GC Analyses of Polynuclear Aromatic Hydrocarbons

Importance of the Topic

The analysis of polynuclear aromatic hydrocarbons (PAHs) is critical due to their toxic and carcinogenic properties and their designation as priority pollutants by the US EPA. Accurate separation and quantification in environmental samples such as wastewater are essential for regulatory compliance, environmental monitoring, and public health protection.

Objectives and Study Overview

This application note evaluates gas chromatography techniques for the separation of the 16 EPA-defined priority PAHs. It compares packed column and capillary column approaches, details optimal conditions for each method, and reviews the limits and standards suitable for routine environmental analysis.

Methodology

Two main GC approaches were examined:

• Capillary GC using SPB-5 bonded phase fused silica columns to resolve all 16 PAHs with sharp, symmetrical peaks.
• Packed column GC employing a liquid crystal stationary phase (1.5% SP-301 on SUPELCOPORT) to separate critical isomeric pairs and mixed-phase columns for complex matrices like creosote.

Used Instrumentation

• Capillary columns: SPB-5, 30m×0.25mm ID×0.25µm film and wide bore variants (60m×0.75mm ID×1.0µm film); helium carrier gas; flame ionization detection (FID); split and splitless injection.
• Packed columns: Glass and stainless steel columns packed with 1.5% SP-301 or mixed SP-2100/BMBT phases; nitrogen carrier gas; FID detection.
• Oven temperature programs ranging from 100°C to over 300°C to ensure elution of high-boiling PAHs.

Main Results and Discussion

The SPB-5 capillary column provided baseline resolution for all 16 priority PAHs, including challenging isomeric pairs such as benzo(a)pyrene and benzo(e)pyrene. Packed columns with SP-301 resolved benzo(a)anthracene from chrysene but showed some coelution of higher molecular weight compounds. Mixed-phase packing on SUPELCOPORT supports enabled the analysis of phenanthrene, anthracene, and carbazole in creosote samples. The stability and high temperature tolerance of crosslinked stationary phases contributed to reliable, reproducible separations.

Benefits and Practical Applications

• Enhanced resolution of priority PAHs for trace-level environmental monitoring.
• Compatibility with EPA Method 610 workflows for wastewater analysis.
• Extended column lifetime at elevated temperatures.
• Flexibility to use both capillary and packed column formats in existing GC systems.

Future Trends and Potential Applications

Advancements may include integration with mass spectrometry for improved sensitivity, the development of novel stationary phases for faster separations, miniaturized GC devices for field analysis, and automated sample preparation to increase throughput in environmental laboratories.

Conclusion

Optimized GC methods using SPB-5 capillary and SP-301 packed columns provide robust, high-resolution analysis of the 16 EPA priority PAHs. These techniques support regulatory compliance and offer versatile solutions for routine environmental monitoring.

Reference

1. Federal Register, 44: 233 (Dec. 3, 1979).