Rapid determination of glufosinate, glyphosate and aminomethylphosphonic acid in environmental water samples using precolumn fluorogenic labeling and coupled-column liquid chromatography

The approach presented in recent work [J.V. Sancho et al., J. Chromatogr. A, 678 (1994) 59] concerning the rapid determination of glufosinate in environmental water samples was successfully applied to the development of efficient procedures including the assay of glyphosate and its main metabolite, aminomethylphosphonic acid (AMPA). The methodology involves two approaches: (i) a multi-residue method allowing the simultaneous determination of the three analytes in environmental water samples to a level of 1 mu g/l or (ii) single residue methods focused on the analysis of a single analyte to the sub-mu g/l level. The procedures involve a precolumn derivatisation step with 9-fluorenylmethylchloroformate (FMOC-Cl) yielding highly fluorescent derivatives of the analytes which then can be determined by coupled-column LC with fluorescence detection using a reversed-phase C-18 column (C-1) coupled to a weak ion-exchange column (C-2). The separation power of the first column (C-1) was used to achieve sensitivity, by injecting large volume samples, and automated sample clean-up was achieved by removing the less polar interferences, including the excess of hydrolysed reagent (FMOC-OH). Using these procedures, glufosinate, glyphosate and AMPA were successfully recovered from water samples at 0.50-10 mu g/l fortification levels, with a sample throughput of at least 40 samples per day.