Determination of 24 pesticides residues in mineral and peat soils by modified QuEChERS method and gas chromatography

Abstract

A simple extraction and cleanup procedure has been developed for the analysis of 24 organophosphorus (OP), organochlorine (OC) and pyrethroid (PY) pesticides in mineral and peat soils using modified QuEChERS method. The pesticides were extracted from the soil with acidified acetonitrile. The water was removed from the extract by salting out with sodium chloride and addition of magnesium sulfate. For OP pesticides, the extracts were cleaned up with 0.2 g of primary secondary amine packed in glass Pasteur pipette and determined by gas chromatography with flame photometric detector. For OC and PY pesticides, the extracts were cleaned up with 0.2 g of silica gel packed in a glass Pasteur pipette and determined by gas chromatography with electron capture detector. After the cleanup, the extracts had lower colour intensity and reduced matrix interferences. The recovery of the OP and OC pesticides for mineral and peat soils determined at 0.01–1.0 mg kg⁻¹ fortification levels ranged from 79.0–120.0% and 82.2–117.6%, respectively. The detection limits for OP and OC pesticides were 0.001–0.01 and 0.002–0.005 mg kg⁻¹, respectively. The recovery of the PY pesticides ranged from 87.5–111.7% at the detection limits of 0.002–0.010 mg kg⁻¹. The relative standard deviations for all pesticides studied were below 10.8%. The modified method was simple, fast, and had utilized less reagents than the conventional methods. The method was applied to the determination of the pesticide residues in mineral and peat soil samples collected from the vegetable farms.

Keywords:

• gas chromatography
• pesticides
• rapid method
• recovery
• soils

Acknowledgements

The authors wish to thank the staff of the Pesticides Residue Laboratory for their technical assistance and Dr GB Teh for editing the manuscript.