Analysis of diflubenzuron by gas chromatography/mass spectrometry using deuterated diflubenzuron as internal standard

A new and rapid gas chromatographic/mass spectrometric analytical procedure for insect growth regulator diflubenzuron, a phenylurea-based insecticide, has been developed. Diflubenzuron is decomposed by the heat of a gas chromatograph into three reproducible fragments, 4-chlorophenyl isocyanate, 4-chloroaniline, and 2,6-difluorobenzamide, which elute separately from the GC column. The source of the chloroaniline appears to be the thermal breakdown of chlorophenyl isocyanate. No difluorobenzoic acid is generated, confirming that the heat-labile bond of diflubenzuron is different from the bond cleaved during based-catalyzed hydrolysis or microbial degradation. Advantage is taken of this along with the use of dideuterated diflubenzuron as an internal standard, and the selected ion monitoring capability of mass spectrometry, to enable analysis of diflubenzuron in complex extracts of vegetation samples without purification or derivatization. Detectability levels are similar to or better than those of currently used methods. Extraction and analysis of diflubenzuron from dosed leaves demonstrate the selectivity and utility of the technique