Confirmation of Low Level Dioxins and Furans in Dirty Matrix Samples using High Resolution GC/MS

Importance of the Topic

Over the past decades, human exposure to dioxins and dioxin-like compounds has steadily declined, yet these persistent pollutants remain a significant concern due to their toxicity and ubiquity in food chains. Reliable confirmation of trace levels in complex or "dirty" matrices, such as blood or fatty foods, is critical for regulatory compliance and risk assessment. High-resolution gas chromatography coupled with high-resolution mass spectrometry (HRGC/HRMS) has become the gold standard for these analyses.

Aims and Study Overview

This application note by Thermo Fisher Scientific describes the use of the DFS HRGC/HRMS system to detect and confirm femtogram-level dioxins and furans in challenging matrices. The objectives were to demonstrate sensitivity, selectivity, long-term stability, and regulatory compliance using standard reference materials and real-world blood extracts.

Methodology and Instrumentation

All experiments employed a Thermo Scientific DFS high-resolution mass spectrometer coupled to a TRACE GC Ultra with TriPlus Autosampler. Key parameters included:

• Column: TRACE TR-5MS, 60 m × 0.25 mm × 0.1 µm
• Injector: Splitless with hot-needle technique at 260 °C
• Oven Program: 120 °C hold, gradient to 210 °C, then to 275 °C, and final ramp to 300 °C
• Carrier Gas Flow: 0.8 mL/min
• Mass Spectrometer: EI positive mode, 48 eV electron energy, resolution 10 000 (10% valley)
• MID Setup: Five time windows covering tetra- to octa-PCDD/F congeners, using FC43 as lock and calibration compound

The multiple ion detection (MID) approach employed one quantification mass and one ratio mass per congener, with continuous mass calibration to ensure precision. FC43 was chosen over PFK due to lower boiling point and reduced source contamination.

Main Results and Discussion

Two experimental series were performed:

1. Seventy-two consecutive injections of a 17 fg/µL 2,3,7,8-TCDD standard to assess reproducibility and sensitivity.
2. Analysis of a pooled human blood extract spiked to 20 fg/µL 2,3,7,8-TCDD to test performance in a complex matrix.

Key findings:

• Signal-to-noise ratios exceeded 500:1 for 20 fg/µL TCDD on the 60 m column.
• Confirmation ion ratios remained within ±15% of expected values, meeting EPA Method 1613 Rev. B criteria.
• Chromatographic separation of PCDD/F congeners was robust, with baseline resolution even for closely eluting isomers.
• The DFS system demonstrated excellent stability and reproducibility across extended sequences, with no significant drift in mass calibration.

Benefits and Practical Applications

HRGC/HRMS using the DFS platform offers:

• Ultra-trace detection capability down to single-digit femtograms.
• High selectivity and specificity for unambiguous confirmation of target analytes.
• Robustness in dirty matrices, reducing false positives and ensuring regulatory compliance.
• Efficient sample throughput with minimal discrimination of higher-boiling congeners via hot-needle injection.

These advantages make it ideal for food safety monitoring, environmental surveillance, and biomonitoring studies.

Future Trends and Applications

Continued development is expected in:

• Further lowering detection limits through enhanced ion optics and source designs.
• Automated data processing workflows driven by machine learning for rapid confirmation.
• Expanded use of isotope-labeled standards for comprehensive congener coverage.
• Integration with high-speed sample preparation techniques to boost laboratory throughput.

Conclusion

The Thermo Scientific DFS HRGC/HRMS system reliably confirms femtogram-level dioxins and furans in complex matrices, fulfilling the most demanding regulatory requirements. Its exceptional sensitivity, selectivity, and robustness support routine analysis in food, environmental, and biological laboratories.

References

1. Lorber M. A pharmacokinetic model for estimating exposure of Americans to dioxin-like compounds past, present, and future. Sci Total Environ. 2002;288:81–95.
2. US EPA. Exposure and Human Health Reassessment of 2,3,7,8-TCDD and Related Compounds. National Center for Environmental Assessment; 2000.
3. Council Directive 2006/13/EC. Amending Annexes I and II of Directive 2002/32/EC on undesirable substances in animal feed regarding dioxins and dioxin-like PCBs. Off J Eur Communities L32/44;2006.
4. Council Directive 96/23/EC. Performance of analytical methods and interpretation of results. Off J Eur Communities L221/8;2002.
5. Council Directive 2002/69/EC. Sampling and analysis methods for dioxins and dioxin-like PCBs in foodstuffs. Off J Eur Communities L209/5;2002.
6. Council Directive 2002/70/EC. Requirements for determination of dioxins and dioxin-like PCBs in feedingstuffs. Off J Eur Communities L209/15;2002.
7. US EPA Method 1613 Rev. B. Tetra-through Octa-Chlorinated Dioxins and Furans by Isotope Dilution HRGC/HRMS. Office of Water Engineering and Analysis Division;1994.
8. Patterson DG Jr., Welch SM, Focant J-F, Turner WE. Use of GC and MS techniques for human biomonitoring. Lecture, 26th Int. Symp. Halogenated Persistent Organic Pollutants; Oslo, Norway;21–25 Aug 2006.
9. Turner WE, Welch SM, DiPietro ES, et al. Instrumental approaches for improving detection limits for selected PCDD congeners as background levels decline. Poster, 26th Int. Symp. Halogenated POPs; Oslo, Norway;21–25 Aug 2006.