Abstract:

A method based on gas chromatography-tandem mass spectrometry (GC-MS/MS) coupled with accelerated solvent extraction (ASE) was developed for the determination of eight organochlorine pesticides (OCPs) and five organophosphorus pesticides (OPPs) in soils. The soil samples were grinded after freeze-drying. Particles with diameters lower than 250 μm were chosen by ion-sieving. After this, 10.0 g soil mixed with 2.0 g diaomite was extracted with hexane-acetone (1:1, v/v). The extracts were dehydrated with anhydrous sodium sulfate and concentrated with a termovap sample concentrator. The concentrated solutions were further cleaned up with Si SPE columns and eluted with hexane-acetone (1:1, v/v). The purified solutions were then isolated by HP-5MS column (30 m×0.25 mm×0.25 μm) and detected using the multiple reaction monitoring mode at the electron impact source. It is observed that this method has good linearities in the range of 1.00-100 μg/L for the 13 compounds, and the correlation coefficients (R) were greater than 0.995. The spiked recoveries of the 13 compounds were in the range of 66.8%-88.4%, and the relative standard deviations were less than 10%. With 10.0 g of sampling weight, the method detection limits ranged from 0.02 to 0.04 μg/kg for the eight OCPs and from 0.06 to 0.12 μg/kg for the five OPPs. This method is suitable for the determination of trace OCPs and OPPs in soils.

Key words: accelerated solvent extraction (ASE), gas chromatography-tandem mass spectrometry (GC-MS/MS), organochlorine pesticides (OCPs), organophosphorus pesticides (OPPs), soil