Alcohols, alkanes - Separation of C11-C13 alkanes and C1- C4 alcohols

Importance of the topic

Gas chromatographic separation of mid-range alkanes and light alcohols is crucial for applications in energy fuels analysis, environmental monitoring, and quality control. Efficient, rapid, and selective methods enable accurate compositional profiling of complex mixtures in industrial and research settings.

Objectives and Study Overview

This application note presents the development of a capillary gas chromatography method to separate seven C11–C13 alkanes and four C1–C4 alcohols within a single 15-minute run. The study aims to demonstrate the selectivity and speed achievable using an Agilent TCEP porous layer open tubular column with flame ionization detection.

Methodology and Instrumentation

The separation was performed on an Agilent TCEP PLOT column (0.22 mm i.d., 50 m length, 0.4 µm film) under isothermal conditions at 90 °C. Nitrogen was used as the carrier gas at 0.9 bar (12.2 cm/s linear velocity). Injection was conducted in split mode (60 mL/min) with a 0.1 µL n-hexane solution. The flame ionization detector was set at 150 °C with high sensitivity (8 × 10⁻¹² Afs).

Used Instrumentation

• Agilent gas chromatograph with split injector
• Agilent TCEP PLOT capillary column (CP7525, 0.22 mm × 50 m, 0.4 µm)
• Flame ionization detector (FID) set at 150 °C

Main Results and Discussion

The optimized method achieved baseline separation of seven alkanes (n-undecane, n-dodecane, n-tridecane) and four alcohols (methanol, tert-butanol, isopropanol, n-butanol) within 15 minutes. The well-resolved peaks allowed straightforward identification and quantitation. Operating under isothermal conditions simplified method implementation while maintaining high resolution for both polar and nonpolar compounds.

Benefits and Practical Applications

• Rapid throughput suitable for routine quality control
• Simultaneous analysis of volatile and midchain analytes
• Isothermal operation reduces thermal stress and maintenance
• Suitable for fuel composition, petrochemical process, and environmental sample analysis

Future Trends and Opportunities

Future developments may include coupling to mass spectrometry for enhanced compound confirmation, employing hydrogen carrier gas for faster separations, and applying temperature programming or miniaturized columns to further reduce analysis time. Integration into online or automated systems will broaden industrial and environmental monitoring applications.

Conclusion

The presented GC-FID approach using an Agilent TCEP PLOT column delivers a fast, reliable, and robust solution for separating C11–C13 alkanes and C1–C4 alcohols. Its straightforward isothermal protocol and comprehensive coverage of analyte polarity make it a valuable tool for diverse analytical laboratories.