Select PAHs on Rxi®-PAH (60 m x 0.25 mm x 0.10 μm)

Importance of the topic

Polycyclic aromatic hydrocarbons (PAHs) are priority environmental pollutants due to their persistence, toxicity, and potential carcinogenicity. Accurate measurement of PAH profiles in air, water, soil, and consumer products is essential for regulatory compliance, risk assessment, and process monitoring. Gas chromatography–mass spectrometry (GC–MS) in selected ion monitoring (SIM) mode offers high sensitivity and selectivity, while specialized stationary phases like the Rxi®-PAH column deliver improved resolution of isomeric species.

Study Objectives and Overview

This application note evaluates the performance of a 60 m × 0.25 mm × 0.10 µm Rxi-PAH capillary column coupled to an Agilent 7890B GC and 5977A MSD in SIM mode for the separation and quantification of 52 PAHs. Key goals included:

• Achieve baseline separation of structural isomers
• Establish retention times and quantification ions for each analyte
• Demonstrate linearity over 0.71–10 µg/mL concentration range

Methodology and Instrumentation

Samples consisted of mixtures of deuterated internal standards and native PAH calibration solutions in toluene. A 1 µL split injection (10:1) delivered analytes onto the column. The temperature program began at 110 °C (1.6 min), ramped to 175 °C at 30 °C/min, to 265 °C at 1.6 °C/min, and finally to 350 °C at 4 °C/min (15 min hold). Helium carrier flow was 1.0 mL/min. The MSD operated in electron ionization (EI) SIM mode, with compound-specific ions and 20 ms dwell times to maximize sensitivity.

Applied Instrumentation

• Column: Rxi®-PAH, 60 m × 0.25 mm ID, 0.10 µm film thickness
• GC: Agilent 7890B with Premium 4 mm Precision® liner w/wool
• MS: Agilent 5977A Quadrupole MS in SIM mode, transfer line at 320 °C, source 350 °C, quadrupole 200 °C
• Software: EZGC® for method optimization

Main Results and Discussion

The method resolved 52 PAHs with retention times spanning 6.17 to 84.88 min. Deuterated surrogates ensured accurate quantification. Critical separations included dibenzo[a,c]anthracene vs dibenzo[a,h]anthracene, indeno[1,2,3-cd]pyrene; triphenylene vs chrysene; and benzofluoranthene isomers. Response was linear across the calibration range, and the use of SIM improved signal-to-noise for low-level analytes.

Benefits and Practical Applications

This GC–MS SIM method provides:

• High resolution of isomeric PAHs for confident identification
• Enhanced sensitivity and low detection limits via SIM
• Robust quantification using deuterated internal standards
• Applicability to environmental monitoring, food safety, and industrial QA/QC

Future Trends and Potential Applications

Emerging prospects include coupling Rxi®-PAH separations with high-resolution MS for non-target screening, integrating automated sampling for high throughput, and exploring miniaturized or multidimensional GC approaches to further reduce analysis time while maintaining resolution. Advances in data analytics may enhance profiling of complex PAH mixtures in environmental and biological matrices.

Conclusion

The Rxi®-PAH column combined with GC–MS SIM delivers reliable, high-resolution separation and quantification of a broad suite of PAHs. The demonstrated method meets regulatory and research needs for trace-level PAH analysis across various matrices.

References

No external references were cited in the original application note.