Sensitive Determination of dl- and ndl-PCBs in Foodstuffs and Animal Feed using the 7890A / 7000B GC-MS/MS System

Significance of the topic

Polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) are persistent, lipophilic environmental contaminants that bioaccumulate in the food chain and pose serious health risks even at low exposure levels. Routine, high-confidence monitoring of dioxin-like PCBs (dl-PCBs) and non-dioxin-like (ndl-PCB) indicators in food and animal feed is critical for food safety, regulatory compliance and public health protection.

Objectives and study overview

This collaborative study between the Chemical and Veterinary Analytical Institute Münsterland-Emscher-Lippe (CVUA-MEL) and Agilent Technologies aimed to:

• Assess the performance of GC-MS/MS in electron ionization mode as a sensitive screening and confirmatory method for dioxins and dl-PCBs in food and feed.
• Evaluate GC-MS/MS as a cost-effective alternative to GC-HRMS for official confirmatory analysis under EU regulation EC 1883/2006.
• Demonstrate reliable quantification of six indicator (ndl-) PCBs at levels proposed for harmonized maximum residue limits (MRLs) in feed (e.g., 10 ng/g).

Methodology and Instrumentation

Sample preparation involved exhaustive extraction of lipophilic analytes (Soxhlet or ASE), lipid removal with acid-coated silica, and multilayer clean-up including Florisil and activated carbon columns to separate PCDD/F, mono-ortho and non-ortho PCBs. Quantification of 17 WHO-listed 2,3,7,8-congeners and 12 dl-PCB congeners relied on isotopically labeled 13C internal standards and Toxic Equivalency Factors (TEFs) for TEQ calculation (WHO98 and WHO05 schemes).

Results and Discussion

Chromatographic separation of mono-ortho and non-ortho dl-PCBs and six indicator ndl-PCBs was achieved within 45 minutes. The Agilent 7890A/7000B GC-MS/MS system delivered:

• Low-picogram WHO-TEQ detection limits for individual dl-PCB congeners.
• Excellent linearity, reproducibility and EU method screening criteria compliance for both dl- and ndl-PCBs.
• TEQ results within ±10 % compared to GC-HRMS across 80 food/feed samples, with slightly higher sensitivity by HRMS at the lowest concentration range.
• Accurate quantification of Σ6 ndl-PCBs down to <1 ng/g, meeting the proposed MRLs for animal feed.

Benefits and Practical Applications

GC-MS/MS offers a reliable, faster and more cost-effective workflow than high-resolution mass spectrometry for routine confirmatory analysis of dioxins and PCBs in official food and feed control. The method supports EU regulatory requirements, including upper-bound and action-level monitoring, and simplifies TEQ calculation through robust isotope dilution calibration.

Used Instrumentation

• Agilent 7890A Gas Chromatograph
• Agilent 7000B Triple Quadrupole GC-MS/MS
• High-Resolution GC-MS system for method comparison

Future Trends and Opportunities

Further developments may include integration of ultra-high sensitivity mass analyzers, expansion to multiresidue screening of emerging persistent organic pollutants, automated sample handling and data processing, and on-site or portable GC-MS/MS systems for rapid field analysis.

Conclusion

The study demonstrates that GC-MS/MS in EI mode is a valid and efficient alternative for confirmatory determination of dl- and ndl-PCBs in food and feed, delivering comparable performance to GC-HRMS and fulfilling current and forthcoming EU regulatory requirements.