Hydrocarbons, C4 – C12

Importance of the topic

Gas‐phase analysis of mid‐range hydrocarbons (C4–C12) is fundamental for fuel quality control, petrochemical process monitoring and environmental assessment. Accurate separation and identification of structural isomers among light hydrocarbons support regulatory compliance, process optimization and forensic investigations. The ability to resolve a large number of branched, cyclic and unsaturated species enhances our understanding of hydrocarbon streams and contributes to improved product specifications.

Objectives and study overview

This application note presents a comprehensive evaluation of an Agilent CP-Sil PONA CB capillary column for high‐resolution separation of more than 165 C4–C12 hydrocarbons in a single 130-minute run. The study aims to demonstrate retention behavior, peak capacity and isomer discrimination across a complex hydrocarbon mixture, offering a reliable protocol for routine analysis in energy and fuels laboratories.

Methodology and instrumentation

A gas chromatography system equipped with a 0.25 mm × 100 m CP-Sil PONA CB fused silica column (0.5 µm film thickness) was employed. Key operating conditions:

• Oven temperature program: 0 °C (15 min) → 50 °C at 1 °C/min → 130 °C at 2 °C/min → 180 °C at 4 °C/min (20 min hold)
• Carrier gas: Helium at 260 kPa (37 psi), linear velocity 22.1 cm/s
• Injection: Split mode at 200 °C, 200 mL/min split flow, 0.15 µL sample
• Detection: Flame ionization detector at 250 °C

Main results and discussion

The method achieved baseline separation for over 165 distinct C4–C12 hydrocarbons, including constitutional and stereoisomers. Early eluting C4–C6 species were well resolved, with clear discrimination of butane and butene isomers, while mid‐boiling C7–C9 fractions showed effective separation of cyclic and branched components. The longer chain C10–C12 paraffins and aromatics eluted later with maintained resolution. Several peaks received tentative identification, demonstrating the method’s sensitivity to minor isomers and trace components.

Benefits and practical applications

The described method offers laboratories a robust platform for:

• Quality control of gasoline and light distillates
• Characterization of petrochemical feedstocks
• Environmental and emissions testing
• Research on isomerization and cracking processes

The long column and optimized temperature program ensure high peak capacity and reproducibility, supporting both routine workflows and detailed structural studies.

Future trends and potential applications

Advances in column technology, such as narrower bore, thinner films and novel stationary phases, will reduce analysis time and boost resolution. Integration with comprehensive two‐dimensional GC (GC×GC) or coupling to mass spectrometry will enable deeper profiling of complex mixtures. Automated data processing and machine‐learning algorithms are poised to streamline isomer identification and quantitation in high‐throughput environments.

Conclusion

The Agilent CP-Sil PONA CB column method delivers exceptional separation of a broad range of C4–C12 hydrocarbons, combining high resolution with practical run times. Its application supports critical quality assurance, process control and research activities in energy and fuels analysis.

Reference

Agilent Technologies, Inc. Application Note A00602, Hydrocarbons C4–C12, Energy & Fuels, October 2011.