Paraquat, Diquat, and Mepiquat Analysis in Environmental Water - An Agilent SampliQ WCX SPE and LC/MS/MS Method

Significance of the Topic

The quaternary ammonium herbicides paraquat diquat and mepiquat are extensively used in agriculture and subject to strict regulation due to their environmental and health risks Further a robust analytical approach is needed to overcome challenges posed by their high polarity and cationic nature ensuring reliable monitoring in water samples

Study Objectives and Overview

This study presents a streamlined workflow combining Agilent SampliQ WCX solid phase extraction and LC MS MS analysis with an InfinityLab Poroshell 120 HILIC Z column for simultaneous determination of these herbicides in environmental water

Instrumentation Used

• Agilent 1290 Infinity II liquid chromatograph
• Agilent 6470A triple quadrupole mass spectrometer with Jet Stream ESI source
• Agilent InfinityLab Poroshell 120 HILIC Z column 2.1×100 mm 2.7 µm
• Agilent SampliQ WCX SPE cartridges 3 mL 60 mg
• PTFE 0.2 µm syringe filters and Vac Elut manifold

Methodology

Environmental water from a local lake was filtered then spiked with EDTA to complex metal ions and adjusted to pH 7 Solid phase extraction on a WCX cartridge involved conditioning with methanol and water loading of the sample washing with phosphate buffer and methanol and elution with methanol water formic acid The LC method used a gradient from high organic to more aqueous conditions with mobile phase A 50 mM ammonium formate pH 3 and B 0 1% formic acid in acetonitrile at 0 5 mL/min Column temperature was 35 °C and injection volume was 1 µL or 5 µL for enhanced sensitivity MS detection was performed in positive mode monitoring characteristic ion transitions for mepiquat diquat paraquat and their isotope labeled standards

Main Results and Discussion

Calibration was linear over 0 05 to 50 µg/L (0 01 to 50 µg/L for mepiquat) with R2 between 0 993 and 0 999 Recovery ranged from 83 6 to 112 7% and RSD was below 9 6% Chromatograms demonstrated sharp peak shapes and baseline separation Low level detection at 0 01 µg/L was achieved for paraquat and diquat using a 5 µL injection without compromising performance

Benefits and Practical Applications

• Efficient simultaneous extraction and analysis of multiple cationic herbicides
• High sensitivity and selectivity suitable for trace level monitoring
• Robust SPE cleanup reducing matrix interferences
• Short analysis time enabling high sample throughput
• Applicability to routine environmental monitoring and regulatory compliance

Future Trends and Potential Applications

• Development of novel SPE sorbents for enhanced selectivity
• Miniaturization and automation of sample preparation and analysis
• Integration with high resolution mass spectrometry for broader screening
• Expansion to multi residue assays covering diverse environmental contaminants
• Portable and field deployable systems for on site monitoring

Conclusion

The combination of Agilent SampliQ WCX SPE and LC MS MS on an InfinityLab Poroshell HILIC Z column provides a reliable sensitive and efficient method for trace analysis of paraquat diquat and mepiquat in environmental water demonstrating excellent validation metrics and suitability for routine monitoring

References

• US Environmental Protection Agency Method 549 2 Determination of Diquat and Paraquat in Drinking Water by Liquid Solid Extraction and High Performance Liquid Chromatography with Ultraviolet Detection Revision 1 0 Cincinnati OH 1997