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

Importance of the Topic

The widespread use of glyphosate as a nonselective herbicide and its persistence in environmental waters raise concerns about human health and ecosystem integrity. Regulatory limits for glyphosate in drinking water necessitate sensitive, accurate methods capable of detecting low part per billion levels amid complex sample matrices. An analytical approach that eliminates derivatization and extensive sample preparation streamlines monitoring efforts and improves laboratory throughput.

Study Objectives and Overview

This work aimed to develop a two-dimensional ion chromatography tandem mass spectrometry method to separate and quantify glyphosate and its primary degradation product AMPA directly from water samples without derivatization. The study presents the coupling of high-purity eluent generation and anion suppression with electrospray ionization MS/MS detection to achieve robust analysis in 30 minutes.

Methodology and Instrumentation

Water samples were injected directly into a Dionex ICS-3000 system with on-line potassium hydroxide eluent generation. A first IC dimension employed an IonPac AG19/AS19 column and an Ultratrace concentrator to remove major matrix ions. A second dimension utilized IonPac AG21/AS21 to refine analyte peak shape before MS introduction. Electrolytically generated KOH gradients ranged from 1 to 40 mM over the run. Suppression was achieved with ASRS 300 devices at optimized currents. MS analysis used a TSQ Quantum Access triple-quadrupole in negative ESI mode with selective reaction monitoring of transitions 110→63 and 110→79 for AMPA, and 168→150 and 168→79 for glyphosate.

Used Instrumentation

• Dionex ICS-3000 ion chromatography system
• Eluent generator cartridge for KOH production
• ASRS 300 anion self-regenerating suppressors
• IonPac AG19/AS19 and AG21/AS21 columns with guard and separator
• Ultratrace anion concentrator column
• Thermo Scientific TSQ Quantum Access triple quadrupole MS with ESI source

Results and Discussion

The two-dimensional IC effectively separated glyphosate, AMPA, and high-abundance matrix anions (chloride, nitrate, carbonate, sulfate) in under 30 minutes. Calibration curves exhibited excellent linearity across 0.05 to 50 ppb for glyphosate and 0.1 to 50 ppb for AMPA with R2 values ≥ 0.996. Method detection limits in a simulated high-ionic matrix were 0.252 ppb for glyphosate and 0.313 ppb for AMPA, significantly below EPA thresholds. Recoveries at 5 ppb spike level were 82.1% for glyphosate and 97.2% for AMPA, with relative standard deviations under 5% without internal standards. Some signal degradation over extended runs suggests benefits from refrigerated autosampling and isotopically labeled standards to enhance stability.

Benefits and Practical Applications

• Direct aqueous injection eliminates time-consuming derivatization and sample cleanup
• High sensitivity and specificity via MS/MS SRM transitions
• Improved source cleanliness through multidimensional suppression of matrix ions
• Rapid analysis suitable for QA/QC laboratories and environmental monitoring

Future Trends and Applications

Integration of isotopically labeled internal standards and temperature-controlled autosamplers will enhance method precision and stability. Advances in multi-dimensional chromatography could expand direct analysis to other highly polar contaminants. Coupling with high-resolution mass spectrometry and automation will further improve detection limits and throughput for environmental monitoring and regulatory compliance.

Conclusion

This IC-ESI-MS/MS technique provides a rapid, derivatization-free approach for quantifying glyphosate and AMPA in environmental waters at sub-ppb levels. The two-dimensional separation strategy enhances analyte resolution and protects the MS source from matrix fouling, delivering robust performance in complex samples.

References

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2. United States Geological Survey. Glyphosate Found in Wastewater Discharged to Streams, January 2009.
3. Kolpin DW et al. Urban contributions of glyphosate and AMPA to streams in the United States. Sci Total Environ. 2006;354(2-3):191-197.
4. Beyond Pesticides. Denmark Restricts Water-Contaminating Herbicide, September 2003.
5. Richard S et al. Differential effects of glyphosate and Roundup on human placental cells. Environ Health Perspect. 2005;113(6):716-720.
6. United States EPA. Consumer Factsheet on Glyphosate, January 2008.
7. United States EPA. Method 547: Determination of glyphosate in drinking water by direct aqueous injection HPLC, 2008.