Analysis of airborne pesticides from different chemical classes adsorbed on Radiello® Tenax® passive tubes by thermal-desorption-GC/MS.

An analytical methodology using automatic thermal desorption (ATD) and GC/MS was developed for the determination of 28 pesticides of different chemical classes (dichlobenil, carbofuran, trifluralin, clopyralid, carbaryl, flazasulfuron, mecoprop-P, dicamba, 2,4-MCPA, dichlorprop, 2,4-D, triclopyr, cyprodinil, bromoxynil, fluroxypyr, oxadiazon, myclobutanil, buprofezin, picloram, trinexapac-p-ethyl, ioxynil, diflufenican, tebuconazole, bifenthrin, isoxaben, alphacypermethrin, fenoxaprop and tau-fluvalinate) commonly used in nonagricultural areas in atmospheric samples. This methodology was developed to evaluate the indoor and outdoor atmospheric contamination by nonagricultural pesticides. Pesticides were sampled passive sampling tubes containing Tenax® adsorbent. Since most of these pesticides are polar (clopyralid, mecoprop-P, dicamba, 2,4-MCPA, dichlorprop, 2,4-D, triclopyr, bromoxynil, fluroxypyr, picloram, trinexapac-p-ethyl and ioxynil), a derivatisation step is required. For this purpose, a silylation step using N-(t-butyldimethylsilyl)-N-methyltrifluoroacetamide (MtBSTFA) was added before thermal desorption. This agent was chosen since it delivers very specific ions on electronic impact (m/z = M-57). This method was established with special consideration for optimal thermal desorption conditions (desorption temperature, desorb flow and duration; trap heating duration and flow; outlet split), linear ranges, limits of quantification and detection which varied from 0.005 to 10 ng and from 0.001 to 2.5 ng, respectively, for an uncertainty varied from 8 to 30 %. The method was applied in situ to the analysis of passive tubes exposed during herbicide application to an industrial site in east of France.

Coupling ASE, sylilation and SPME-GC/MS for the analysis of current-used pesticides in atmosphere.

An analytical methodology using Accelerated Solvent Extraction (ASE) and a sylilation procedure coupled to Solid Phase Micro-Extraction (SPME) and GC/MS was developed for the determination of 31 pesticides of different chemical classes (urea, phenoxy acids, pyrethrenoïds, etc.) commonly used in non-agricultural areas in atmospheric samples. This methodology was developed to evaluate the outdoor atmospheric contamination by non-agricultural pesticides. Pesticides were simultaneously sampled on glass fibre filters and on XAD-2 resin traps by using a low volume sampler (Partisol) for 1 week. Traps were extracted by Accelerated Solvent Extraction (ASE) with acetonitrile and concentrated to 1 mL by using a rotary evaporator. 500 µL of the extract was dissolved in 19.5 mL of 1.5% NaCl acidified water (pH=3) and SPME extracted by PA fibre for 55 min at 50 °C. Since most of the studied pesticides are polar or thermo-labile, a derivatisation step by injection of 2 µL of MtBSTFA just before SPME desorption was done. MtBSTFA was chosen since it delivers very specific ions on electronic impact (m/z=M-57). Detection limits varied between 5 and 179 ng resin(-1) and between 0.3 and 126 ng filter(-1) corresponding to 2 and 750 pg m(-3) and 30 and 1165 pg m(-3) for 168 m(3) of air pumped through traps. Quantification limits varied between 18 and 595 ng resin(-1) and between 1 and 420 ng filter(-1) corresponding to 107 and 3542 pg m(-3) and 6 and 2500 pg m(-3) for 168 m(3) of air pumped through traps. Uncertainties varied between 7.2% and 39.6% and between 7.2% and 53.4% respectively for filter and resin. The method was used for the analysis of atmospheric samples collected in a background urban site of Strasbourg (east of France) during spring and summer 2010.

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.