Analysis of triallate residues in cereals and soil by gas chromatography with ion-trap detection.
Triallate residues in barley seedlings and soil samples were determined by gas chromatography with ion-trap detection. Soil was extracted with methanol on a mechanical shaker, and plants were extracted with acetonitrile in a Sorvall homogenizer. After evaporation of the organic solvents, the residue was dissolved in hexane, and plants extracts were cleaned-up on an alumina column. Gas chromatographic analysis was carried out using a BP-1 fused-silica capillary column with helium as carrier gas. To quantitate residues the total-ion chromatogram was obtained and then the selected-ion monitoring chromatograms were displayed at m/z 86 for triallate and at m/z 154 for the internal standard, methyl-(4-amino-2-chloro)-benzoate. The average recovery through the method from barley and soil samples was always higher than 80%. The limit of detection in the selected-ion mode was 0.01 mg/kg. Barley and soil samples treated with triallate were also analysed. A good agreement was observed between results obtained by this method and by gas chromatography with nitrogen-phosphorus detection.
Application of capillary gas chromatography with mass selective detection to pesticide residue analysis
Abstract A random sample of 76 pesticides with good gas chromatographic properties has been collected in order to test the applicability of the mass selective detector HP MSD for pesticide residue analysis. Using a capillary column, mass spectra of good quality were produced with 10 or 20 ng of each pesticide. Seventy two compounds were not only identified at this concentration with the PBM (probability based matching) search routine in the NBS library, but also remarkably with the best fit in the corresponding hit list. Lower concentrations can be detected only with selected ion monitoring (SIM). A mixture of 18 chlorinated pesticides was added to green pepper at the 10 ppb level. All compounds were detected with SIM using special time programming in one gas chromatogaphic analysis. The detection sensitivity of the mass selective detector in SIM mode approaches that of established selective detectors. The reliability of the results with respect to the identity of a pesticide residue, however, is orders of magnitude better. Therefore, this detector is a valuable tool for performing confirmatory analysis.
THE EFFECT OF PLACEMENT AND CONCENTRATION OF 2,3-DCDT ON THE SELECTIVE CONTROL OF WILD OATS IN WHEAT
A series of experiments on different soils and with varying concentrations demonstrated that the herbicidal activity of 2,3-DCDT (2,3-dichloroallyl diisopropylthiolcarbamate3) is primarily via the coleoptile rather than the root system of wild oats and wheat. The degree of this activity differed between the two species depending on the stage of development when they came in contact with treated soil, the concentration of the herbicide and the length of time that the coleoptile was in contact with treated soil. In wild oats there were two distinct periods of high sensitivity, namely, during the initial half-inch of coleoptile growth and a later stage which appeared to coincide with the initiation of the crown node. Wheat was highly sensitive at only the early period. This crop was tolerant to sufficiently high concentrations of 2,3-DCDT, when planted at least a half-inch below a surface layer of treated soil, to permit the selective control of wild oats in wheat. However, the relative placements were criti...