GC-ECD DETERMINATION OF CHLORPYRIFOS, ITS OXON, AND 3,5,6-TRICHLORO-2-PYRIDINOL IN SOIL, ELM BARK, AND LITTER FOLLOWING APPLICATION FOR CONTROL OF THE ELM BARK BEETLE

An analytical method has been developed for the simultaneous determina tion of residues of chlorpyrifos, and its main metabolites, the oxon a nd 3,5,6-trichloro-2-pyridinol in elm bark, Litter, and soil following use in the control of the elm bark beetle, the principle vector of Du tch elm disease in the Canadian prairie provinces. The residues of chl orpyrifos, oxon, and pyridinol were extracted with methanol under acid ic conditions from elm bark, litter, and soil, cleaned up by liquid-li quid partitioning, and simultaneously chromatographed by GC-ECD after the pyridinol had been derivatized with diazomethane. The average reco veries of chlorpyrifos, oxon, and pyridinol in all tested matrices in three replicates ranged from 90 to 102% with standard deviations of 0. 4 to 8.2%.