Analysis of organophosphorus pesticides in honeybee by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry

Pesticides applied in extended agricultural fields may be controlled by mea ns of bioindicators, such as honeybees, in which are the pesticides bioaccu mulate. Liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) experiments with positive (PI) and negative (ND ion modes were optimized for the analysis of 22 organophosphorus pesticides in honeybee samples. The extraction required 3 g of sample, which was extr acted with acetone. The extract was purified with coagulating solution and reextracted with C12CH2. Pesticides studied could be detected by both ioniz ation modes except for parathion, parathion-methyl, and bromophos, which di d not give signals in PI mode, and triazophos, which was not detected in NI mode. Fragmentation voltage and vaporizer temperature were optimized to ac hieve the highest sensitivity. The spectra profile of each pesticide in PI mode showed the [M + H](+) ion as the main signal, whereas in NI mode only fragment ions were shown. The detection limit obtained in selected ion moni toring mode ranged from 1 to 15 mug kg(-1). The average recoveries from spi ked honeybees at various concentration levels (0.5-5 mg kg(-1)) exceeded 65 % with relative standard deviations of 4-15%. The method was applied to rea l samples, in which residues of coumaphos and dimethoate were detected.