Multi-residue analysis of pyrethroids in soil and sediment using QuEChERS by LC/MS/MS

Importance of the Topic

Pyrethroid insecticides are widely employed in agricultural and urban settings due to their high efficacy against target pests and low acute toxicity to humans. Their low water solubility and strong adsorption to particles cause accumulation in soil and sediment, posing risks to non-target organisms and ecosystem health. Reliable multi-residue methods are essential for monitoring pyrethroids at trace levels and ensuring environmental safety.

Objectives and Study Overview

This work aims to develop and validate a QuEChERS-based sample preparation coupled with high-speed LC/MS/MS for simultaneous quantification of 14 pyrethroid compounds in soil and sediment. The study evaluates extraction efficiency, matrix effects, method sensitivity, and real-world applicability by analyzing field samples from a residential garden and Lake Biwa sediment.

Methodology

Sample hydration and extraction follow the original QuEChERS approach with minor modifications. A typical procedure involves:

• Weighing 5 g of soil or 10 g of sediment and hydrating with 5 mL water
• Adding 10 mL acetonitrile and a salt mixture (MgSO₄, NaCl, trisodium citrate, disodium hydrogencitrate)
• Vigorous shaking for 1 min and centrifugation to obtain the acetonitrile extract
• Cleanup by dispersive SPE using MgSO₄, PSA, and GCB followed by filtration

Quantitative LC/MS/MS analysis employs a pentafluorophenyl column with a methanol/ammonium acetate gradient and an ESI source in positive/negative switching mode. Multiple reaction monitoring (MRM) transitions were optimized for each analyte.

Used Instrumentation

• UHPLC System: Shimadzu Nexera
• Column: Kinetex 2.6 µm PFP 100 Å, 100 × 2.1 mm
• Mass Spectrometer: Shimadzu LCMS-8050 triple quadrupole with ultra-fast scanning and polarity switching

Main Results and Discussion

All 14 pyrethroids except tefluthrin were efficiently ionized and separated by LC/MS/MS. Calibration curves exhibited excellent linearity (r² > 0.997) over wide concentration ranges (0.01–500 µg/L). Method detection limits reached low ppt levels for key analytes such as fenpropathrin, permethrin, bifenthrin, and silafluofen. Recovery tests in soil and sediment matrices yielded 70–120 % with negligible matrix effects, demonstrating robust quantitation. Analysis of real samples detected ethofenprox and permethrin in garden soil at concentrations near 0.01–0.03 ppb, while sediment samples showed no detectable residues.

Benefits and Practical Applications

• High sensitivity allows trace-level monitoring of multiple pyrethroids in complex matrices
• QuEChERS sample preparation provides rapid cleanup with minimal matrix interference
• Ultra-fast LC/MS/MS throughput supports high sample numbers in routine environmental testing and regulatory compliance

Future Trends and Potential Applications

Advances in high-resolution mass spectrometry and automated QuEChERS workflows could further enhance selectivity and reduce analysis time. Expansion of the method to cover degradation products and emerging semi-synthetic pyrethroids will be important for comprehensive environmental surveillance. Integration with field-deployable extraction kits may enable on-site screening.

Conclusion

A QuEChERS-based LC/MS/MS method was successfully established for simultaneous quantification of 14 pyrethroids in soil and sediment at sub-ppb levels. The approach offers high recovery, minimal matrix effects, and rapid analysis, proving suitable for environmental monitoring and quality control in agricultural and urban contexts.