerides from lipid material are avoided by manually extracting the samples with a mixture of solvents and the remaining by using a continuous solid-phase extraction system. By using aqueous sample solutions (in 0.1 M HNO3), XAD-2 sorbent and selective elution with 200 microliters of 2-propanol, only ca. 0.03% of total triglycerides present in the original sample remains in the final extract. Manual injection of the extract into a GC-flame ionization detection allows the additives to be determine at concentrations in the range 0.5-100 micrograms/ml with a high precision (ca. 3%). Mass spectrometry in the conventional electron impact mode, in conjunction with library search, permits the unequivocal identification of all the additives. Margarine, oil, cheese, paté and sauce samples were analysed in this way, all with good results.