Determination of glyphosate and (aminomethyl)phosphonic acid in soil, plant and animal matrices, and water by capillary gas chromatography with mass-selective detection

A residue method for the determination of glyphosate [N-(phosphonomethyl)glycine, PMG] and its principal metabolite, (aminomethyl)phosphonic acid (AMPA), in soil, crops, animal products, and water was developed. PMG and AMPA were extracted from soil using a mixture of 0.25 M NH4OH and 0.1 M KH2PO4, from crops with water, and from animal products with either 0.1 N HCl or 0.6% acetic acid. Extracts of crops and animal products were cleaned up on a cation exchange column. Soil extracts, purified extracts of crops and animal products, and water samples were directly reacted with a mixture of heptafluorobutanol and trifluoroacetic anhydride. Derivatized analytes were quantified by using capillary gas chromatography and a mass-selective detector operated in the selected-ion-monitoring mode. The limit of quantitation was demonstrated to be as low as 0.01 mg/kg for each analyte. For PMG, the mean recoveries from soil, crops, animal matrices, and water ranged from 90 to 100% with coefficients of variation (CV) ranging from 6 to 14%. For AMPA, the mean recoveries ranged from 89 to 103% with CVs ranging from 8 to 13%.