Behavior of field-applied triadimefon, malathion, dichlorvos, and their main metabolites during barley storage and beer processing.

The behavior and fate of 3 pesticides (triadimefon, malathion, and dichlorvos) and the main metabolites (triadimenol and malaoxon) during barley storage or beer processing were assessed using a pilot-plant equipment. The residues of all products were determined using liquid chromatography coupled with tandem mass spectrometry. Field investigation of the dissipation rate kinetics for triadimefon and malathion during storage indicated that their half-life was twice as high when 5 times the recommended dosage was used. Milling had little effect on the removal of dichlorvos and malathion residues, whereas these were substantially removed when the spent grains were filtered after mashing. The calculated processing factors were all <1, indicating the residual ratios of dichlorvos and malathion were reduced during the entire process. In conclusion, storage and processing considerably reduced pesticide residue levels in barley and beer; however, greater focus needs to be paid to the toxicity of their metabolites in commercial by-products.