Comparison of gas chromatography and immunoassay methods in quantifying fenitrothion residues in grape juice processed into alcoholic drinks

Wine and Arak, the national alcoholic drink in Lebanon, were prepared from grape juice fortified with fenitrothion to a concentration of 20ppm. Sample s of the 11 fractions produced by the fermentation and distillation steps w ere analyzed for fenitrothion residues using gas chromatography (GC) and en zyme-linked immunosorbent assay (ELISA). Results of residue analyses showed that the two techniques were highly correlated (r = 0.978) and indicated t hat fenitrothion was stable during the fermentation steps but not during di stillation. The clarified wine 35 days later contained about 85% (15.3 ppm) of the fenitrothion concentration found in the juice as determined by GC a nalysis. Arak was prepared by a two-steps distillation of the clarified win e. The alcohol distillate and undistilled fraction from the first distillat ion contained 2.5 ppm and 5.8 ppm of fenitrothion, respectively. No fenitro thion residues were detected by both techniques in the four fractions colle cted from the second distillation step.