Alcohols, C1 – C4, aromatic hydrocarbons, C5 – C7 - Analysis of gasoline

Significance of the Topic

Precise quantification of C1–C4 alcohols and C5–C7 aromatic hydrocarbons in gasoline is essential for quality control, environmental compliance and engine performance optimization. These volatile organic compounds influence octane rating, emissions profile and storage stability, making reliable analytical methods indispensable in fuel analysis laboratories.

Objectives and Study Overview

This application note demonstrates a rapid gas chromatographic method for simultaneous separation and quantification of eleven target analytes in gasoline. The aim is to achieve baseline resolution of light alcohols and mid-range aromatics within a single 27-minute run using an optimized Agilent CP-TCEP column and flame ionization detection.

Methodology and Instrumentation

The method employs capillary gas chromatography with a 50 m × 0.25 mm CP-TCEP column (0.4 µm film thickness). A temperature program from 70 °C (10 min) to 120 °C at 5 °C/min, followed by an 8 min hold at 120 °C, ensures effective separation. Nitrogen at 90 kPa serves as carrier gas. Samples (0.5 µL) are introduced via split injection (50 mL/min), and detection is by flame ionization.

Main Results and Discussion

The optimized conditions resolve eleven peaks, including t-butanol, methanol, benzene, methyl ethyl ketone (internal standard), toluene, ethylbenzene, p-xylene, m-xylene, n-butanol, o-xylene and higher aromatics (Solvesso-100). Retention times are consistent, and peak shapes are sharp with minimal tailing. Nitrogen carrier gas provides improved selectivity for light alcohols. Reproducibility studies show relative standard deviations below 2% for retention times and peak areas.

Benefits and Practical Applications

• Comprehensive profiling of light alcohols and aromatics in a single run.
• Short analysis time increases sample throughput in QA/QC environments.
• High resolution and reproducibility support regulatory compliance (e.g., ASTM, EN standards).
• Simple method adapts to routine monitoring in fuel production and research laboratories.

Future Trends and Applications

Advances in fast GC and miniaturized columns could further reduce analysis time. Coupling with mass spectrometry may enhance specificity for trace-level impurities. Emerging detector technologies like vacuum ultraviolet (VUV) spectroscopy offer multi-component detection without chromatographic separation. Automated sample preparation and online monitoring systems can support real-time fuel quality control.

Conclusion

The presented GC-FID method on an Agilent CP-TCEP column provides a robust, high-throughput solution for quantifying key alcohol and aromatic constituents in gasoline. Its reliability and ease of implementation make it a valuable tool for fuel analysis and regulatory compliance.

Reference

Agilent Technologies, Inc. (2011) Application Note A00590: Analysis of C1–C4 Alcohols and C5–C7 Aromatic Hydrocarbons in Gasoline Using an Agilent CP-TCEP Column.