Determination of glyphosate in soils by HPLC with pre-column derivatization using 4-chloro-7-nitro-1,2,3-benzoxadiazole

A simple selective high-performance liquid chromatography (HPLC) method has been developed for the determination of glyphosate residue in soil samples based on a pre-column derivatization with 4-chloro-7-nitro-1,2,3-benzoxadiazole (NBD-Cl). Soil samples were extracted by 0.6 mol/L KOH solution. Glyphosate was derivatized with NBD-Cl in 0.125 mol/L sodium tetraborate medium (pH = 9.0-10.5). The reaction was completed after 80 min at 60 ℃. A elution consisting of a mixture of 0.02 mol/L Na₂HPO₄ solution and methanol (70 : 30, V/V) was used to separate the amine derivatives in a C₁₈ column at room temperature. Diode array detector was applied at 500 nm. The correlation coefficient for the method was 0.9999 at the concentration ranging from 0.01 to 2.0 mg/L. The limits of quantification was 0.02 mg/kg. The average recoveries of glyphosate spiked at 0.02, 0.1and 10 mg/kg levels in soil samples were between 82% and 93%, and the relative standard deviations (RSD) were between 2.5% and 3.9%.The method is simple, rapid and suitable for the confirmation and quantification of GLUF in soil.