รายละเอียดเอกสาร

Glyphosate and aminomethylphosphonic acid (AMPA) residues are extracted from crops by maceration with water. The crude extract is partitioned with methylene chloride and then subjected to a cation-exchange (CAX) procedure. The analytes in the purified extract are derivatized directly with a mixture of trifluoroacetic anhydride and heptafluorobutanol. The amine functional groups are derivatized to form the corresponding trifluoroacetyl derivatives. The carboxylic and phosphonic acid functional groups are derivatized to form the corresponding heptafluorobutyl esters. After derivatization, the excess reagents are evaporated, and the residue is dissolved in ethyl acetate. The concentrations of the analytes in the final extract are determined by capillary gas chromatography with mass-selective detection (GC–MSD). Quantitation is performed by the external standard method with calibration solutions derivatized concurrently with the extracts. In this method, a highly sensitive detection system allows small amounts of aqueous crop extract to be derivatized without evaporation, thereby overcoming difficulties associated with derivatization of aqueous extracts and analyte adsorption. The limit of quantitation (LOQ) is 0.05 mg/kg.