Trace level determination of Amitrole in Surface and Ground Water by Direct Aqueous Injection on the Agilent 6495 LC/MS/MS

Importance of the Topic

Amitrole is a widely used triazole herbicide that persists in water due to high solubility and low organic adsorption. Monitoring at sub-µg/L levels is essential for environmental safety and regulatory compliance in drinking water production, particularly for the toxic triazole metabolite 1,2,4-triazole.

Objectives and Study Overview

The study aims to develop and validate a sensitive direct aqueous injection LC/MS/MS method for trace quantification of Amitrole in surface and ground water. Using only 100 µL of unprocessed sample, the work demonstrates detection limits down to 0.001 µg/L suitable for routine compliance monitoring.

Instrumentation Used

The system comprises an Agilent 1290 Infinity UHPLC (bin pump, thermostat, autosampler, column oven) coupled to an Agilent 6495 triple quadrupole mass spectrometer with positive electrospray ionization. A Porous Graphite Carbon column (100 × 2.1 mm, 5 µm) was employed. Mobile phases were water and methanol, each containing 0.1% formic acid. 15N-labeled Amitrole served as an internal standard.

Methodology

A 100 µL aliquot of sample was injected directly. Chromatographic separation used a gradient from 100% aqueous to 100% organic over a short runtime. Multiple reaction monitoring transitions were set to m/z 85→43 for Amitrole and m/z 86→43 for the internal standard, both at 33 eV collision energy.

Results and Discussion

The method achieved a limit of quantitation of 0.001 µg/L with an RSD of 9.2% at this level and 2.4% at 0.02 µg/L. Calibration was linear between 0.001 and 0.5 µg/L. Replicate overlays demonstrated excellent reproducibility and sensitivity in surface water matrices.

Benefits and Practical Applications

• Eliminates laborious sample preparation, speeding analysis and reducing contamination risk.
• High sensitivity meets stringent drinking water regulations.
• Applicable across diverse environmental water samples for routine monitoring.

Future Trends and Opportunities

Automation of direct injection workflows could enable continuous water quality monitoring. Expanding the approach to other highly polar pesticides and their metabolites will enhance environmental surveillance. Advances in MS technology may further improve throughput and analytical robustness.

Conclusion

The direct injection LC/MS/MS method on the Agilent 6495 platform provides a rapid, sensitive, and reliable solution for trace-level determination of Amitrole in environmental waters, facilitating compliance with regulatory standards without extensive sample preparation.