Analyses of Polychlorinated Biphenyl (PCB) Mixtures and Individual Congeners by GC

Importance of the Topic

The persistent environmental presence of polychlorinated biphenyls (PCBs) and their high toxicity have prompted strict regulatory guidelines by the US EPA. Effective monitoring of PCBs in water, soil, sediments, oils and biological tissues is essential for environmental protection and human health. Gas chromatographic methods combined with selective detectors remain the gold standard for qualitative and quantitative PCB analysis.

Objectives and Study Overview

This bulletin reviews chromatographic column packings, operating conditions, and sample preparation techniques for identifying and quantifying Aroclor PCB mixtures and individual congeners. It compares packed and capillary GC separations, highlights stationary phase selectivity, and presents solid phase microextraction (SPME) for rapid, solvent-free sample enrichment.

Methodology

Sample preparation varies by matrix:

• Transformer or waste oils: dilution in solvent.
• Aqueous, sedimentary or biological samples: solvent extraction, concentration, clean-up.
• Modern approaches: solid phase extraction and microextraction (SPME) for headspace or direct immersion.

Chromatographic separation involves temperature programming and carrier gas control to resolve complex PCB patterns or individual congeners.

Instrumentation

• Packed columns: 1.5% SP-2250/1.95% SP-2401 on 100/120 SUPELCOPORT and 3% SP-2100 on 100/120 SUPELCOPORT (EPA Method 608 compliant).
• Capillary columns: SPB-Octyl (shape-selective for coplanar congeners), SPB-608, SPB-5, PTE-5, and wide-bore capillaries (0.53 mm or 0.75 mm ID) for high-resolution separations.
• Detectors: electron capture detector (ECD) for high sensitivity; mass spectrometer (MSD or ion trap) for selectivity and extracted ion monitoring.
• Microextraction device: polydimethylsiloxane-coated fiber for SPME headspace or immersion sampling.

Main Results and Discussion

• Packed-column GC reliably identifies and quantifies intact Aroclor mixtures by characteristic elution patterns; choice of SP-2250/SP-2401 yields better peak spread for pattern recognition, while SP-2100 offers faster runs.
• Capillary GC resolves degraded or mixed PCB samples and separates individual congeners; SPB-Octyl phase exhibits unique boiling-point correlated selectivity that separates coplanar, toxic homologs.
• Mass spectrometric detection with extracted ion chromatograms overcomes homolog overlap and enables accurate quantification of coeluting congeners.
• SPME combined with capillary GC achieves ppt-level detection of PCBs in sediments without using solvents, demonstrating clean profiles matching Aroclor standards.

Benefits and Practical Applications

• Compliance with EPA monitoring methods for wastewater, oils, sediments and tissues.
• Flexible column selection based on sample complexity and throughput requirements.
• Enhanced congener-specific analysis of toxic dioxin-like PCBs using shape-selective stationary phases.
• Streamlined, solvent-free SPME sample preparation reduces costs and environmental impact.

Future Trends and Applications

Advances will likely include broader adoption of ultra-high-selectivity stationary phases for targeted congener analysis, integration of SPME with portable GC systems for on-site screening, utilization of tandem mass spectrometry for lower detection limits, and automated data processing with pattern-recognition software to accelerate routine environmental and industrial PCB monitoring.

Conclusion

This overview demonstrates comprehensive strategies for PCB analysis by GC, from routine identification of Aroclor mixtures on packed columns to high-resolution congener separations on capillaries and innovative SPME sample prep. Careful selection of column chemistry, detector type and extraction technique ensures reliable, sensitive and selective monitoring of PCBs in diverse matrices in accordance with regulatory requirements.

References

• US EPA Methods 600/4-81-045, 600/4-82-057, SW-846 Method 608
• Ballschmiter K. et al. J HRC 15:260-270 (1992)
• McFarland VA, Clarke JU. Environ Health Perspect 81:225-239 (1989)
• Ahlborg UG et al. Chemosphere 28:1049-1067 (1994)
• Safe S. Crit Rev Toxicol 21:51-88 (1990)
• Brown JF Jr. Environ Sci Technol 28:2295-2305 (1994)