A rapid, sensitive and specific high‐pressure liquid chromatographic method was developed to analyse residues of binapacryl, bupirimate and diflubenzuron on mature foliage and fruit at intervals after application of the compounds to Worcester and Cox apple trees. The three compounds were applied as commercial formulations in trials to compare integrated pest management with routine farm spray‐programmes. The identities of the residues were confirmed by a combination of thin‐layer chromatography, ultraviolet spectrometry and gas chromatography/mass spectrometry. Only diflubenzuron persisted on foliage until leaf‐fall. None of the applied compounds was detectable on harvested fruit, the minimum quantifiable residue levels being 1, 5 and 2.5 μg kg−1 fresh weight for binapacryl, bupirimate and diflubenzuron, respectively.
Two methods for the determination of diphenylamine residues in apple peel were devised and used during a fruit storage experiment. One was based on extraction in a Soxhlet apparatus and formation of the fluorobutyryl derivative for electron-capture gas chromatographic determination; the second method used steam distillation and direct determination of diphenylamine with a nitrogen-sensitive thermionic gas chromatographic detector. The latter method, after correction for recovery losses, gave residue levels ca. one-third higher during the 118 days of the storage experiment.phase and column chromatography on alumina or magnesium oxide/Celite, but none of these were successful. A
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