Simultaneous Extraction of PAHs and PCBs from Environmental Samples Using Accelerated Solvent Extraction

Importance of the Topic

Polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) are persistent organic pollutants of high toxicity and carcinogenicity. Reliable and efficient extraction methods are essential for environmental monitoring of contaminated matrices such as biota and soil. Simultaneous extraction reduces solvent consumption, analysis time, and sample handling while meeting regulatory requirements.

Study Objectives and Overview

The study aimed to develop a single accelerated solvent extraction (ASE) protocol for concurrent isolation of PAHs and PCBs from mussel tissue and contaminated soil. Two ASE methods were evaluated: one at higher temperature (125 C) and one at lower temperature (100 C) with in-cell cleanup using acidic alumina, to compare extraction efficiency and extract cleanliness.

Methodology and Instrumentation

Sample preparation included spiking 5 g mussel tissue or soil reference material with PAH and PCB surrogates, mixing with diatomaceous earth, and loading into 66 mL stainless steel ASE cells containing glass fiber filters and acidic alumina.
Two extraction methods were applied:

• Method 1: 125 C, 10 MPa, 4 static cycles of 6 min with dichloromethane
• Method 2: 100 C, 10 MPa, 5 static cycles of 4 min with dichloromethane

Post-extraction cleanup bypassed gel permeation chromatography by retaining lipids on alumina. Extracts were solvent exchanged to hexane and concentrated for analysis by GC–MS (for PAHs) and GC–ECD (for PCBs). The core instrumentation comprised a Thermo Scientific Dionex ASE 350 extractor, GC–MS, GC–ECD systems, capillary columns, and a nitrogen evaporator.

Key Results and Discussion

Both methods achieved PAH and PCB recoveries within EPA limits across mussel and soil matrices. Method 1 provided slightly higher recoveries for high–molecular weight compounds but exhibited greater coextractable interferences, requiring frequent inlet maintenance. Method 2 significantly reduced coextractables with minimal impact on most recoveries, though recoveries of certain high–molecular weight PAHs and Aroclor 1254 declined modestly.

Benefits and Practical Applications

The optimized ASE approach offers:

• Simultaneous extraction of PAHs and PCBs in a single run
• Reduced solvent usage and extraction time compared to Soxhlet or sonication
• Automated in-cell cleanup eliminating lengthy post-extraction procedures
• Enhanced throughput and reproducibility for environmental laboratories

These advantages support routine QA/QC of environmental samples with lower operational costs.

Future Trends and Opportunities

Further developments may include exploring alternative green solvents, miniaturized ASE systems for on-site monitoring, integration with high-resolution mass spectrometry, and extending the method to additional classes of persistent organic pollutants. Advances in sample preparation automation and selective sorbents can improve specificity and reduce analysis of complex matrices.

Conclusion

The presented ASE method successfully combines extraction and cleanup for PAHs and PCBs, striking a balance between efficiency and extract purity. Method 2 is particularly effective at minimizing coextractables while maintaining acceptable recoveries, simplifying workflow for environmental analysis.

Reference

Murphy B, Lingam S, Richter B, Carlson R. Simultaneous Extraction of PAHs and PCBs from Environmental Samples Using Accelerated Solvent Extraction. Thermo Fisher Scientific Application Note 1025; 2012.