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 m³ 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.