The Importance of Autosampler Vial Selection in the GC-MS Analysis of Pyrethroid Pesticides at Low Concentration

Significance of the Topic

Monitoring trace levels of pyrethroid pesticides is critical for environmental and public health protection. These compounds can adsorb onto container surfaces, leading to inaccurate quantification at nanogram-per-milliliter concentrations. Selecting the right autosampler vial material is therefore essential to minimize analyte loss and ensure reliable GC-MS analysis.

Objectives and Study Overview

This work aimed to evaluate the impact of different vial types on the recovery and linearity of four pyrethroids (bifenthrin, permethrin isomers, cyfluthrin, cypermethrin) at 0.10 ng/mL in water. Three vial materials—non-silanized amber glass, polypropylene plastic, and high-purity clear neutral borosilicate glass—were compared using a solid‐phase extraction (SPE) pre-concentration followed by GC-MS with a programmable temperature vaporizer (PTV) simulated on-column injection.

Methodology

• SPE Extraction: HyperSep C18 cartridges (2000 mg/15 mL) conditioned with ethyl acetate, acetone, and water. One liter of spiked water passed under vacuum, washed with water, dried, then eluted with ethyl acetate. Eluent evaporated and reconstituted in 100 µL ethyl acetate, with 10 µL internal standard added.
• Calibration: Standards prepared in ethyl acetate at 50–2000 ng/mL, 100 µL aliquots mixed with 10 µL of 10 µg/mL internal standard in autosampler vials.
• GC-MS Analysis: PTV simulated on-column injection in splitless mode, SIM acquisition for targeted ions.

Used Instrumentation

• Solid-Phase Extraction: Thermo Scientific HyperSep C18 SPE cartridges
• Gas Chromatograph: Thermo Scientific TRACE GC Ultra with TraceGOLD TG-5SilMS column and GuardGOLD pre-column
• Autosampler: Thermo Scientific TriPlus RSH
• Mass Spectrometer: Thermo Scientific ISQ with EI ionization at 70 eV

Results and Discussion

Non-silanized amber glass vials showed poor recoveries (49–62%) and non-linear calibration due to iron oxide leaching and increased surface activity. Polypropylene vials improved linearity and recoveries (85–117%) but risked leachable organic contaminants when exposed to organic solvents. High-purity clear neutral borosilicate glass vials delivered the best performance, with recoveries of 81–117%, RSDs below 12%, and calibration coefficients (R²) above 0.99. Total ion chromatograms confirmed clean separation of isomeric mixtures down to 0.10 ng/mL after SPE pre-concentration.

Benefits and Practical Applications

• High-purity borosilicate vials prevent adsorption and extend analyte stability, supporting accurate trace pesticide monitoring.
• SPE coupled with PTV GC-MS provides low detection limits and robust quantification for environmental water testing.
• Optimized vial selection reduces re-analysis and improves laboratory throughput in QA/QC workflows.

Future Trends and Opportunities

Advances in low-adsorption materials and inert vial coatings will further reduce analyte loss. Automated SPE-GC-MS platforms with integrated vial selection protocols can streamline analysis of emerging contaminants. Combining high-resolution MS and novel sample containers may enable sub-ppt detection of ultra-trace organic pollutants.

Conclusion

Choosing a high-purity clear neutral borosilicate glass autosampler vial is crucial for reliable GC-MS quantification of low-level pyrethroids. The SPE-GC-MS workflow demonstrated excellent linearity, precision, and recovery at 0.10 ng/mL, supporting sensitive environmental monitoring and regulatory compliance.

References

1. Brian W. King and Anila I. Khan. The 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. Bernard H. W. S. De Jong et al. Glass, 1: Fundamentals. Ullmann’s Encyclopedia of Industrial Chemistry, Wiley-VCH, DOI:10.1002/14356007.a12_365.pub3.
3. ISO 719:1985. Glass – Hydrolytic Resistance of Glass Grains at 98 °C – Method of Test and Classification.