Sensitive Detection of Pyrethroids in Surface Water and Sediment

Importance of the Topic

Monitoring synthetic pyrethroid insecticides in aquatic environments is essential due to their high toxicity to fish and aquatic organisms at ultra low concentrations. Sensitive analytical techniques are required to detect these compounds in surface water and sediment for environmental safety and regulatory compliance.

Objectives and Overview of the Study

The study aimed to develop a highly sensitive method for quantifying six common pyrethroids in water and sediment matrices. The approach integrates negative chemical ionization tandem mass spectrometry and capillary flow backflushing to achieve detection limits at parts per trillion levels.

Methodology and Instrumentation

• Sample Extraction for Water
  • Amber glass bottle collection with surrogate addition
  • Liquid-liquid extraction using dichloromethane with manual agitation
  • Drying over sodium sulfate and solvent exchange to isooctane
• Sample Extraction for Sediment
  • Pressurized Fluid Extraction with accelerated solvent extractor
  • Cleanup by gel permeation chromatography and Florisil fractionation
• Chromatographic and Mass Spectrometric Analysis
  • Gas chromatograph with multimode inlet and mid-column backflushing
  • Triple quadrupole mass analyzer in negative chemical ionization mode
  • Ammonia reagent gas, nitrogen collision gas, helium quench gas
  • Multiple reaction monitoring transitions selected for six pyrethroid analytes

Main Results and Discussion

The method delivered estimated method detection limits as low as 0.01 ng per liter in water and 0.03 ng per gram in sediment for deltamethrin. Instrument detection limits ranged from 0.001 to 0.05 micrograms per liter in isooctane. Calibration curves over 0.01 to 10 micrograms per liter exhibited excellent linearity with correlation coefficients above 0.997. The negative chemical ionization approach suppressed matrix interferences and improved selectivity compared to electron ionization and electron capture detection.

Benefits and Practical Applications of the Method

• Sub ppt and low ppb quantification of pyrethroids in complex matrices
• Reduced false positives and enhanced specificity for halogenated analytes
• Efficient sample throughput using automated extraction and cleanup
• Capability for routine monitoring of urban and agricultural water sources

Future Trends and Potential Applications

• Extension to broader classes of halogenated environmental contaminants
• Integration with high resolution mass spectrometry for non target screening
• Field deployable instruments with simplified workflows
• Advanced data processing with machine learning for pattern recognition

Conclusion

The negative chemical ionization tandem mass spectrometry method with capillary flow backflushing provides highly sensitive and selective detection of pyrethroids in water and sediment. It meets stringent environmental monitoring requirements and supports accurate risk assessment for aquatic ecosystems.

References

• Weston DP Holmes RW You J Lydy MJ Aquatic toxicity due to residential use of pyrethroid insecticides Environ Sci Technol 39 9778 9784 2005
• Mekebri Abdou Presentation at Bay Delta Science Conference 2010
• Mekebri B Crane G Blondina Oros RL Rocca JL Extraction and analysis methods for determination of pyrethroid insecticides in surface water sediments and biological tissues Bull Environ Contam Toxicol 80 455 460 2008
• Grob RL Barry EF Modern Practice of Gas Chromatography John Wiley Sons 4th ed 2004