Dioxin 2019: Flexible Automated Sample Clean up of PCDD/Fs and PCBs

Significance of the Topic

The accurate analysis of dioxins (PCDD/Fs) and polychlorinated biphenyls (PCBs) in environmental and food matrices is critical due to their toxicological impact and regulatory limits worldwide. Automated and reliable sample clean-up methods reduce contamination risk, improve throughput and consistency, and support compliance with EU and EPA protocols.

Objectives and Study Overview

This work presents the development and evaluation of the DEXTech automated sample clean-up system designed for rapid, high-throughput processing of diverse sample types, focusing on fish and corn oil matrices. Key objectives include:

• Comparing multiple DEXTech clean-up methods (Pure, Plus, Dioxin-only, PCB-only)
• Assessing recovery rates for 13C-labelled internal standards
• Demonstrating integration with downstream evaporation and GC-HRMS analysis

Methodology and Instrumentation

The sample preparation workflow comprises:

1. Dissolution of 5 g oil in n-hexane with addition of 13C standards
2. Automated clean-up using DEXTech Pure system with click-in column tower featuring acidic silica, alumina, activated carbon or Florisil variants
3. Electric column locking and unattended processing of up to 16 samples
4. Evaporation using the D-EVA vacuum centrifuge with cold trap and sensor-controlled down to target volumes
5. Reconstitution in injection solvent and analysis by GC-HRMS on a Thermo Fisher DFS system

Key instrumentation:

• DEXTech Pure automated clean-up platform
• DEXTech D-EVA vacuum centrifuge
• Thermo Fisher GC-HRMS (DFS) system

Main Results and Discussion

Comparative recovery studies in corn and fish oil demonstrated:

• Pure and Plus methods achieved over 70 percent recoveries for PCDD/Fs and PCBs
• Dioxin-only and PCB-only protocols offered cost-effective alternatives with selective fractionation
• Reproducible performance across multiple oil types

Fast processing of 16 samples in parallel reduced hands-on time and minimized cross-contamination risks.

Benefits and Practical Applications

The automated DEXTech workflow provides:

• High throughput and reduced cost per sample
• Compliance with EU and EPA official methods
• Enhanced reproducibility through electric column locking and automated loading
• Flexible fractionation schemes to match specific analytical goals

Future Trends and Opportunities

Potential developments include:

• Extension to PCB 209 and expanded congener separation
• Incorporation of polychlorinated naphthalenes and HBCDD analyses
• Adaptation for lower tolerated weekly intakes requiring larger sample loads

Conclusion

The DEXTech system offers a versatile, fully automated solution for PCDD/F and PCB clean-up, combining effective recovery, regulatory compliance, and operational efficiency. Its modular design and expandable methods suit a wide range of laboratory needs.