IN-VIVO DETECTION OF FOLPET AND ITS METABOLITE PHTHALIMIDE IN GRAPE MUST AND WINE

Folpet, N-(trichloromethylthio)-phthalimide and its metabolite phthali mide were determined using an HPLC technique in fresh and fermented mu st and wine of Leon Millot grapes treated with fungicides. In the fres hly pressed turbid must, we detected high concentrations of folpet and limited amounts of phthalimide. After 24 hours no folpet was found si nce it had been adsorbed by the yeast cells. In contrast, the phthalim ide concentration increased daily and reached a maximum of 1.36 mg pht halimide/L which corresponds to 2.72 mg folpet/L. Phthalimide was pres ent in all the analyzed, unprocessed, turbid wines. On the other hand, no fungicide residue was found in the filtered wines, and only traces of phthalimide were detected. To study the influence of folpet on the fermentation, the musts from grapes treated with fungicide and from u ntreated grapes were spontaneously fermented. All treated samples bega n to ferment one to five days later than the untreated samples. In two unprocessed, turbid wines of two different grape varieties that recei ved no fungicide treatment, a substance was co-eluted with folpet but could not be chemically attributed to folpet in multicomponent analysi s (MCA). GC-MS analysis showed an eater of a C-18-fatty acid. The most reliable values were obtained in the analyses of unfiltered wines, as all folpet was available as phthalimide.