Matrix solid-phase dispersion extraction and determination by high-performance liquid chromatography with fluorescence detection of residues of glyphosate and aminomethylphosphonic acid in tomato fruit

A method based on matrix solid-phase dispersion (MSPD) is described for the quantitative extraction of glyphosate and its major metabolite aminomethylphosphonic acid (AMPA) from tomato fruit. After application of 120 μL of HNO3 1 M to the sample, the dispersion column was packed with 0.5 g of sample blended into 1 g of NH2-silica. Two aqueous fractions were obtained. First, AMPA was eluted from the column using deionized water (F1), and then a NaH2PO4 0.005 M solution was used for the elution of glyphosate (F2). Cleanup of F1 and F2 was made by ion exchange chromatography on a SAX anion exchange silica. Determination was done by HPLC with fluorescence detection after precolumn derivatization with 9-fluorenylmethylchloroformate (FMOC-Cl). Mean recoveries calculated at fortification levels of 0.5 μg/g for glyphosate and 0.4 μg/g for AMPA were 87% and 78%, respectively. The relative standard deviations (n = 7) for the total procedure were 10% and 16%. Detection limits were 0.05 μg/g for glyphosate and 0.03 μg/g for AMPA.