Development of a liquid-liquid extraction method for the determination of pyrimethanil, metalaxyl, dichlofluanid and penconazol during the fermentative process of must by GC-NPD

Abstract

BACKGROUND: A rapid, selective and sensitive gas chromatographic method is described for the analysis of four fungicides - pyrimethanil, metalaxyl, penconazol and dichlofluanid, widely used in vineyards - in must and wine, as well as samples during alcoholic fermentation. The effect of alcoholic fermentation on pyrimethanil concentration in synthetic and real musts was studied. RESULTS: The proposed method was based on liquid-liquid extraction followed by gas chromatography with nitrogen-phosphorus detector. n-Hexane was the most appropriate solvent for extracting the target fungicides in synthetic and real samples. Quality parameters of the proposed method presented good recovery (ca 78.3% for almost all compounds) and precision (between 1.4% and 6.1%), and quantification limits lower than maximum residue limits. However, for dichl of luanid recovery levels of well over 100% were found. CONCLUSIONS: There was no matrix effect in the analysis of pyrimethanil, metalaxyl or penconazol, but this effect was observed for dichlofluanid in synthetic and real matrices. The application of the fermentative process on pyrimethanil fungicide caused a high decrease in the concentration of this compound, and no product appeared in degradation. The decrease of pyrimethanil in fermented samples was similar in both synthetic and real samples. © 2009 Society of Chemical Industry.