Improved sample pretreatment of the carbon disulfide evolution method for the determination of dithiocarbamate residues in lettuce

摘要: In this study the sample pretreatment of carbon disulfide evolution method for determination dithiocarbamate residues in lettuce, described by Keppel, was examined and improved. The following observations were made. distribution dithiocarbamates lettuce heads is uneven. By deheading mixing leaves, taken analysis insufficiently homogeneous. relative standard deviation varies from 10 to 34%. Thiram (a widely used dithiocarbamate) decomposes rapidly chopped (50% within half an hour). When hydrochloric acid (2.4 M) containing stannous chloride added immediately after chopping, decomposition does not occur. existing (deheading mixingof leaves) compared with modified (chopping addition) samples field treated thiram as well zineb. mean results both methods correspond well, a much higher reproducibility method. 1 4%.