Resolution of Indeno[123-cd]pyrene from Dibenz Anthracene Isomers on Rxi®-PAH (60 m x 0.25 mm x 0.10 μm)

Importance of the topic

The selective separation of polycyclic aromatic hydrocarbon (PAH) isomers such as dibenzo[a,c]anthracene and indeno[1,2,3-cd]pyrene is critical for environmental monitoring, food safety, and industrial quality control. Accurate resolution of these compounds enables reliable quantification of toxic species in complex samples and supports regulatory compliance.

Objectives and Study Overview

The primary goal was to achieve complete chromatographic separation of closely eluting PAH isomers using a high-efficiency capillary column. This study evaluated retention behavior, peak resolution, and quantitation performance for eight target analytes in a simulated standard mixture.

Methodology

A split injection of a mixed PAH standard in toluene was performed on a gas chromatograph–mass spectrometer operating in selected ion monitoring (SIM) mode. The concentration range for analytes spanned from 0.71 to 10 µg/mL. The oven temperature ramp was optimized to separate isomers with minimal coelution.

Instrumental Setup

• Column: Rxi–PAH, 60 m × 0.25 mm ID, 0.10 µm film thickness
• GC: Agilent 7890B with split ratio 10:1, injection at 275 °C
• MSD: Agilent 5977A quadrupole, electron ionization at 70 eV
• Carrier gas: Helium at 1.0 mL/min constant flow
• Temperature program: 110 °C (1.6 min) → 175 °C at 30 °C/min → 265 °C at 1.6 °C/min → 350 °C at 4 °C/min (15 min hold)
• SIM transitions: m/z values selected to distinguish each PAH isomer

Main Results and Discussion

Baseline resolution was achieved between dibenzo[a,c]anthracene (tR 75.18 min) and indeno[1,2,3-cd]pyrene (tR 75.31 min). All eight analytes displayed distinct peaks with reproducible retention times. Key observations included:

• High peak capacity enabled clear separation of structurally similar PAHs.
• SIM detection provided sensitive and selective quantitation at low µg/mL levels.
• The optimized temperature gradient minimized run time while maintaining resolution.

Benefits and Practical Applications

The method delivers robust performance for trace-level PAH analysis in environmental, food, and petrochemical samples. Benefits include:

• Reliable isomer discrimination to meet regulatory requirements.
• Reduced analysis time with high-resolution separations.
• Sensitivity enhancement via targeted SIM acquisition.

Future Trends and Opportunities

Emerging needs for faster screening and automated workflows may drive adoption of ultra-fast GC or multidimensional chromatography. Integration with high-resolution mass spectrometry and machine-learning algorithms could further enhance selectivity and data processing.

Conclusion

This work demonstrates a validated GC–MS approach for resolving challenging PAH isomer pairs using an Rxi–PAH column and SIM detection. The protocol offers reliable quantitation and can be adapted for routine monitoring in diverse analytical laboratories.