Simultaneous Analysis of Pesticides in Environment Water using LC-MS

Significance of the Topic

Monitoring pesticide residues in environmental waters is critical for safeguarding ecosystems and human health. Regulatory agencies set stringent criteria for allowable pesticide concentrations, requiring analytical methods that combine high sensitivity, selectivity and throughput. A simultaneous LC-MS approach streamlines analysis of multiple compounds, reducing time and resource demands while ensuring compliance with water quality standards.

Objectives and Study Overview

This study aimed to establish a unified sample-preparation and LC-MS protocol capable of detecting 28 priority pesticides at one-hundredth of regulatory criteria levels. Key goals included optimizing solid-phase extraction, evaluating recoveries in different water matrices (ion-exchange, river and tap water) and demonstrating method robustness under real-world conditions.

Methodology and Sample Preparation

Water samples were spiked at 1/100 of the criteria concentrations and subjected to the following workflow:

• Add 0.25 g EDTA-2Na⋅2H2O to 500 mL sample; adjust pH to 3.5 with nitric acid (1+10).
• Sequentially pass through a divinyl benzene-N-vinyl pyrrolidone copolymer SPE column (500× concentration) and an activated carbon SPE column.
• Backflush-elute copolymer column with 5 mL acetonitrile; activate carbon column with 5 mL methanol.
• Evaporate under nitrogen to <100 μL, dilute to 1 mL, inject 10 μL into LC-MS.

Used Instrumentation

The analysis employed a Shimadzu LC-MS system configured as follows:

• Column: L-column ODS (150 mm × 2.1 mm I.D.) at 40 °C.
• Mobile phase A: 0.1% formic acid in water; mobile phase B: acetonitrile; gradient from 0% to 95% B over 40 min.
• Flow rate: 0.2 mL/min; injection: 10 μL.
• ESI source (positive/negative) with probe voltage ±4.5/–3.5 kV; CDL at 250 °C; block heater at 200 °C; drying gas 1.5 L/min; nebulizing gas pressure 0.2 MPa.
• Data acquisition by selected-ion monitoring (SIM) targeting specific m/z for each pesticide.

Main Results and Discussion

Recovery data showed:

• Ion-exchange water: 25 of 27 target pesticides recovered at 81–139% with copolymer SPE; dalapon (5%) and acephate (8%) were exceptions.
• River water: Slightly elevated baselines and minor interferences, but clear SIM peaks and recoveries of 62–133% for most analytes.
• Tap water: Good performance for most compounds; poorer recoveries for thiram and asulam likely due to chlorine interactions.

Sensitivity enabled detection at 1/100 of criteria values. Benomyl and benfuracarb degraded in aqueous solution to MBC and carbofuran, respectively, but were quantified reliably.

Benefits and Practical Applications

This simultaneous LC-MS method offers:

• High throughput screening of up to 28 pesticides in a single run.
• Robust SPE protocol adaptable to diverse water matrices.
• Compliance support for regulatory monitoring and QA/QC programs.
• Reduced solvent use and labor compared with individual analyses.

Future Trends and Applications

Emerging directions include expanding compound coverage, integrating automated SPE and UHPLC-MS to further shorten cycle times, exploring novel sorbent materials for improved extraction, and applying machine-learning algorithms to enhance data processing and anomaly detection. Coupling this workflow with mobile or field-deployable MS platforms could enable near-real-time water quality surveillance.

Conclusion

A validated SPE-LC-MS protocol was successfully developed for simultaneous determination of 28 pesticides at 1/100 regulatory levels in ion-exchange, river and tap water. The method delivers sufficient sensitivity, acceptable recoveries and operational simplicity, making it well suited for routine environmental monitoring and compliance testing.

References

• Shimadzu Application News No. C34, “Simultaneous Analysis of Pesticides in Environmental Water Using LC-MS”, Shimadzu Corporation.
• Shimadzu Application News No. C33, Shimadzu Corporation.