RAPID-DETERMINATION OF GLYPHOSATE RESIDUES AND ITS MAIN METABOLITE AMPA IN SOIL SAMPLES BY LIQUID-CHROMATOGRAPHY

Efficient procedures for the trace-level determination of glyphosate a nd/or the metabolite AMPA in various type of soil samples has been dev eloped. After extraction in alkaline media an aliquout of the extract is neutralized prior to a precolumn derivatisation step with FMOC-Cl y ielding highly fluorescent derivatives of the analytes. Two different LC-methods have been applied. The first one is focussed at the determi nation of glyphosate only and requires a liquid-liquid extraction step with ethyl acetate for the removal of the reagent excess prior to the RPLC-analyses performed on a single 25 cm C18 column under isocratic elution conditions. The second method makes use of coupled-column LC f or on-line sample cleanup of diluted extracts and allows the determina tion of both glyphosate and AMPA. With the developed procedures glypho sate and AMPA were succesfully recovered from different kind of soils at 400 and 40 ng g(-1) fortification levels. Sample throughput is at l east 20 samples per day. Depending on the type of soil, viz. high or l ow clay content and organic matter, and the LC method used, limits of determination range between 100 and 10 ng . g(-1) for both analytes.