Polyaromatic hydrocarbons - Analysis of EPA 625 PAH

Significance of the Topic

Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants generated by incomplete combustion of organic material. Many PAHs are recognized as mutagenic and carcinogenic, making their accurate determination in environmental samples essential to assess human exposure and ecological risks.

Objectives and Overview

This application note presents a gas chromatographic method for rapid separation and quantification of the 16 PAHs defined in EPA Method 625. The goal is to achieve baseline resolution within 30 minutes using an advanced capillary column and flame ionization detection.

Methodology and Used Instrumentation

The analysis employs gas chromatography with flame ionization detection (GC-FID). Key conditions include:

• Column: Agilent FactorFour VF-200ms, 0.25 mm × 30 m, 0.25 µm film thickness
• Temperature program: initial 45 °C, ramp at 10 °C/min to 325 °C
• Carrier gas: helium at ~1.0 mL/min, constant pressure of 60 kPa
• Injector: split mode (1:100), injection volume 1 µL
• Detector: flame ionization detector (FID)
• Solvent: methylene chloride, 2000 µg/mL standard concentration

Main Results and Discussion

The VF-200ms column achieved complete separation of all 16 EPA PAHs in under 30 minutes. Early eluting compounds such as naphthalene and acenaphthylene were resolved within minutes, while higher-molecular-weight congeners including indeno[1,2,3-cd]pyrene and benzo[g,h,i]perylene were clearly separated near the end of the run. Peak shapes were sharp and symmetrical, facilitating accurate integration and quantification.

Reproducibility tests showed retention time variations below 0.1 %, and calibration curves exhibited linearity over the concentration range with correlation coefficients exceeding 0.999.

Benefits and Practical Applications

This method delivers high throughput and robust performance for environmental laboratories conducting routine monitoring of water, soil, and air matrices. The fast separation reduces cycle times and solvent consumption. GC-FID provides reliable quantitation with lower operational cost compared to mass spectrometric detection while maintaining sensitivity suitable for regulatory compliance.

Future Trends and Potential Applications

Advances in column technology may further shorten analysis times and improve resolution. Coupling with mass spectrometry (GC-MS) can enhance specificity for complex matrices. Integration of automated sample preparation and on-line extraction will streamline workflows. Emerging portable and field-deployable GC instruments promise real-time PAH monitoring for rapid decision making in environmental emergencies.

Conclusion

The described GC-FID method on an Agilent VF-200ms column offers a rapid, reliable, and cost-effective solution for quantifying the 16 EPA PAHs. Its high resolution, reproducibility, and throughput make it well suited for routine environmental analysis and regulatory compliance.

References

• Agilent Technologies, Inc. Application Note A02202, "Analysis of EPA 625 PAH", First published prior to 11 May 2010; revised 31 October 2011.