Simultaneous analysis of pesticides from different chemical classes by using a derivatisation step and gas chromatography-mass spectrometry

This work presents a new method to analyse simultaneously by GC-MS 31 pesticides from different chemical classes (2,4 D, 2,4 MCPA, alphacypermethrin, bifenthrin, bromoxynil, buprofezin, carbaryl, carbofuran, clopyralid, cyprodinil, deltamethrin dicamba, dichlobenil, dichlorprop, diflufenican, diuron, fenoxaprop, flazasulfuron, fluroxypyr, ioxynil, isoxaben, mecoprop-P, myclobutanil, oryzalin, oxadiazon, picloram, tau-fluvalinate tebuconazole, triclopyr, trifluralin and trinexapac-p-ethyl). This GC-MS method will be applied to the analysis of passive samplers (Tenax ^® tubes and SPME fiber) used for the evaluation of the indoor and outdoor atmospheric contamination by non-agricultural pesticides. The method involves a derivatisation step for thermo-labile or polar pesticides. Different agents were tested and MtBSTFA (N-(t-butyldimethylsilyl)-N-methyltrifluoroacetamide), a sylilation agent producing very specific fragments [M-57], was retained. However, diuron could not be derivatised and the isocyanate product was used for identification and quantification. Pesticides which did not need a derivatisation step were not affected by the presence of the derivatisation agent and they could easily be analysed in mixture with derivatised pesticides. The method can be coupled to a thermal-desorption unit or to SPME extraction for a multiresidue analysis of various pesticides in atmospheric samples.