Glyphosate and Aminomethylphosphonic acid (AMPA) analysis in plants using LC-MS/MS

Significance of Topic

Glyphosate is the most widely applied herbicide globally and its main degradation product, aminomethylphosphonic acid (AMPA), is of growing regulatory and health concern. Reliable quantification of both compounds in plant tissues is crucial for environmental monitoring, food safety assessments and herbicide efficacy studies.

Study Objectives and Overview

The authors aimed to develop a direct, derivatization-free LC-MS/MS method for simultaneous determination of glyphosate and AMPA in plant matrices. The focus was on achieving low ppb sensitivity, robust calibration in clean and complex samples, and demonstration of matrix-matched and standard addition approaches.

Methodology and Instrumentation

This study employed reversed-phase liquid chromatography coupled to a Shimadzu LCMS-8060 triple quadrupole mass spectrometer operating in negative electrospray ionization mode. Key steps included:

• Chromatographic separation on a Bio-Rad Micro-Guard Cation H+ Cartridge with a ternary mobile phase (formic acid in water, acetonitrile, phosphoric acid in water) and a divert valve to minimize system contamination.
• MRM transitions optimized for glyphosate (168.1>62.9 and 168.1>78.9) and AMPA (110.0>79.0 and 110.0>63.0) using LabSolutions software.
• Source gases and temperatures set to enhance desolvation and ion transmission.
• Sample preparation involving grinding of barley and lemongrass, extraction with 0.1% formic acid, filtration and direct injection.
• Calibration strategies: external six-point curves (0.1–10 ppb), matrix-matched calibration in glyphosate-free lemongrass, and standard addition in glyphosate-containing barley.

Main Results and Discussion

Analysis of neat standards yielded sharp chromatographic peaks at the lower limit of quantitation (0.1 ppb) and the upper limit (10 ppb). Linearity was excellent with r2 values of 0.9999 for glyphosate and 0.9997 for AMPA. In lemongrass matrix, linearity remained strong down to 0.1 ppb (r2 > 0.993) despite the absence of cleanup. Standard addition in barley demonstrated accurate quantitation of endogenous glyphosate (1.084 ppb) and AMPA (0.235 ppb) with r2 > 0.997.

Benefits and Practical Applications

The method offers:

• Direct analysis without derivatization, reducing sample handling and potential artifacts.
• Sub-ppb sensitivity suitable for trace-level monitoring.
• Flexible calibration strategies to accommodate both glyphosate-free and contaminated samples.
• High throughput compatible with routine quality control and research workflows.

Future Trends and Potential Utilization

Expanding this methodology to include additional herbicides or polar metabolites could enable comprehensive residue profiling in crops. Advances in column chemistries and ion-mobility separations may further enhance selectivity. Coupling with high-resolution mass spectrometry could support non-target screening of emerging contaminants.

Conclusion

This work validates a robust LC-MS/MS approach for simultaneous quantitation of glyphosate and AMPA in plant tissues at trace levels. The Shimadzu LCMS-8060 platform demonstrated exceptional sensitivity, linearity and adaptability to complex matrices, making it a valuable tool for environmental, food safety and agronomic studies.

Instrumentation Used

• Shimadzu LCMS-8060 triple quadrupole mass spectrometer
• Bio-Rad Micro-Guard Cation H+ Cartridge (30 × 4.6 mm)

References

• Niemann L., et al. A critical review of glyphosate findings in human urine samples and comparison with the exposure of operators and consumers. Journal für Verbraucherschutz und Lebensmittelsicherheit 10(1):3–12 (2015).