Select Polycyclic Aromatic Hydrocarbons (PAHs) on Rxi®-PAH (30 m x 0.25 mm ID x 0.10 μm df )

Importance of the topic

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental contaminants with known carcinogenic and mutagenic properties. Reliable detection and quantification of PAHs at trace levels are essential for environmental monitoring, food safety, and regulatory compliance. A robust analytical method enables laboratories to achieve high sensitivity, selectivity, and reproducibility when profiling complex PAH mixtures.

Goals and study overview

This application note evaluates a GC–MS method for the selective analysis of 41 priority PAHs using a Restek Rxi®-PAH capillary column. The study aims to demonstrate baseline separation of critical isobaric pairs, establish retention time windows, and optimize selected-ion monitoring (SIM) parameters in accordance with EPA Method 525.2.

Methodology and used instrumentation

The procedure employs the following setup:

• Column: Rxi-PAH, 30 m × 0.25 mm ID × 0.10 µm film thickness
• Carrier gas: Helium, constant flow at 2 mL/min
• Injection: Split mode (10:1), 0.5 µL volume, inlet temperature 275 °C, 2 mm deactivated wool liner
• Oven program: 110 °C (0.57 min), ramp to 175 °C at 65 °C/min, to 210 °C at 45 °C/min, to 295 °C at 5.3 °C/min, to 350 °C at 35 °C/min (hold 5 min)
• Detector: Quadrupole MS (Agilent 7890B GC & 5977A MSD) with transfer line at 330 °C
• Ionization: Electron impact (EI), source at 350 °C, quad at 200 °C, extractor lens 9 mm ID
• Acquisition: SIM mode using 18 time-segmented groups targeting diagnostic m/z for each PAH

Main results and discussion

The method achieves clear resolution of 41 PAHs within a 22-minute run time. Two critical isobar groups—cyclopenta[c,d]pyrene vs. triphenylene vs. chrysene, and benzo[b,k,j]fluoranthenes—are fully separated. Detection limits range from 0.010 to 1.0 ng on-column. Retention times correlate closely with molecular weight and ring structure. SIM transitions and dwell times are optimized to maximize sensitivity for low-abundance analytes while maintaining quantitative accuracy.

Benefits and practical applications

• High throughput: complete PAH profile in under 25 minutes
• Excellent selectivity: baseline separation of structural isomers
• Trace sensitivity: sub-nanogram detection limits
• Robust quantitation: internal standards and isotope-labeled surrogates compensate for matrix effects
• Versatility: applicable to water, soil, ambient air, and food matrices

Future trends and potential applications

Advancements in column technology and MS detectors will further reduce analysis time and improve sensitivity. Coupling with high-resolution MS or tandem MS may enhance identification of emerging PAH derivatives. Miniaturized GC systems and automated sample preparation workflows will expand on-site monitoring in environmental and industrial settings.

Conclusion

This GC–MS SIM method on the Rxi®-PAH column provides a reliable solution for comprehensive PAH analysis, delivering rapid separation, robust quantitation, and the ability to resolve challenging isobaric compounds. It meets regulatory requirements and supports a wide range of analytical applications.

Reference

No external literature references provided in the source document.