Development of a one-step microwave-assisted extraction method for simultaneous determination of organophosphorus pesticides and fungicides in soils by gas chromatography-mass spectrometry

A one-step microwave-assisted extraction (MAE) procedure was developed for the simultaneous extraction of organophosphorus pesticide and fungicide residues in soil which have been greatly used in agriculture. Parameters that could influence the MAE efficiency such as irradiation power, temperature, time and solvent were investigated, and extraction efficiencies in the range of 92.6−103.7% were obtained using 400 W (100% output) at 160 °C for 10 min with only 12 mL of acetone-hexane (2:1, v/v). The analytes in extracts were analyzed directly by gas chromatography-mass spectrometry (GC-MS) without any further cleanup. At 5 and 50 ng g−1 fortification levels for each analyte, the average recoveries obtained were ranged from 70.0% to 120.0% with relative standard deviation (RSD) between 0.2% and 14%. The method was linear over 1-250 ng g−1 with a correlation coefficient (r2) between 0.9916 and 0.9966. The detection limits (S/N=3) were between 0.10 and 0.12 ng g−1. The applicability of the method was demonstrated by analyzing field soil samples collected from six intensive horticultural sites in Ethiopia.