Development of a headspace solid-phase microextraction/gas chromatography–mass spectrometry method for determination of organophosphorus pesticide residues in cow milk

Abstract

In the past few years, organophosphorus compounds become one of the most widely used classes of pesticides due to their acute toxicity against a wide variety of pests. In this work, a method based on solid-phase microextraction in mode headspace (HS-SPME) coupled to gas chromatography–mass spectrometry (GC–MS) was developed and optimized throughmultivariate factorial design to determine residues of organophosphorus pesticides in cow's milk. Different parameters of the method were evaluated, such as fiber type, temperature, extraction and desorption times, sample volume, effect of salt addition and stirring velocities. The evaluated pesticideswere dichlorvos, sulfotep, demeton-S, dimpylate, disulfoton, parathion,methylparathion, fenitrothion, chlorpyrifos and ethion. The best results were obtained using polydimethylsiloxane/divinylbenzene fiber and headspacemode at 90 °C for 45 min, alongwith stirring at 600 rpmand desorption for 5 min at 250 °C. Under the optimized conditions, the proposed methodology was able to determine all of the pesticides with variation coefficients between 6.1% and 29.5%. Detection and quantification limits ranged from 2.16 to 10.85 μg L−1 and from 6.5 to 32.9 μg L−1, respectively. To evaluate residues of these pesticides inmilk, cows were exposed to the pesticides of interest andmilkwas collected after 24 h. The developedmethodwas able to detect traceamounts of these pesticides in the collected milk samples.