Dialkyl phosphates are organophosphate insecticide metabolites and their urinary analysis is useful for assessing human exposure to these compounds. This study presents a sample preparation method with microwave-assisted derivatization for two dialkyl phosphates to make the process faster before gas chromatographic analysis. The optimized conditions for derivatization procedure were: 250 μL of 2,3,4,5,6-pentafluorobenzyl bromide 3% in acetonitrile for derivative; microwave for 5 min with intensity of 160 W. The electron ionization mass spectrometric analysis was performed using a gas chromatography with mass spectrometry QP-2010 from the Shimadzu(®) equipped with RTx(®) -5MS capillary column. Ions were monitored at selected-ion monitoring mode at m/z 350 for diethyl thiophosphate and m/z 366 for diethyl dithiophosphate. The developed method was linear for both metabolites. The intra-assay precision was the values ranged between 1.1 and 9.1%, for diethyl thiophosphate, and between 4.06 and 6.9%, for diethyl dithiophosphate. The interassay precision showed relative standard deviation between 10.3 and 15.1%, for diethyl thiophosphate and between 4.9 and 11.9%, for diethyl dithiophosphate. The results obtained suggests that derivatization assisted by microwave, before gas chromatography with mass spectrometry analysis, can be applied to monitoring of exposure to organophosphates once is fast, sensible, and precise method to determinate dialkyl phosphates.
Keywords: Dialkyl phosphates; Gas chromatography with mass spectrometry; Microwave-assisted derivatization.
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