Non-Target and Post-Target Analysis of Emerging Halogenated Contaminants in American and European Eels

Importance of the Topic

Emerging halogenated contaminants accumulating in aquatic wildlife represent a growing ecological and human health concern. American and European eels (Anguilla sp.), both considered threatened or critically endangered, bioaccumulate persistent organic pollutants over their multi-year life cycle. Traditional target analysis often overlooks novel or non-legacy chemicals. High-resolution time-of-flight mass spectrometry (TOFMS) offers a comprehensive, non-target approach to uncover previously unidentified halogenated compounds and inform conservation and regulatory strategies.

Objectives and Study Overview

This study aimed to apply non-target and post-target TOFMS workflows to eel tissue extracts from multiple sampling sites across North America and Europe. The primary goal was to detect and tentatively identify lipophilic halogenated contaminants not covered by conventional monitoring, assess spatial contamination patterns, and evaluate the performance of a Pegasus GC-HRT platform for this purpose.

Methodology and Instrumentation

The workflow included:

• Sample collection: Juvenile eels from seven locations (e.g., Miramichi River, Hudson River, Lake Ontario, Canal Dessel-Schoten).
• Homogenization and extraction: Tissue homogenized and extracted with dichloromethane (DCM) or DCM/hexane (1:1).
• Cleanup: Gel permeation chromatography to remove lipids.
• Analysis: LECO Pegasus GC-HRT in electron ionization mode, full mass range m/z 45–1000, resolving power >25 000 at m/z 218.9, acquisition rates >200 spectra/s.
• Data processing: Spectral deconvolution and H/Cl scaled mass defect plots to highlight halogenated features.

Key Results and Discussion

Non-target analysis revealed both legacy and novel halogenated compounds:

• Legacy pollutants: Polychlorinated biphenyl fragments, DDT metabolites, chlorinated phenols.
• Newly detected compounds: Non-legacy chlorinated styrenes (hepta- and octachlorostyrene), brominated aromatics including pentabromobenzene, various siloxanes and alkanes.
• Spatial variability: Distinct contamination profiles observed among sites, notably elevated brominated aromatics in Miramichi samples versus PCB-dominated extracts from the Hudson River.
• Analytical performance: Mass accuracy within 1 ppm for base peak ions, demonstrating reliable molecular formula assignment.

Benefits and Practical Applications

The non-target TOFMS approach enables comprehensive screening of halogenated pollutants in biota, informing risk assessments and environmental monitoring. Rapid full-scan acquisition and high mass accuracy facilitate discovery of previously undetected contaminants, guiding future toxicological studies and regulatory priorities.

Future Trends and Applications

Further developments could include:

• Integration of suspect screening libraries to accelerate compound annotation.
• Quantitative methods for novel contaminants to assess bioaccumulation kinetics.
• Longitudinal monitoring to track temporal trends in contaminant loads.
• Expansion to other vulnerable species and matrices (sediment, water).

Conclusion

High-resolution TOFMS combined with H/Cl scaled mass defect plotting proved effective for non-target identification of both legacy and emerging halogenated contaminants in eel tissues. The study highlights diverse spatial contamination patterns and underlines the potential of advanced mass spectrometric workflows to enhance environmental contaminant surveillance.

References

1. Dekker W. Fisheries 2003, 28(12), 28–30.