Analysis of Acid Herbicides in Drinking and Surface Water Using On-line SPE-LC-MS/MS

Importance of the Topic

The presence of acidic herbicides in drinking and surface waters poses risks to human health and aquatic ecosystems. Sensitive and reliable analytical methods are essential to monitor these compounds at trace levels and ensure regulatory compliance.

Objectives and Study Overview

This work presents a fully automated on-line solid phase extraction coupled to liquid chromatography tandem mass spectrometry method for rapid extraction and quantification of sixteen common acid herbicides in various water matrices.

Methodology

Water samples of one to ten milliliters were acidified and spiked with isotope labelled internal standards before direct injection onto an ISOLUTE ENV+ on-line SPE cartridge. After trapping, analytes were backflushed onto a C18 analytical column using a gradient of dilute formic acid and acetonitrile. Quantitation was performed by multiple reaction monitoring with polarity switching and optimised transitions for each herbicide.

Instrumentation Used

• Agilent 1200 series high performance liquid chromatograph with binary pumps and switching valve
• ISOLUTE ENV+ on-line SPE cartridge (30 mm by 2.1 mm)
• Zorbax Eclipse Plus C18 column (2.1 mm by 100 mm, 1.8 micrometre)
• Agilent 6490 triple quadrupole mass spectrometer with ifunnel electrospray source

Main Results and Discussion

Calibration over a range of zero to 150 nanograms per litre showed quadratic fits with correlation coefficients above 0.999 for all compounds. Limits of detection were in the low nanogram per litre range. Recovery studies across soft, medium, hard and surface water matrices yielded values from 93 to 106 percent. Precision, expressed as relative standard deviation, remained below fifteen percent and trueness was within plus minus seven percent. No sample carryover was observed in randomized batches.

Benefits and Practical Applications

The on-line SPE LC MS MS approach streamlines sample preparation, reduces solvent consumption, increases laboratory throughput and maintains high accuracy and repeatability. It is well suited for routine monitoring of trace herbicides in environmental and drinking water quality programs.

Future Trends and Opportunities

Future developments may include extending the platform to additional polar organic contaminants, coupling with high resolution mass spectrometry for non target analysis and adaptation to portable or field deployable systems for real time monitoring of water quality.

Conclusion

The automated on-line SPE LC MS MS method provides a robust, sensitive and high throughput solution for accurate quantification of a broad spectrum of acid herbicides in drinking and surface waters. Its performance and low environmental footprint support regulatory compliance and environmental risk assessment.