A new method for the extraction of pesticide residues from soil was developed, optimized, validated and applied to real samples. The technique consisted of combining single-drop microextraction and solid-liquid extraction with low temperature partitioning (SLE/LTP-SDME) followed by analysis using gas chromatography with electron capture detection (GC/ECD). This method was used to determine the presence of alachlor, methyl parathion, trifluralin, endrin, lindane, dieldrin and dichloro-diphenyl-trichloroethane (4,4’-DDT) in soil samples. Recoveries ranging from 67.2 to 122.5% were achieved, coefficients of variation (repeatability) were lower than 22.4% and limits of detection ranged from 0.18 to 0.59 µg kg-1. Recovery from soils fortified with different concentrations of the pesticides ranged from 61.5 to 123.5%. The new method combines the primary advantages of the two techniques: purification of the sample using SLE/LTP and preconcentration using SDME. The new method also enables the determination of low volatility compounds without requiring the sample to be heated.
Keywords:
soil; pesticide; single-drop microextraction; solid-liquid extraction with low temperature partitioning
