Determination of Fungicide Residues in Peach Trees

The residue analyses of three fungicides, thiram, captan and benomyl, have been accomplished in peach trees. Thiram was extracted with hexane:ethyl acetate (80:20 v/v) and determined after a column cleanup by reverse-phase HPLC with a mixture of acetonitrile:0.3 ammonia at 280 nm. Captan was extracted with acetonitrile:water (2:1) and determined by GLC-ECD after a partition and a column clean-up. Benomyl was extracted with ethyl acetate and determined, as MBC, by reverse-phase HPLC with methanol:0.3 ammonia, after a partition and a column clean-up. Recoveries through the methods were always higher than 70%. The detection limits were 0.5 ppm for thiram, 0.02 ppm for captan and 0.2 ppm for benomyl, based on a 5 g sample. Residue levels in peach twigs, treated with fungicide solutions, are reported.