Polychlorinated dibenzo-p-dioxins/furans analysis in food and feed at regulatory limits using the Orbitrap Exploris GC S mass spectrometer

Polychlorinated dibenzo-p-dioxins/furans (PCDD/F) analysis in food and feed using the Orbitrap Exploris GC S mass spectrometer — application note summary

Significance of the topic

PCDD/Fs are highly toxic contaminants that require ultra-trace, regulatory-compliant monitoring in food and feed. Regulatory methods demand high sensitivity, accurate isotopic-dilution quantitation, and sufficient mass resolving power to avoid isobaric interferences. Historically, magnetic sector GC-HRMS instruments set the standard; this study evaluates a high-resolution, accurate-mass Orbitrap-based platform as a cost- and operator-effort-efficient alternative capable of meeting EU performance criteria.

Goals and overview of the study

The application note aims to demonstrate that the Thermo Scientific Orbitrap Exploris GC S mass spectrometer, equipped with the NeverVent Advanced Electron Ionization (AEI) source and paired with a tailored eWorkflow, can: deliver the sensitivity, selectivity and quantitative performance required by Commission Regulation (EU) 2017/644; achieve LOQs at or below 1/5 of maximum levels (MLs) for typical food and feed matrices; and agree with results obtained by magnetic sector GC-HRMS.

Methodology and sample preparation

Sample types: representative foods (butter, laying hen fat, sunflower and fish oils) and feed items (edible flowers, dill tips), plus laboratory control spikes.

Extraction and cleanup:

• Feed matrices: accelerated solvent extraction (Thermo Scientific Dionex ASE 350).
• Fatty matrices: sulfuric acid lipid degradation followed by hexane back-extraction.
• Automated multi-column cleanup (acidic silica, alumina, carbon) performed on DEXTech Plus system; first fraction (containing ortho-PCBs and PCDD/Fs) concentrated to 50 µL in nonane.
• Isotopic dilution using 13C-labeled internal standards; syringe standards (13C-TCDD and 13C-HxCDD) added prior to shipment. Calibration prepared from EN1948 isotopically labeled mixes in a six-point series spanning low fg/µL to several pg/µL levels for tetra- through octa-chlorinated congeners.

Instrumentation used

Chromatography and GC front end:

• Thermo Scientific TRACE 1610 GC with TraceGOLD TG-Dioxin Film capillary column (60 m × 0.25 mm I.D. × 0.25 µm).
• Thermo Scientific TriPlus RSH autosampler and iConnect-PTV large-volume injection (5 µL). Injection: splitless/PTV large-volume protocol with programmed temperature ramp.

Mass spectrometry and acquisition:

• Thermo Scientific Orbitrap Exploris GC S with NeverVent AEI source (source temp 350 °C), electron ionization (EI).
• High resolving power operation: 60,000 FWHM @ m/z 200, delivering sub-ppm mass accuracy (internal correction <1 ppm reported).
• Acquisition mode: timed-SIM (tSIM) for targeted congeners; isolation windows and lock masses applied for mass accuracy maintenance.
• Data system: Thermo Scientific Chromeleon CDS with preinstalled HRAM Dioxin eWorkflow v1.0 for automated method setup, isotopic-dilution quantitation templates, and interactive compliance review.

Main results and discussion

Sensitivity and calibration:

• Quantitation demonstrated down to 2 fg/µL (10 fg on-column, 5 µL injection). Check standards at 4 fg/µL (20 fg on-column) and 20 fg/µL (100 fg on-column) met the required uncertainty and response criteria.
• Linear calibration across congeners: correlation coefficients >0.999 and %RSD ≤2.25% for response factors.
• Ion ratio deviation and calibration response satisfied EU criteria: ion ratio within ±15% of theoretical and calibration/check responses within ±25% of average response factor (AvRF).

Mass selectivity and resolving power:

• EU 2017/644 requires mass resolution ≥10,000 (at 5% peak height) across the mass range to avoid isobaric interferences. OCDD (m/z 455.7401) was used to evaluate high-mass performance: simulation indicates ~23,000 resolution needed for compliance at that m/z.
• Orbitrap Exploris GC S operated at 60,000 (at m/z 200), which corresponds to approximately R ≈ 39,700–40,000 at OCDD — well above the required resolution, providing enhanced selectivity versus potential interferences.

Method performance on incurred matrices and comparison with GC-HRMS:

• Sample limits of quantification (LOQs, WHO-PCDD/F-TEQ pg/g) achieved: butter 0.229; laying hen fat 0.232; fish oil 0.232; edible flowers 0.062; dill tips 0.061. All food LOQs were below the 1/5 ML threshold required by EU 2017/644; feed items also met these levels.
• Comparative analysis with a Thermo Scientific DFS magnetic sector GC-HRMS (which injected a larger extract volume) showed good agreement at concentrations near and below regulatory limits, indicating the Orbitrap platform’s enhanced sensitivity can match established GC-HRMS results while using smaller injections.

Benefits and practical applications

• Regulatory compliance: meets EU performance metrics (sensitivity, mass resolution, ion ratio, calibration stability) for PCDD/F determination in food and feed.
• Operational advantages: Orbitrap-based HRAM offers high mass resolving power and sub-ppm accuracy with potentially lower cost and operational complexity than magnetic sector instruments.
• Workflow integration: Chromeleon CDS HRAM Dioxin eWorkflow simplifies method setup, isotopic-dilution quantitation, automated checks (ion ratios, AvRF deviations), and reporting—improving analyst throughput and auditability.

Future trends and potential applications

• Lower regulatory thresholds: the platform’s demonstrated sensitivity and selectivity position it to accommodate potential future tightening of MLs for feedstuffs and food matrices.
• Broader HRAM adoption: high-resolution accurate-mass Orbitrap technology may become a practical alternative for routine dioxin/PCB monitoring laboratories seeking reduced operational cost and simplified maintenance compared with magnetic sector HRMS.
• Extended target lists and non-target screening: the combination of high resolving power and accurate mass supports expansion to additional halogenated contaminants and improved retrospective analysis capability.

Conclusion

The application note demonstrates that the Orbitrap Exploris GC S mass spectrometer, paired with the NeverVent AEI source, iConnect-PTV large-volume injection, comprehensive sample cleanup, and the Chromeleon HRAM Dioxin eWorkflow, delivers the sensitivity, mass selectivity, and quantitative performance required by EU Regulation 2017/644 for PCDD/F analysis. Achieved LOQs across multiple food and feed matrices were below the 1/5 ML compliance threshold, calibration linearity and precision were excellent, and results agreed with magnetic-sector GC-HRMS data while using smaller injected sample amounts.

References

1. Commission Regulation (EU) 2017/664 (2017). Laying down method of sampling and analysis for the control of levels of dioxins, dioxin-like PCBs and no-dioxin-like PCBs in certain foodstuffs and repeal Regulation (EU) No. 589/2014.
2. Commission Regulation (EU) 2017/771 (2017). Amending Regulation (EC) no. 152/2009 as regards the methods for the determination of the levels of dioxins and polychlorinated biphenyls.
3. Commission Regulation (EU) 2023/915 of 25 April 2023 on maximum levels for certain contaminants in food and repealing Regulation (EC) No 1881/2006.
4. Directive 2002/32/EC of the European Parliament and of the Council of 7 May 2002 on undesirable substances in animal feed.
5. World Trade Organization. (2023) Committee on Sanitary and Phytosanitary measures.