Identification of Polynuclear Aromatic Hydrocarbons in a Complex Matrix with Diode Array Detection

Significance of the Topic

The accurate identification and quantification of polynuclear aromatic hydrocarbons (PAHs) in environmental and industrial samples is essential for regulatory compliance, pollution monitoring and risk assessment. Traditional HPLC methods with single‐wavelength UV or fluorescence detection provide limited qualitative information, often requiring complementary techniques such as GC/MS. Incorporating diode array detectors enhances selectivity and confidence in compound identification by combining spectral and retention‐time data in a single run.

Objectives and Study Overview

This study evaluates the performance of a diode array detector (DAD) coupled with three different HPLC columns for rapid, reliable analysis of 16 priority PAHs in complex matrices. The primary aim is to determine whether DAD sensitivity meets EPA Method 610 requirements and to demonstrate how spectral library searching can confirm PAH identities without additional instrumentation.

Methodology and Instrumentation

A comparison was made among a Varian MicroPak SP-C18-5 column and two specialty PAH phases (Shandon Hypersil Green PAH and Vydac 201TP5415) under recommended gradient conditions. Standard mixtures of all 16 PAHs were run to build individual spectral libraries. Peak detection settings were optimized via PolyView software, using characteristic UV absorbance ranges (220–339 nm) and retention‐time windows to improve integration and identification accuracy. A coal tar extract containing 11 PAHs was analyzed to test performance in a real, complex sample matrix.

Instrumentation Used

• Polychrom diode array detector set at 254 nm with multi-wavelength peak sensing
• Varian MicroPak SP-C18-5 column (150 mm×4.0 mm, 4.5 μm, 80 Å)
• Shandon Hypersil Green PAH column (100 mm×4.6 mm, 5 μm, 120 Å)
• Vydac 201TP5415 column (150 mm×4.6 mm, 5 μm, 300 Å)

Main Results and Discussion

The DAD achieved detection limits comparable to single‐wavelength UV and met nearly all EPA 610 requirements, with limits for most PAHs below regulatory thresholds. Specialty PAH columns provided superior resolution for critical isomer pairs (e.g., acenaphthalene/fluorene, benzo(a)anthracene/chrysene) compared to the C18 phase. Library search results on the coal tar extract showed high similarity scores (>0.993) and low dissimilarity values (<0.12), confirming the accurate identification of PAHs even amidst numerous matrix interferences.

Benefits and Practical Applications

Combining specialty PAH columns with diode array detection streamlines PAH analysis by integrating confirmation and quantitation in one HPLC run. This approach reduces reliance on secondary techniques, shortens analysis time and enhances laboratory throughput for environmental monitoring, wastewater testing and industrial quality control.

Future Trends and Opportunities

Advances in spectral library automation and machine learning algorithms will further improve peak deconvolution and identification in complex matrices. Expanding diode array detector capabilities and column chemistries will enable routine analysis of emerging contaminants and broaden the scope of multi‐analyte environmental screening.

Conclusion

The study demonstrates that a diode array detector paired with optimized PAH columns meets stringent detection requirements and provides reliable compound confirmation in a single HPLC workflow. This methodology offers an efficient, cost‐effective alternative to multi‐step analytical protocols for environmental and industrial PAH analysis.

References

• USEPA Method 610 for Wastewater PAH Analysis
• LC Application Note #7: Fluorescence Detector Performance
• NIST Standard Reference Material 1547 Coal Tar Extract