Organochlorine pesticides in eel

Importance of Organochlorine Pesticide Analysis in Eel

Organochlorine pesticides (OCPs) are persistent, bioaccumulative compounds that pose significant ecological and human health risks. Monitoring their levels in aquatic organisms like eel provides critical insight into environmental contamination, food chain transfer and regulatory compliance. Advanced separation and detection methods ensure accurate residue profiling and support risk assessment in fisheries and water quality management.

Objectives and Study Overview

This application note evaluates the performance of a fused-silica capillary column coated with CP-Sil 19 CB for the simultaneous separation and detection of 21 OCP residues in eel tissue. The study aims to:

• Optimize a temperature program and chromatographic conditions to resolve critical isomers (e.g., oxychlordane vs. heptachlor epoxide).
• Demonstrate reproducible analysis of eel extracts from North Sea and inland Dutch waters.
• Quantify environmental contamination levels near a known waste-dumping site.

Methodology and Applied Instrumentation

Sample Preparation:

• Soxhlet extraction of homogenized eel tissue using n-pentane.
• Alumina cleanup followed by silica fractionation into two portions to isolate target OCP fractions.

Applied Instrumentation:

• Gas Chromatograph with capillary injection (Grob mode, 1 µL, splitter opened after 0.5 min).
• Column: Agilent CP-Sil 19 CB, 0.22 mm × 16 m, 0.2 µm film thickness.
• Carrier Gas: Helium.
• Oven Program: 80 °C hold 3 min → ramp 35 °C/min to 150 °C (hold 2 min) → ramp 3 °C/min to 216 °C.
• Detector: Electron Capture Detector (ECD).

Main Results and Discussion

The optimized temperature program achieved baseline resolution of 21 OCPs, including challenging pairs such as oxychlordane and heptachlor epoxide. Key findings include:

• Retention times ranged from ~11 min (HCB) to ~31 min (p,p′-DDT).
• Relative retention indices confirmed consistent elution order against dieldrin.
• Eels sampled in the Hollandse IJssel near Gouderak exhibited exceptionally high residues: dieldrin (1.1 mg/kg) and endrin (0.18 mg/kg).
• Measured levels of cis-chlordane (0.019 mg/kg), trans-nonachlor (0.022 mg/kg) and oxychlordane (0.024 mg/kg) exceeded values observed in other Dutch inland waters.

The CP-Sil 19 CB phase outperformed conventional nonpolar columns (CP-Sil 5, 7, 8) by fully resolving critical isomeric pairs and maintaining separation efficiency over 25 sequential extracts.

Benefits and Practical Applications

Implementing this method offers:

• Comprehensive, high-throughput screening of OCPs in fish tissue for environmental monitoring.
• Enhanced resolution of problematic isomers without dual-column analyses.
• Reliability and reproducibility for routine QA/QC in environmental and food safety laboratories.

Future Trends and Opportunities

Continued development may focus on:

• Integration with tandem mass spectrometry (GC-MS/MS) for lower detection limits and confirmatory analysis.
• Adoption of faster temperature programming and shorter columns to reduce analysis time.
• Extension to other matrices (sediment, biota) to broaden environmental surveillance.
• Automation of sample cleanup (e.g., online SPE) to streamline workflows.

Conclusion

The use of an Agilent CP-Sil 19 CB capillary column combined with an optimized temperature program and ECD detection enables complete separation of 21 organochlorine pesticide residues in eel samples. This robust method delivers accurate quantitation of isomeric contaminants in challenging matrices and supports environmental monitoring and regulatory compliance.

References

1. Agilent Technologies, Inc. Application Note A00055, Organochlorine Pesticides in Eel, 2010.
2. Kerkhoff, M. A. T.; Otte, P. F. Netherlands Institute for Fishery Investigations.