A simple method for the determination of glyphosate residues in soil by capillary gas chromatography with nitrogen phosphorus

A simple method was developed to determine the residues of glyphosate, N-(phosphonomethyl)glycine, in soil. The residues were extracted from soil matrices with 2 M NH4OH, derivatized by trifluoroacetic anhydride and trifluoroethanol, and, then, determined by gas chromatography with a nitrogen-phosphorus detector (GC-NPD). The results were further confirmed by gas chromatography-mass spectrometry (GC-MS). The limit of detection was estimated to be 9 × 10−12 g, and the minimum determination concentration of glyphosate in the samples was 0.01 mg/kg. The ranges for the average recoveries and relative standard deviation (RSD) of the method were 84.4–94.0% and 8.1–13.7%, respectively, in agreement with the directives for method validation in residue analysis. The proposed method was successfully employed for the determination of glyphosate residue levels and dissipation retes in the soil from an apple orchard.