16 Priority PAHs and Methylnaphthalenes on Rxi-5Sil MS using the GC Accelerator Kit in a 120 V Oven

Importance of the topic

Polycyclic aromatic hydrocarbons (PAHs) and methylnaphthalenes are widespread environmental contaminants with recognized carcinogenic and mutagenic effects. Accurate quantification is crucial for environmental monitoring, food safety assessment, and compliance with regulatory standards. Gas chromatography–mass spectrometry (GC–MS) offers the sensitivity and selectivity required to analyze these compounds at trace levels.

Objectives and Study Overview

This application note presents a rapid GC–MS method for the simultaneous separation and quantification of 16 EPA priority PAHs plus two methylnaphthalene isomers. The method leverages an Rxi-5Sil MS capillary column together with a GC Accelerator Kit in a 120 V oven. Selected ion monitoring (SIM) is used to enhance detection limits and selectivity within a streamlined temperature program.

Used Instrumentation

The analytical system comprised an Agilent 7890B GC coupled to a 5977A MSD. Key parameters included:

• Column: Rxi-5Sil MS, 20 m × 0.15 mm ID, 0.15 µm film thickness
• Oven: 120 V oven fitted with GC Accelerator Kit
• Injection: 1 µL split (20:1) using a Topaz 4 mm single taper liner with wool, injector at 275 °C
• Carrier gas: Helium at 1.0 mL/min (constant flow)
• Oven temperature program: 60 °C (0.7 min), ramp to 285 °C at 39.8 °C/min, to 305 °C at 4.3 °C/min, to 320 °C at 28.5 °C/min (3.5 min hold)
• MS conditions: Transfer line 280 °C, ion source 330 °C, quadrupole 180 °C, EI mode with DFTPP tune, SIM acquisition across ten time windows targeting characteristic m/z values

Main Results and Discussion

The method achieved baseline separation of all target compounds within a 15 min retention window. The valley between benzo[ghi]perylene peaks measured 71.6%, demonstrating excellent resolution. The SIM approach provided a detection limit of 0.05 ng on-column (1 µg/mL injection), with strong linearity and reproducible response factors for all analytes.

Benefits and Practical Applications

This protocol offers multiple advantages for routine laboratories:

• High throughput: total runtime under 30 min including temperature transitions
• Enhanced sensitivity and selectivity via targeted SIM acquisition
• Robust, reproducible separation on a nonpolar stationary phase optimized for PAHs
• Compatibility with EPA Method 8310 workflows, including surrogate and internal standard strategies

Future Trends and Potential Applications

Emerging developments may include ultra-fast GC techniques, two-dimensional GC–MS to resolve complex mixtures, and alternative ionization methods such as atmospheric pressure chemical ionization (APCI) to expand analyte scope. Integration of automated sample preparation and advanced data analytics will further increase throughput and data reliability.

Conclusion

The described GC–MS method using an Rxi-5Sil MS column and GC Accelerator Kit in a 120 V oven provides rapid, sensitive, and robust analysis of priority PAHs and methylnaphthalenes. Its adherence to regulatory guidelines and high-throughput capability make it well suited for environmental, food safety, and quality control laboratories.

References

• EPA Method 8310: Polycyclic Aromatic Hydrocarbons by GC–MS
• Restek Corporation Application Note: Fast SIM Analysis of PAHs with GC Accelerator Kit