Low level quantification of PCDD/Fs in animal feed using the Thermo Scientific TSQ 9000 triple quadrupole GC-MS/MS system with AEI source

Significance of the Topic

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are persistent organic pollutants that pose serious health risks. Regulatory frameworks in the EU set strict maximum and action levels for these toxins in animal feed. High sensitivity, selectivity, and robustness of analytical methods are critical to reliably quantify trace levels of PCDD/Fs and to ensure compliance in routine testing environments.

Objectives and Study Overview

This work aimed to demonstrate that the Thermo Scientific™ TSQ™ 9000 triple quadrupole GC-MS/MS system, equipped with an Advanced Electron Ionization (AEI) source, can deliver sensitive, selective, and regulation-compliant quantification of the 17 toxic PCDD/F congeners in feed samples. The goal was to meet EU requirements on ion ratio tolerances (±15%), response factor variation (RSD ≤30%), and method limits of quantitation (≤1/5 of maximum levels) under everyday laboratory conditions.

Methodology and Instrumentation

Sample Preparation

• Accelerated solvent extraction of feed and control samples.
• Multi-layer acidic silica column cleanup followed by automated PowerPrep™ system with ABN silica, basic alumina, and carbon cartridges.
• Final extract in nonane, 10 µL total volume.

Instrumental Analysis

• Gas chromatograph: Thermo Scientific™ TRACE™ 1310 with splitless inlet, TraceGOLD™ TG-Dioxin column (60 m × 0.25 mm, 0.25 µm).
• Autosampler: Thermo Scientific™ TriPlus™ RSH with bottom sensing.
• Mass spectrometer: Thermo Scientific™ TSQ™ 9000 with AEI source, operated in timed SRM mode, collision gas argon at 70 psi.
• Tune and calibration via PFTBA; data acquired and processed in Chromeleon™ CDS software.
• Calibration by isotope-dilution response factors over eight-point curves; limits of detection determined statistically (n=8), LOQs set at lowest calibration level meeting EU IR and RF criteria.

Main Results and Discussion

Chromatographic separation on the TG-Dioxin column achieved baseline resolution of critical congeners (e.g., 2,3,7,8-TCDD/F, HxCDD/F) in accordance with EU regulation. The instrument detection limit for 2,3,7,8-TCDD was 0.58 fg on-column; method LOQs ranged from 0.02 to 0.32 pg, corresponding to ≤1/5 of regulatory limits. Ion ratios for all congeners remained within ±15% across a two-day sequence of 63 injections; response factor RSDs fell between 1.8% and 7.3%. Matrix-adjusted LOQs allowed reliable quantitation in 20 g feed samples. Analysis of real and QC feed samples produced upper-bound WHO-TEQ results comfortably below 1/5 ML, with deviations from parallel GC-HRMS data within ±20%.

Benefits and Practical Applications

The TSQ 9000 GC-MS/MS with AEI source provides:

• Exceptional sensitivity enabling smaller sample sizes and lower detection thresholds.
• Robust performance for routine high-throughput feed analysis.
• Reliable compliance with EU confirmatory criteria (ion ratios, calibration stability).

Future Trends and Opportunities

Advances may include integration of automated data review via machine learning, expansion to multi-class POP analysis, miniaturized sampling interfaces for on-site testing, and higher-resolution SRM methods. Continuous improvements in source design and chromatography will support faster runs and broader analyte coverage.

Conclusion

The study confirms that the Thermo Scientific TSQ 9000 GC-MS/MS system with AEI source delivers the sensitivity, selectivity, and robustness required for EU-compliant quantification of PCDD/Fs in animal feed. Its performance supports reliable routine monitoring at trace levels well below regulatory thresholds.

References

• European Commission. Commission Regulation (EU) No 644/2017. Off. J. Eur. Union L 92:9–34.
• European Commission. Commission Regulation (EU) No 771/2017. Off. J. Eur. Union L 115:22–42.
• European Commission. Guidance Document on Estimation of LOD and LOQ for Measurements in the Field of Contaminants in Feed and Food. JRC, 2019.
• Directive 2002/32/EC of the European Parliament and of the Council on undesirable substances in animal feed. Off. J. Eur. Union L 140:10–21.
• EPA Method 1613B. Tetra- through Octa-Chlorinated Dioxins and Furans by Isotope Dilution HRGC/HRMS. US EPA, 1994.
• Rivera-Austrui J., et al. Journal of Chromatography A 1513 (2017) 245–249.
• Thermo Fisher Scientific. Application Note 10590: Low Level Quantification of PCDD/Fs in Animal Feed. 2018.
• Horwitz, W., & Albert, R. L. Journal of AOAC International 89 (2006) 1095–1109.
• FMS Inc. PowerPrep™ Automated Cleanup System User Guide. 2015.