Hydrocarbons, C1 – C6 - Separation of light hydrocarbons on a slightly polar porous polymer

Importance of the topic

Efficient separation of light hydrocarbons (C1–C6) is critical in petrochemical quality control, environmental monitoring, and fuel analysis. Fast, reliable gas chromatographic methods support process optimization, regulatory compliance, and research into hydrocarbon behavior under various conditions.

Objectives and study overview

This application note demonstrates the performance of an Agilent PoraPLOT S column in resolving 21 light hydrocarbons within a 14-minute run time. Key aims include evaluating separation efficiency, resolution of structural and positional isomers, and overall method robustness for routine analysis.

Methodology

A capillary gas chromatography method was developed using a wide-bore approach. Sample injections of 6 μL (0.1 % in nitrogen) were performed under isothermal conditions to maintain simplicity and reproducibility. Separation parameters were optimized to achieve baseline resolution for all target analytes within a short analysis window.

Instrumentation

• Gas chromatograph configured for wide-bore columns
• Agilent PoraPLOT S fused-silica PLOT column (0.53 mm × 25 m, df = 20 μm; Part no. CP7574)
• Carrier gas: Hydrogen at 40 cm/s linear velocity
• Injector: Direct injection at 100 °C
• Detector: Flame ionization detector (FID) at 150 °C

Main results and discussion

The developed method achieved clear separation of 21 hydrocarbons ranging from methane to neopentane in under 14 minutes. Key observations include:

• Baseline resolution of structural isomers such as isobutane vs. n-butane and cis- vs. trans-2-butene
• Sharp, symmetrical peaks for all components, indicating low interaction with the stationary phase
• Reproducible retention times across replicate injections, confirming method stability

These results highlight the PoraPLOT S column’s slightly polar porous polymer matrix, which balances adsorption and desorption kinetics to separate small hydrocarbons effectively.

Benefits and practical applications

• Rapid throughput enables high sample capacity in QA/QC labs
• Comprehensive isomer discrimination supports detailed hydrocarbon profiling
• Simplicity of isothermal operation reduces method complexity and maintenance
• Minimal thermal degradation ensures accurate quantitation of sensitive unsaturated species

Future trends and potential applications

Emerging developments may further enhance light hydrocarbon analysis:

• Integration with mass spectrometry for unambiguous compound identification and trace-level detection
• Miniaturized, portable GC systems for on-site process monitoring
• Automated sampling and data processing for real-time control in refineries and petrochemical plants
• Advanced polymeric stationary phases tailored for specific hydrocarbon subclasses

Conclusion

The Agilent PoraPLOT S column offers a robust, fast, and high-resolution solution for the separation of C1–C6 hydrocarbons. Its ability to resolve a broad range of light hydrocarbons in a single isothermal run makes it an attractive option for routine analyses in industrial and research laboratories.

References

Agilent Technologies, Inc. Application Note A01455, October 2011.