Determination of glyphosate and aminomethylphosphonic acid in soils by HPLC with pre-column derivatization using 1,2-naphthoquinone-4-sulfonate.

A simple selective high-performance liquid chromatography (HPLC) method has been developed for the determination of glyphosate and its main metabolite aminomethylphosphonic acid residues in soil samples based on a pre-column derivatization with 1,2-naphthoquinone-4-sulfonate (NQS). The reaction is performed at pH 9.4 and 60C for 5 min. The separation of glyphosate was carried out in a C18 column using a 1% acetic acid?methanol (40:60, v/v) mobile phase and UV detection. An experimental design approach based on the central composite design is used to investigate the dependence of the derivatization variables of pesticide. The concentration of NQS and reaction temperature were found to be statistically significant. The limits of detection obtained were 0.064 mg kg?1 for glyphosate and 0.098 mg kg?1 for its metabolite. The proposed method was successfully applied to the analysis of real soil samples from corn crops. The proposed method is easier and faster compared to other ones.