Analysis of glyphosate, AMPA and 7 other polar pesticides in food and water by SAX chromatography with MS/MS detection

Significance of the Topic

Glyphosate, a phosphonate-based herbicide, and its primary metabolite AMPA are broadly applied in agriculture and increasingly scrutinized for environmental and food safety reasons. The high polarity and surface adsorption characteristics of these compounds create analytical challenges, driving the need for a sensitive, reproducible method capable of quantifying trace levels in complex food and water matrices.

Objectives and Study Overview

The study aims to develop and validate a direct, high-throughput method for simultaneous determination of glyphosate, AMPA and seven other polar pesticides in food and environmental water. Key goals include overcoming matrix effects, achieving low-ppb limits of quantitation, and ensuring consistent system-to-system performance.

Methodology

• Sample Preparation: Solid and high-water content food samples (≥80%) were extracted via the QuPPe protocol using acidified methanol, adjusting water levels for consistency across matrices.
• Chromatographic Separation: Strong anion exchange on a HILIC VT50 2D column with a ternary gradient of water, ammonium bicarbonate buffer and acetonitrile provided baseline separation of nine polar analytes.
• MRM Optimization: Negative electrospray ionization transitions were optimized to distinguish isobaric fragments, particularly to avoid cross-interference between fosetyl and AMPA due to shared fragment ions.

Instrumentation

• Agilent 1260 Infinity Bio-inert Quaternary LC system
• Shodex HILIC VT50 2D analytical column
• Agilent 6495A Triple Quadrupole mass spectrometer with ESI source

Main Results and Discussion

Baseline chromatographic resolution was achieved for nine target compounds in both aqueous standards and QuPPe extracts, although the extraction solvent altered relative retention times. Notably, fosetyl and AMPA exhibited co-elution in extraction solvent, necessitating precise gradient control to separate overlapping MRM transitions arising from fosetyl’s 13C isotope. Calibration curves for glyphosate demonstrated linearity from 1 to 100 ppb (R2 > 0.99).

Benefits and Practical Applications

This approach enables reliable quantitation of highly polar pesticides in low-protein, high-water foods with recoveries exceeding 80% for fruits and vegetables; a representative sample (corn) yielded ~50% recovery. Using an all-PEEK flow path minimizes metal surface interactions, enhancing reproducibility. The method attains limits of quantitation below 10 ppb in high-water content matrices, meeting stringent regulatory requirements.

Future Trends and Opportunities

Emerging applications include extending the protocol to environmental water monitoring, integrating high-resolution accurate mass detectors for non-target screening, and implementing automation for higher sample throughput. Ongoing column and reagent innovations may further reduce matrix effects and analysis time.

Conclusion

The developed SAX-LC-MS/MS method offers a robust, sensitive workflow for direct analysis of glyphosate, AMPA and related polar pesticides in diverse food and water samples. Its high reproducibility, low detection limits and broad applicability support routine monitoring in quality control and environmental studies.

References

• Anastassiades M et al. Quick method for the analysis of numerous highly polar pesticides in foods of plant origin via LC-MS/MS involving simultaneous extraction with methanol (QuPPe-Method). EU Reference Laboratory for pesticides requiring Single Residue Methods. 2016.
• Goodwin L et al. Tandem mass spectrometric analysis of glyphosate, glufosinate, aminomethylphosphonic acid and methylphosphinicopropionic acid. Rapid Commun Mass Spectrom. 17(9):963-969. 2003.