Rapid method for the analysis of a variety of chemical classes of pesticides in surface and ground waters by off-line solid-phase extraction and gas chromatography-ion trap mass spectrometry

Abstract

A rapid multiresidue method for the analysis, at trace levels, of 96 target analytes in field water samples has been developed. Pesticide parent compounds, from a variety of chemical and biological classes, as well as some of their major conversion products, were included in the target analyte list. Analytes were extracted from 1-1 filtered water samples by off-line solid-phase extraction (SPE) on three tandem Sep-Pak C 18 cartridges. The sorbed analytes eluted with ethyl acetate were directly analysed by gas chromatography-ion trap mass spectrometry (GC-IT-MS), the mass spectrometer operated in the electron impact (EI) ionisation mode. The mean recoveries, at the 0.5 μg/l fortification level, for two-thirds of the analytes ranged from 75 to 120%; the recoveries for less than one third of the analytes ranged from 50 to 75% and the recoveries for the 10 relatively most polar analytes ranged from 12 to 50%. The limit of detection (LOD) of the method for 69 analytes was better than 0.01 μg/l; the LOD for eighteen analytes was better than 0.05 μg/l; for captan, carbofenothion, decamethrin, demeton-S-methyl sulphone, fensulfothion, deisopropylatrazine and metamitron, the LOD was 0.1 μg/l and for chloridazon and tetradifon, it was 0.5 μg/l. Identification, in full scan mode, was made at S/ N≥3. Quantification, for the majority of the analytes, was made at the base mass. The system was evaluated for monitoring pesticides in surface and ground water samples of Macedonia, Greece.