MULTI-RESIDUE PESTICIDE ANALYSIS IN SOIL BY SOLID-PHASE DISK EXTRACTION AND GAS-CHROMATOGRAPHY ION-TRAP MASS-SPECTROMETRY

A rapid and reproducible multi-residue analysis was developed for the simultaneous determination of 46 pesticides belonging to triazines, or ganophosphorus and organochlorine compounds, carbamates, anilides, ani lines, and amides in various soil samples. Soil samples including its natural water contents were extracted with a mixture of methanol/water (3/1, v/v). The aqueous methanol extracts were directly transferred t o an extraction reservoir containing 1 L of reagent water and subjecte d to clean-up and enrichment by an SPE membrane workstation on Empore C-18 disks. The analytes were eluated, concentrated and analyzed witho ut additional treatment by gas chromatography/ion-trap mass spectromet ry (GC-ITDMS). Recoveries of the analytes using this procedure ranged from 65 to 102% measured at 20-200 mu g/kg spiked levels for 41 pestic ides tested. With 10 g of soil sample, the detection limits were betwe en 0.5 and 25 mu g/kg. The disk SPE procedure was compared to the soxh let extraction, and comparable recoveries and precisions were demonstr ated for most of the pesticides studied.