Analysis of Low Level Pyrethroid Pesticides in Water

Importance of the Topic

Pyrethroid pesticides are widely used for domestic insect control but pose risks to aquatic organisms and human health at trace levels. Monitoring ultra-low concentrations in water is critical for environmental safety and public health.

Study Objectives and Overview

This study aimed to develop and validate a sensitive method for detecting five common pyrethroids in water at concentrations as low as 0.02 and 0.10 ng/mL. The approach combined solid-phase extraction for sample preconcentration and gas chromatography–mass spectrometry with a programmable temperature vaporizer for analysis.

Methodology

• Sample Preparation and SPE Extraction
  1 L water samples spiked with pyrethroids were passed through C18 SPE cartridges after conditioning with solvents. Cartridges were washed and analytes eluted with ethyl acetate. Eluates were dried, reconstituted to 100 µL, and internal standard added.
• Calibration Standards
  Calibration curves were prepared in ethyl acetate at 50–2000 ng/mL with an internal standard of 1,2,3,4-tetrachloronaphthalene.
• Chromatographic Separation and Detection
  Analysis was performed on a Trace GC Ultra with a TG-5SilMS column. Helium carrier gas at 1.2 mL/min, temperature program from 80 to 320 °C, and PTV simulated on-column injection in splitless mode. Detection used an ISQ mass spectrometer in EI mode with selected ion monitoring.

Instrumentation Used

• Thermo Scientific TRACE GC Ultra gas chromatograph
• TraceGOLD TG-5SilMS column with GuardGOLD pre-column
• TriPlus RSH Autosampler with programmable temperature vaporizer
• ISQ Mass Spectrometer operating in EI and SIM modes

Main Results and Discussion

The method exhibited linearity across 50–2000 ng/mL with R2 values above 0.995 for all pyrethroids. Recoveries ranged from 71% to 111% at 0.02 ng/mL and 82% to 111% at 0.10 ng/mL with RSDs below 22%. Using plastic vials minimized adsorption losses. The TraceGOLD column provided low bleed and resolved isomeric mixtures, enhancing sensitivity.

Benefits and Practical Applications

• High sensitivity and low detection limits suitable for environmental water monitoring
• Robust linearity and acceptable precision for routine analysis
• Reduced analyte loss through optimized vial selection and column chemistry
• Applicability in environmental labs, QA/QC, and regulatory compliance testing

Future Trends and Potential Applications

Modern GC column materials and advanced PTV injection strategies will further lower detection thresholds. Integration with high-resolution MS and automation can improve throughput. The approach may extend to other hydrophobic contaminants in complex environmental matrices.

Conclusion

The developed SPE–GC/MS method reliably quantifies trace pyrethroid pesticides in water at sub-ng/mL levels. Key features include efficient extraction, selective chromatographic separation, and minimized adsorption. This protocol offers a valuable tool for environmental monitoring and regulatory analysis.

References

1. King BW, Khan AI. Effect of the autosampler vial’s glass surface on GC-MS analysis of pyrethroid pesticides at ppb levels. Thermo Fisher Scientific, Runcorn, UK. Poster PSCCS 0512 588.
2. Khan AI. Application Note 20642: The effect of the autosampler vial’s glass surface on GC-MS analysis of pyrethroid pesticides at low concentration. Thermo Fisher Scientific, Runcorn, UK.