Direct Analysis of Glyphosate, AMPA, and Other Polar Pesticides in Food

Significance of the Topic

Glyphosate and its polar metabolites are among the most widely used agrochemicals globally. Concerns over their potential health and environmental impacts have driven regulatory bodies to set stringent limits in food and water. Reliable, sensitive analytical methods are essential to ensure product safety, meet regulatory requirements, and support public confidence in food quality.

Aims and Study Overview

This study aimed to develop a direct ion-exchange LC/MS/MS method for simultaneous quantification of glyphosate, AMPA, HEPA, MPPA, glufosinate, N-acetyl glufosinate, ethephon, fosetyl, and related polar pesticides in various food matrices. The goal was to achieve detection at low parts-per-billion levels with minimal sample cleanup and high throughput.

Methodology and Instrumentation

Sample Preparation and Reagents:

• QuPPe extraction protocol in polypropylene tubes: internal standards added before extraction to correct matrix effects.
• Mobile phases: water, 50 mM ammonium bicarbonate, and acetonitrile; fresh preparation to minimize background.

Chromatographic Separation:

• Ion-exchange column (quaternary amine bound to polyvinyl alcohol, 2.1×100 mm).
• Gradient elution from high organic to high aqueous buffer to sharpen early eluting polar compounds.

Mass Spectrometry:

• Agilent 6495A triple quadrupole with negative-mode ESI and MRM monitoring.
• Optimized transitions, collision energies, and dwell times for each analyte and stable isotope analogue.

Main Results and Discussion

Chromatography delivered sharp, well-resolved peaks for all target analytes in under 20 min. Calibration in solvent was linear from 1 to 100 ppb (r² > 0.99). Method limits of quantification (MLOQs) in food matrices ranged from 0.1 ppb (HEPA) up to 7.5 ppb (AMPA, glufosinate), depending on the commodity and compound. Recovery studies at 10 ppb showed 80–120 % for analytes with internal standards, while higher recoveries at 100 ppb confirmed method accuracy. Matrix suppression was effectively compensated by stable isotope internal standards added prior to extraction.

Benefits and Practical Applications

This direct LC/MS/MS approach offers:

• Low ppb detection with minimal derivatization or cleanup.
• Robust performance across diverse food matrices (fruits, grains, wines).
• High throughput for routine QA/QC and regulatory monitoring.

Future Trends and Opportunities

Potential developments include further miniaturization of flow paths, coupling with high-resolution MS for non-target screening, automation of sample prep, and extending the method to environmental water and soil analysis to support broader monitoring of polar agrochemicals.

Conclusion

The presented ion-exchange LC/MS/MS method with a fully bio-inert flow path and stable isotope standards provides a sensitive, reliable, and efficient solution for routine analysis of glyphosate, AMPA, and other polar pesticides in food at low ppb levels.

Reference

• Boocock MR, Coggins JR. Kinetics of 5-Enolpyruvylshikimate-3-phosphate synthase inhibition by glyphosate. FEBS Lett. 1983;154(1):127–133.
• IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. Some Organophosphate Insecticides and Herbicides: Diazinon, Glyphosate, Malathion, Parathion, Tetrachlorvinphos. IARC Monogr Eval Carcinog Risks Hum. 2015;112.
• European Commission. Ban Glyphosate and Protect People and the Environment from Toxic Pesticides. Communication from the Commission on the European Citizens’ Initiative. 2017.
• European Food Safety Authority. Peer review of the pesticide risk assessment of the potential endocrine disrupting properties of glyphosate. EFSA Journal. 2017;15(9):e04979.
• Ortiz MJ, Lawler JL. Jury orders Monsanto to pay $289 million to cancer patient in Roundup lawsuit. USA Today. 2018.
• 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), version 9.3. EURL-SRM; 2017.