Determination of the Glyphosate Content in Liquid and Dry Formulations by HPLC-UV: Pre-column Derivation with 9-Fluorenylmethyl Chloroformate (FMOC)

Monitoring the glyphosate content of glyphosate-based herbicides requires simple, inexpensive and accessible analytical methods. The objective of this work was to determine by HPLC–UV the glyphosate content of glyphosate-based herbicides after derivatization with 9-fluorenylmethyl chloroformate (FMOC). Glyphosate formulations were simply diluted in ultra-pure water, and derivatization was performed by adding to an aliquot of diluted herbicide, sodium tetra-borate 5% (p/v) and FMOC (10 g L −1 ). After shaking in the dark, the solution obtained was centrifuged at 4500 rpm for 10 min. The supernatant was transferred into a vial for detection and quantification of glyphosate. The mobile phase: The mobile phase was composed of 40 % ammonium acetate (50 mM) and 60% acetonitrile. The stationary phase was a Lichrospher 100 ODS 5 µm (L = 250 cm × ID = 4.6 mm) column maintained at 30 °C. The flow rate was 0.5 mL min −1 , the injection volume was 5 µL and the wavelength was fixed at 254 nm. The coefficients of determination ( R 2 ) were 0.999 for peak height and 0.997 for peak area. The coefficients of variation for repeatability were CV H = 2.52% (peak height) and CV A = 3.92% (peak area). For reproducibility, the coefficients of variation were CV H = 6.87% (peak height) and CV A = 5.33% (peak area). The limits of quantification were 0.524 and 0.1846 mg L −1 for peak height and peak area, respectively. This method is truly suitable because its detection and quantification limits are lower than the glyphosate contents stated on glyphosate-based herbicides.