Determination of Aromatic Hydrocarbons in Jet Fuel by LC-RID According to ASTM D6379 / IP436 using a Two-column Set

Importance of the topic

The accurate determination of mono- and di-aromatic hydrocarbons in jet fuels is critical for evaluating fuel quality, combustion performance and compliance with safety and environmental regulations. Aromatic content influences key properties such as density, energy content and emission profiles, making reliable analytical methods indispensable for aviation and industrial applications.

Objectives and overview of the study

This study demonstrates a high performance liquid chromatography method with refractive index detection for quantifying aromatic hydrocarbons in aviation fuels in accordance with ASTM D6379 and IP436. It aims to provide an alternative to the discontinued fluorescent dye based ASTM D1319 method by employing a two-column approach that also meets ASTM D6591 requirements, enabling versatile application on a single instrument.

Methodology and instrumentation

A Shimadzu Prominence HPLC system was employed, including LC-20AD pump, DGU-20A3R degasser, SIL-20AC autosampler, CTO-20A column oven with a 6-port 2-position valve and RID-20A refractive index detector. Software control used LabSolutions LC/GC. Separation was achieved on a two-column set: Shim-pack GIST NH2 4.6×250 mm 5 µm and Shim-pack GIS CN 4.6×150 mm 5 µm, with heptane as mobile phase at 1 mL/min. Operating conditions were injection volume 1 µL, column and detector temperature 35 °C. The valve remained in position for compatibility with additional methods without actuation. Calibration standards from an ASTM D6379 kit included defined concentrations of cyclohexane, o-xylene and 1-methylnaphthalene.

Main results and discussion

The system resolution standard achieved clear separation of key peaks: cyclohexane at 5.10 min, o-xylene at 6.56 min and 1-methylnaphthalene at 8.02 min, with a resolution of 8.9 between cyclohexane and o-xylene, exceeding method requirements. Calibration curves for aromatic analytes were linear with r2 of 0.9999. Precision testing on three replicate injections of Standard 2 yielded relative standard deviations below 0.5 % for retention times and below 0.3 % for peak areas. A real Jet A fuel sample diluted 1:10 in heptane produced a well-resolved chromatogram suitable for quantitation per ASTM D6379.

Benefits and practical applications

This HPLC-RID method offers a robust and reproducible approach for routine analysis of aviation and middle distillate fuels, replacing outdated fluorescence-based assays. The two-column set reduces analysis time and maintenance requirements. Compliance with multiple ASTM standards on a single configuration enhances laboratory throughput and operational efficiency.

Future trends and potential applications

Developments may include coupling with mass spectrometric detection for enhanced specificity, miniaturized column formats for faster throughput, and automated on-site monitoring systems for real-time fuel quality assessment. Adoption of greener solvents and advanced data analytics could further advance fuel hydrocarbon profiling.

Conclusion

The described HPLC-RID method meets ASTM D6379 and IP436 requirements for aromatic hydrocarbon determination in jet fuels. It delivers high resolution, linear response and precision, representing a reliable alternative to fluorescence-based methods and allowing multiple tests on a single instrument.

References

• ASTM D1319-18 Standard Test Method for Hydrocarbon Types in Liquid Petroleum Products by Fluorescent Indicator Adsorption
• ASTM D6591-18 Standard Test Method for Determination of Aromatic Hydrocarbon Types in Middle Distillates by HPLC with Refractive Index Detection
• ASTM D6379-11 Standard Test Method for Determination of Aromatic Hydrocarbon Types in Aviation Fuels and Petroleum Distillates by HPLC with Refractive Index Detection