Resolution of Benzo Fluoranthene and Benzo Pyrene Isomers on Rxi®-PAH (60 m x 0.25 mm x 0.10 μm)

Significance of the Topic

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed environmental contaminants with known carcinogenic and mutagenic properties. Precise separation of PAH isomers such as benzo[b/k/j]fluoranthene and benzo[e/a]pyrene is critical for accurate quantification in environmental monitoring, food safety testing, and regulatory compliance. High-resolution gas chromatography coupled with mass spectrometry (GC-MS) offers the selectivity and sensitivity required for these analyses.

Objectives and Study Overview

This study aims to demonstrate the capability of the Rxi®-PAH GC column to achieve baseline separation of structurally similar PAH isomers. The work focuses on method development and optimization of GC-MS parameters to resolve benzo fluoranthene and benzo pyrene isomeric pairs within a single analytical run.

Methodology and Instrumentation

The method employs an Agilent 7890B gas chromatograph coupled to a 5977A mass selective detector operated in selected ion monitoring (SIM) mode. Key parameters include:

• Column: Rxi-PAH, 60 m × 0.25 mm ID, 0.10 µm film thickness
• Carrier gas: Helium at constant flow of 1.0 mL/min
• Injection: 1 µL split (10:1) at 275 °C using a wool-packed liner
• Oven program: 110 °C (1.6 min hold) → 175 °C at 30 °C/min → 265 °C at 1.6 °C/min → 350 °C at 4 °C/min (15 min hold)
• MS conditions: EI source at 350 °C, quadrupole at 200 °C, transfer line at 320 °C, SIM with m/z 252 quantifier for target compounds

Main Results and Discussion

The optimized method achieves excellent resolution of benzo[b], benzo[k], and benzo[j]fluoranthene, with retention times at 63.86 min, 64.13 min, and 64.29 min, respectively. Benzo[a]fluoranthene and benzo[e]pyrene elute at 65.10 min and 67.15 min, followed by benzo[a]pyrene at 67.63 min and perylene at 68.62 min. Calibration across 0.71 to 10 µg/mL demonstrated linear response and robust quantitation. The method also resolves dibenzo[a,c]anthracene, dibenzo[a,h]anthracene, indeno[1,2,3-cd]pyrene, triphenylene, and chrysene isomers.

Benefits and Practical Applications

Reliable isomer separation enables:

• Accurate environmental PAH profiling for risk assessment
• Quality control in food and beverage safety testing
• Regulatory compliance in air and water monitoring programs
• Standardized protocols for QA/QC laboratories

Future Trends and Potential Applications

Emerging directions include two-dimensional GC×GC for enhanced peak capacity, high-resolution accurate-mass (HRAM) MS for improved selectivity, and miniaturized GC systems for field analysis. Advances in green solvents and automated data processing will further streamline PAH analysis workflows.

Conclusion

The Rxi®-PAH column paired with optimized GC-MS SIM conditions delivers baseline separation of critical PAH isomers. This method supports accurate quantitation and robust performance for environmental and industrial applications.