Analysis of Glyphosate and AMPA in Environmental Water by Ion Chromatography Electrospray Tandem Mass Spectrometry (IC-ESI-MS/MS)

Importance of the Topic

Glyphosate is the most widely used nonselective herbicide globally and degrades to AMPA in soil. Trace levels of both compounds are frequently detected in environmental waters raising health and regulatory concerns. The US EPA limit for glyphosate in drinking water is 0.7 mg/L and demands sensitive analytical methods for compliance and monitoring.

Objectives and Study Overview

This study aims to develop a direct, derivatization-free analytical method using two-dimensional ion chromatography coupled with electrospray tandem mass spectrometry (IC-ESI-MS/MS) to separate, identify and quantify glyphosate and AMPA in environmental water matrices at sub-ppb levels.

Methodology

A two-dimensional anion exchange approach was implemented: the first dimension isolates target analytes from high concentrations of chloride, carbonate, nitrate and sulfate, while the second dimension refines separation and delivers a clean eluent to the mass spectrometer. Samples were injected directly without pretreatment. Potassium hydroxide eluent was generated electrolytically and suppressed postcolumn to produce a MS-compatible mobile phase. Gradient conditions enabled full separation within 30 minutes.

Used Instrumentation

• Dionex ICS 3000 ion chromatography system with IonPac AG19/AS19 and AG21/AS21 column sets, UTAC concentrator, EGC-KOH eluent generator, and ASRS suppressors.
• Thermo Scientific TSQ Quantum Access triple quadrupole mass spectrometer with negative mode ESI source (spray voltage 3000 V, capillary temperature 400 C, collision gas 1.5 bar).

Main Results and Discussion

The method achieved baseline resolution of glyphosate, AMPA and major matrix anions in under 30 minutes. Calibration curves for AMPA (110 → 63 and 110 → 79 transitions) and glyphosate (168 → 150 and 168 → 79) exhibited linearity (R2 ≥ 0.996) over 0.05–50 ppb. Method detection limits in a simulated high ionic matrix were 0.313 ppb for AMPA and 0.252 ppb for glyphosate, well below EPA Method 547 requirements. Recoveries of 97.2% (AMPA) and 82.1% (glyphosate) were obtained at 5 ppb spiking, with RSDs < 5% without internal standards. Stability studies indicated potential sample degradation over time, suggesting use of refrigerated autosamplers or isotopically labeled standards for long runs.

Benefits and Practical Applications

This IC-ESI-MS/MS workflow eliminates the need for derivatization and extensive sample preparation, reduces matrix interference through multidimensional separation, and delivers high sensitivity suitable for regulatory compliance in environmental monitoring of water quality.

Future Trends and Applications

Further improvements may include broader application to other highly polar pesticides, integration of isotopic internal standards for quantitation, automation for high throughput, and method adaptation for diverse environmental and industrial matrices. Technological advances in microfluidics and portable IC-MS systems may enable on-site rapid screening.

Conclusion

The presented two-dimensional IC-ESI-MS/MS method provides a robust, sensitive, and streamlined approach for direct analysis of glyphosate and AMPA in complex water matrices, meeting stringent detection requirements without derivatization and enhancing laboratory efficiency.

Reference

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6. US EPA. Consumer Factsheet on Glyphosate. 2008.
7. US EPA. Method 547: Glyphosate in Drinking Water by HPLC. 2008.