Measurement of Underivatized Glyphosate and Other Polar Pesticides in Surface and Drinking Water

Significance of the Topic

Monitoring trace levels of glyphosate and other polar pesticides in water is critical for public health and environmental quality. Due to their high polarity and low concentrations, these compounds pose analytical challenges that require sensitive, robust methods.

Objectives and Overview of the Study

This work presents a simple, derivatization-free LC-MS/MS approach for quantifying glyphosate, AMPA, glufosinate, MPPA, HEPA, NAG, ethephon, and fosetyl in surface and drinking water at sub-µg/L levels. The method integrates streamlined sample preparation, reversed-phase chromatography, and tandem mass spectrometry detection.

Methodology and Instrumentation

Sample Preparation:

• Filtration of water samples through 0.2 µm PES filters.
• Acidification to 0.1% formic acid and direct injection without dilution.

Chromatography:

• Agilent 1290 Infinity II LC with Poroshell 120 CS-C18 column (2.1 × 150 mm, 2.7 µm).
• Mobile phases: A = 0.1% formic acid + 5 µM deactivator additive in water; B = 0.1% formic acid in methanol.
• Gradient elution over 8 min, 25 µL injection, column at 40 °C.

Mass Spectrometry:

• Agilent 6470A Triple Quadrupole with Jet Stream ESI.
• Dynamic MRM acquisition in positive and negative modes.
• Capillary voltage: +3000 V/−3500 V; gas and sheath gas optimized for sensitivity.

Main Results and Discussion

• Method detection limit for glyphosate: ~10 ng/L.
• Limit of quantitation: 10–100 ng/L, with accuracies between 82–120% in drinking and river water.
• Calibration curves exhibited excellent linearity (R² > 0.998) across 0.005–10 µg/L, with quadratic fits for glufosinate where needed.
• Chromatographic peak shapes were maintained by the deactivator additive and PEEK-lined tubing, mitigating metal-induced tailing.
• Reproducibility studies yielded MDLs of 6.1–8.6 ng/L across multiple days and columns.

Benefits and Practical Applications

• No derivatization or extensive sample handling reduces analysis time and costs.
• Large aqueous injections improve sensitivity for trace-level pesticides.
• Use of common acidic mobile phases allows straightforward integration into routine LC/MS workflows.
• Robust peak shapes and reproducible quantitation support regulatory and quality-control applications.

Future Trends and Applications

The method can be expanded to additional polar analytes and complex matrices. Future developments may include high-resolution mass spectrometry, further miniaturization of sample preparation, on-site screening tools, and greener chemistries that reduce solvent consumption.

Conclusion

This Agilent workflow effectively addresses the challenges of analyzing underivatized polar pesticides in water. Integrating optimized sample preparation, Poroshell CS-C18 chromatography, and sensitive triple quadrupole MS enables reliable quantitation at low ng/L levels for environmental monitoring and compliance testing.

References

1. Zweigenbaum J, Lucas D, Cali A. Direct Analysis of Glyphosate, AMPA, and Other Polar Pesticides in Food. Agilent Technologies Application Note 5994-0796EN; 2019.
2. Hsiao JJ, et al. Improved LC/MS Methods for the Analysis of Metal-Sensitive Analytes Using Medronic Acid as a Mobile Phase Additive. Analytical Chemistry. 2018;90(15):9457–9464.
3. US Environmental Protection Agency. Procedures for Detection and Quantitation – Documents; 2019.