HPLC Detector Options for the Determination of Polynuclear Aromatic Hydrocarbons

Importance of the Topic

Polynuclear aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants generated by natural and industrial combustion processes. Several PAHs exhibit carcinogenic and mutagenic properties, leading to strict regulatory limits in water. Reliable detection and quantification of PAHs are therefore essential for environmental monitoring, public health protection, and compliance with EPA and European Community guidelines.

Objectives and Study Overview

This study evaluates two HPLC detector options for the analysis of 16 priority PAHs in water: UV absorbance at 254 nm and fluorescence detection with wavelength programming. The goal is to determine sensitivity, selectivity, and suitability for routine analysis according to EPA Method 610 and EC drinking water requirements.

Methodology

The separation of PAHs was achieved using reversed-phase gradient HPLC on two columns: a Vydac C18 (250 mm × 4.6 mm, 5 µm) and a Shandon Hypersil Green PAH column (100 mm × 4.6 mm, 5 µm). A binary gradient of acetonitrile and water at flow rates of 1.5–2.0 mL/min was employed. Samples were spiked with NIST Standard 1647 PAH mix and injected in 20 µL volumes. Detection methods compared:

• UV absorbance at 254 nm, with and without wavelength programming.
• Dual-monochromator fluorescence detector with programmed excitation and emission wavelengths.

Instrumentation

• Varian Star 9050 UV/Vis absorbance detector, wavelength programming capability.
• Varian 9070 dual-monochromator fluorescence detector, bandwidth 8 nm, excitation/emission programming.
• Vydac 201TP54 reversed-phase C18 column, 250 mm × 4.6 mm, 5 µm.
• Shandon Hypersil Green PAH column, 100 mm × 4.6 mm, 5 µm.

Main Results and Discussion

UV detection at 254 nm provided detection limits in the 0.004–0.31 µg/L range for the 16 PAHs, meeting EPA 610 requirements. Adding wavelength programming to the UV detector enhanced sensitivity by up to 35-fold for some compounds and improved selectivity by discriminating against coeluting matrix peaks. Fluorescence detection yielded substantially lower detection limits (down to 0.00012 µg/L for certain PAHs) and simplified chromatograms with reduced matrix interference. Sequential operation of UV followed by fluorescence detectors offered the highest combined sensitivity and selectivity, enabling reliable quantification at sub-µg/L levels required by EC and EPA standards.

Benefits and Practical Applications

• UV detection at 254 nm is straightforward, robust, and adequate for routine water analysis of PAHs under regulatory limits.
• Fluorescence detection with wavelength programming greatly enhances sensitivity and selectivity, facilitating analysis of complex matrices like soil or wastewater.
• Series configuration of UV and fluorescence detectors maximizes detection capabilities and ensures regulatory compliance.

Future Trends and Applications

Advances in detector technology, such as multi-wavelength programming and miniaturized fluorescence modules, will further improve on-site screening and real-time monitoring. Integration with mass spectrometry and the development of novel stationary phases tailored for PAHs could yield even lower detection limits and faster separations. Automated wavelength optimization algorithms promise to reduce method development time and enhance throughput in environmental laboratories.

Conclusion

Both UV absorbance at 254 nm and wavelength-programmed fluorescence detectors are effective for HPLC analysis of priority PAHs in water. UV detection offers simplicity and compliance with established methods, while fluorescence detection achieves superior sensitivity and cleaner chromatograms. A dual-detector approach delivers optimal performance for diverse sample types and stringent regulatory requirements.

References

1. Furata, N.; Otsuki, A. Analytical Chemistry 1983, 55, 2407–2413.