Determination of Aromatic Hydrocarbons in Jet Fuel by LC-RID According to ASTM D6379 / IP436 using a Single Column

Importance of the Topic

The accurate quantitation of mono- and di-aromatic hydrocarbons in aviation fuels is essential for assessing fuel quality, combustion performance and compliance with environmental regulations. Aromatic content influences octane pressure, soot formation and thermal stability, which are critical factors for safe and efficient aircraft operation.

Aims and Overview of the Study

This study presents an alternative HPLC method using refractive index detection (RID) and a single amino column to measure aromatic content in jet fuels according to ASTM D6379 and IP436. It examines method validation, linearity, precision and applicability to real-world samples, providing a robust alternative to fluorescence-based ASTM D1319.

Methodology

The method employs high-performance liquid chromatography with a Shimadzu Prominence system. A Shim-pack GIST NH2 column (4.6×250 mm, 3 µm) and guard were used for separation. Heptane served as the mobile phase at 1.0 mL/min. The column and RID temperatures were maintained at 35 °C. Sample injections of 1 µL were analyzed without valve switching. Calibration involved four standards of cyclohexane, o-xylene and 1-methylnaphthalene ranging from 0.05 to 15 mg/mL.

Used Instrumentation

• Shimadzu Prominence HPLC system
• LC-20AD pump and DGU-20A3R degasser
• SIL-20AC autosampler
• CTO-20A column oven with 6-port valve
• RID-20A refractive index detector

Main Results and Discussion

System resolution standard injections achieved clear separation: cyclohexane at 3.46 min, o-xylene at 4.86 min, and 1-methylnaphthalene at 6.08 min. Resolution between cyclohexane and o-xylene was 7.1, exceeding method requirements of 5.0 (ASTM) and 5.7 (IP). Calibration curves for o-xylene and 1-methylnaphthalene were highly linear (r²=0.9999). Precision testing yielded RSDs below 0.2% for retention times and peak areas. Analysis of a Jet A sample diluted 1:10 in heptane demonstrated effective separation of saturates, mono- and di-aromatics suitable for quantitation.

Benefits and Practical Applications

This method provides:

• A reliable alternative to ASTM D1319 without reliance on discontinued fluorescent dyes
• High linearity and precision for aromatic quantitation
• Streamlined analysis using a single column and minimal valve operations
• Compatibility with routine QA/QC workflows in aviation fuel testing laboratories

Future Trends and Potential Applications

Expanding this approach to other distillate fuels can enhance analytical versatility. Integration with automated back-flushing protocols could further reduce downtime and extend column life. Emerging detectors and column chemistries may allow simultaneous monitoring of higher polyaromatic fractions.

Conclusion

The Shimadzu Prominence HPLC method with RID detection and a single amino column offers a robust, compliant and efficient approach for determining aromatic hydrocarbon content in jet fuels. Its high resolution, linearity and precision make it a strong replacement for outdated fluorescence-based techniques.

References

• ASTM D1319-18. Standard Test Method for Hydrocarbon Types in Liquid Petroleum Products by Fluorescent Indicator Adsorption. ASTM International, 2018.
• ASTM D6379-11. Standard Test Method for Determination of Aromatic Hydrocarbon Types in Aviation Fuels and Petroleum Distillates — HPLC Method with RID. ASTM International, 2011.