Scientists Reveal New Method for Soil Pesticide Detection Based on UHPLC-MS/MS

In a recent study published in the journal Agriculture, a group of scientists from Mexico developed a new method for detecting herbicides in agricultural soil, using techniques such as 9-fluorenylmethyl chloroformate (FMOC-Cl) and ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) (1).

Farmer spraying pesticide during sunset time | Image Credit: © bannafarsai - stock.adobe.com

Millions of tons of pesticides are used across the world each year and can prove dangerous to human health when accumulating in the environment. Glyphosate is a popular herbicide that eliminates weeds in agriculture, forestry, and urban environments, with global consumption being 126 milion kg in 2014, with an expected sales increase of 6% by 2024 (1). Glyphosate is usually absorbed by cells via foliar content, but residual glyphosate can seep into soil, where microorganisms degrade it into a metabolite, aminomethylphosphonic acid (AMPA), which has a much longer half-life than glyphosate. These two substances, along with glufosinate, which is an herbicide used for broadcast burndown application prior to planting or emergence of canola, corn, soybean, and other plants, can lead to significant contamination in the environment, in places like groundwater, surface water, air, soil, dust, and food (2).

There are existing methods meant for determining these glyphosate, AMPA, and glufosinate residue, including liquid extraction (LE) followed by derivatization and subsequent quantification by HPLC-MS/MS; ultraviolet/visible (UV) detector; and diode array, amongst many others. The goal of this study was to validate a simple, efficient, and cost-effective method for the determination of these substances. Specifically, the scientists’ technique involves phosphate buffer extraction that involves derivatization with 9-fluorenylmethyl chloroformate (FMOC-Cl) and subsequent quantification by UHPLC-MS/MS. According to the scientists, their method differs from others due to “a simple derivatization, with a one-step extraction, for the determination at trace levels of glyphosate, AMPA, and glufosinate” (1). The scientists said this method would also help save resources in the reagents and consumables normally used in extraction, on top of having a shorter execution time.

After testing the method with the different types of residues, the results proved effective. The method exhibited a linear range of 5.0 to 600 µg/kg with limits of detection of 1.37, 0.69, and 1.22 µg/kg and limits of quantification of 4.11, 2.08, and 3.66 µg/kg for glyphosate, AMPA, and glufosinate, respectively. Furthermore, the method’s procedures showed promising repeatability and reproducibility, with coefficients of variations less than 8.0% and recovery percentages typically landing between 93.56% and 99.10%. Each analyte had their matrix effects calculated, with the results encouraging the scientists and their belief in their method. From there, the method was applied to 46 soil samples collected from Mexican crop fields, all of which held different concentrations of AMPA. According to the scientists, their efforts proved successful. Although further research is needed, this method could be applicable to other types of analytes and comparable matrices (such as sediments).

References

(1) Leyva-Morales, J. B.; Cabrera, R.; Bastidas-Bastidas, P. d. J.; Valenzuela-Quintanar, A. I.; Pérez-Camarillo, J. P.; González-Mendoza, V. M.; Perea-Domínguez, X. P.; Márquez-Pacheco, H.; Amillano-Cisneros, J. M.; Badilla-Medina, C. N.; Ontíveros-García, L. A.; Cruz-Acevedo, E. Validation and Application of Liquid Chromatography Coupled with Tandem Mass Spectrometry Method for the Analysis of Glyphosate, Aminomethylphosphonic Acid (AMPA), and Glufosinate in Soil. Agriculture 2023, 13, 1131. DOI: https://doi.org/10.3390/agriculture13061131

(2) Glufosinate Herbicide. Minnesota Department of Agriculture 2023. https://www.mda.state.mn.us/glufosinate-herbicide (accessed 2023-12-13)