Orbitrap Exploris GC mass spectrometer performance- based analysis of polychlorinated dibenzo-p-dioxins/furans (PCDD/F)

Importance of the Topic

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) are highly toxic and persistent environmental pollutants regulated under global conventions. Their formation during thermal processes and stability in ecosystems pose ongoing risks to food chains and human health, driving the need for ultra-trace analytical methods to ensure regulatory compliance and safeguard public health.

Objectives and Study Overview

This technical note presents an evaluation of the Thermo Scientific™ Orbitrap Exploris™ GC mass spectrometer for the trace-level determination of PCDD/F in soil samples. It covers method optimization, performance assessment against EPA Method 1613 criteria, and demonstrates full compliance with regulatory limits using high-resolution accurate-mass (HRAM) measurements.

Methodology and Instrumentation

A six-point isotopic dilution calibration ranging from 0.05 to 100 pg/μL was prepared for EPA 1613 congeners. Two grams of soil were extracted with acetonitrile/hexane, centrifuged, and reconstituted in nonane with internal standards.

• Gas Chromatography: Thermo Scientific™ TRACE™ 1610 GC with TraceGOLD™ TG-Dioxin column (60 m × 0.25 mm × 0.25 μm), splitless injection (1.5 μL), 44.7 min run time.
• Mass Spectrometry: Orbitrap Exploris GC MS in timed-SIM mode, resolving power 60,000 FWHM at m/z 200, electron energy optimized at 40 eV, transfer line at 300 °C, ion source at 350 °C, internal lock masses for sub-ppm accuracy.
• Data Processing: Chromeleon™ 7.3.1 CDS with Dioxin Analyzer workflow for automated quantification and performance checks.

Main Results and Discussion

Electron energy optimization between 30 and 70 eV identified 40 eV as optimal for minimizing fragmentation and maximizing ion yield, improving signal-to-noise for 2,3,7,8-TCDD at femtogram levels. Calibration curves exhibited linearity over three orders of magnitude with R² > 0.995 and RSD < 6%. Mass resolution for octachlorodibenzodioxin (OCDD) measured ~40,000 at 200 m/z, exceeding the 10,000 at 5% peak height required by EPA 1613. Repetitive analysis of a spiked soil extract demonstrated accurate quantitation at fg concentrations, with retention time, ion ratio, and relative response factors consistently meeting regulatory tolerances.

Benefits and Practical Applications

• Femtogram-level sensitivity for PCDD/F detection using minimal injection volume.
• High mass accuracy (< 5 ppm) and resolution ensure unambiguous congener identification.
• Integrated Chromeleon workflow simplifies compliance with EPA 1613 performance criteria.
• Reduced analysis time without compromising chromatographic resolution.
• Capability for retrospective data mining via full-scan HRAM acquisition.

Future Trends and Potential Applications

Advancements in HRAM GC-MS will facilitate non-targeted screening for emerging pollutants, enabling retrospective analysis of full-scan data to identify unknown chlorinated compounds. Integration with high-throughput sample preparation and data analytics will expand environmental monitoring, food safety, and industrial quality control applications.

Conclusion

The Orbitrap Exploris GC mass spectrometer delivers robust, high-resolution, accurate-mass analysis of PCDD/F at femtogram levels, fully complying with EPA Method 1613. Its optimized ion source parameters, automated data processing, and flexible acquisition modes make it a valuable tool for environmental laboratories requiring both targeted quantitation and non-targeted screening capabilities.

References

1. European Union Commission Regulation 2022/2002 Amending Regulation (EC) No 1881/2006 on maximum levels of dioxins and dioxin-like PCBs in foodstuffs. October 21, 2022.
2. United States Environmental Protection Agency Method 1613 Revision B: Tetra-Through Octa-Chlorinated Dioxins and Furans by Isotope Dilution HRGC/HRMS. EPA 821-B-94-005, 1994.
3. Warner N. A., Ladak A., Cavagnino D., Kutscher D. Thermo Scientific Technical Note 001594: Uncompromised sensitivity in polychlorinated dibenzo-p-dioxins/furans analysis using triple quadrupole GC-MS with cost-effective helium-saving technology. 2022.