Alcohols and alkanes - Volatile alcohols and hydrocarbons in hexane

Significance of the topic

The determination of trace volatile alcohols and hydrocarbons in common solvent matrices is essential for ensuring sample purity, safeguarding analytical results, and complying with regulatory requirements in chemical, pharmaceutical, and petrochemical industries.

Objectives and Overview

This study demonstrates a gas chromatographic method for the simultaneous separation and detection of low-boiling alcohols and light hydrocarbons in a hexane solvent. By employing a nonpolar, thick-film fused silica column, the goal is to achieve sharp peak shapes and baseline resolution of early-eluting compounds prior to n-pentane.

Methodology and Instrumentation

The analysis uses capillary gas chromatography coupled with flame ionization detection (GC-FID). Key operational parameters include:

• Column: Agilent CP-Sil 5 CB, 0.32 mm ID × 50 m, df = 1.2 μm
• Oven temperature: isothermal at 45 °C
• Carrier gas: helium at 100 kPa (10 bar)
• Injection: split mode, 0.5 μL sample, split flow 30 mL/min, injector temperature 250 °C
• Detection: FID at 260 °C
• Sample composition: 0.1 % target analytes in hexane

Main Results and Discussion

The CP-Sil 5 CB column provided clear separation of methanol, ethanol, acetone, and 2-propanol ahead of the C5–C6 hydrocarbon fraction. Peak shapes were symmetrical and reproducible. The baseline resolution between n-pentane and early alcohols confirms the column’s suitability for simultaneous volatile alcohol and hydrocarbon profiling.

Benefits and Practical Applications

This rapid, isothermal GC-FID method enables quality control laboratories to screen solvent batches for trace contaminants and verify solvent purity before use in critical processes. Minimal sample preparation and standard instrumentation make it highly accessible.

Future Trends and Potential Applications

Emerging techniques such as multidimensional GC and tandem MS detection could further enhance selectivity and lower detection limits. Fast GC columns and automated headspace sampling may improve throughput in high-volume environments.

Conclusion

A single-run isothermal GC-FID approach on a CP-Sil 5 CB column effectively separates and quantifies volatile alcohols and hydrocarbons in hexane, supporting robust solvent quality assessments.

References

No external references were listed in the original document.