Determination of glyphosate in soil/sludge by high performance liquid chromatography

- The sodium phosphate solution was first considered as extracting solution for the extraction of glyphosate (Glyp) in the soil/sludge samples.
- Trisodium citrate was added to the extracting solution in order to eliminate the interference caused by metal ions in the soil/sludge.
- The extract solution was decontaminated by liquid- liquid extraction with hexane and it could avoid using SPE cartridges reported previously which is troublesome and expensive.

In order to evaluate the pollution caused due to glyphosate (Glyp) in soils and sludge, it is important to establish a set of standard determination techniques. In this work, the previously reported HPLC analytical method for determination of Glyp has been improved in order to be applied for all kinds of soils/sludge. The soil/sludge samples were extracted using sodium phosphate and trisodium citrate aqueous solutions. The extract was adjusted to pH 9 and contaminations were removed by washing with n-hexane. The method developed in this work further involves derivatization with 9-fluorenylmethylchloroformate (FMOC-Cl) followed by high performance liquid chromatography (HPLC) coupled with fluorescence detection. The method was validated in three soil (red soil, black soil and paddy soil) and two sludge samples (lake and river sludge) from China and verified in six laboratories. A good linear relationship (correlation coefficients ≥0.999) was observed within the range of 0.005-0.5 mg/L. The limit of detection (LOD) and the limit of quantitation (LOQ) were determined to be 0.01 mg/kg and 0.04 mg/kg, respectively. The precision and accuracy were satisfactory with the relative standard deviation (RSD) lower than 15% and the mean recovery values ranging from 75% to 110% (n = 6), that spiked at three levels (0.1, 0.5 and 1.0 mg/kg).