Hydrocarbon Class Analysis of Conventional and Synthetic Aviation Turbine Fuels by ASTM D8396

Significance of the Topic

Gas chromatography coupled with comprehensive two-dimensional analysis (GCxGC-FID) is critical for detailed hydrocarbon profiling in aviation fuels, enabling detection of minor components obscured in conventional one-dimensional separations. Standard method ASTM D8396 provides a consensus-based protocol for class-type quantification without cryogenic modulation, enhancing accessibility and reliability in quality control and research laboratories.

Objectives and Study Overview

The study aims to evaluate the performance of the Agilent Reversed Flow Modulator (RFM) paired with the Agilent 8890 GC under ASTM D8396 conditions for both conventional jet fuels and synthetic aviation turbine fuels (SATF). Precision, retention time repeatability, and robustness were assessed using hydrogen and helium carriers across gravimetric and reference standards, SATF (FT-SPK and HEFA), kerosene materials, and a diesel-FAME blend.

Instrumentation Used

• Agilent 8890 Gas Chromatograph with 7693A autosampler
• Agilent Reversed Flow Modulator (cryogen-free CFT design)
• Columns: DB-17 (20 m×0.18 mm×0.18 µm), DB-1HT (5 m×0.32 mm×0.10 µm), deactivated fused silica restrictor lines
• Dual Flame Ionization Detectors
• Carrier gases: Hydrogen and Helium
• GC Image GCxGC Edition v2024r1 for data processing and template transformations

Methodology

Flow-modulated GCxGC was operated under a reversed column configuration with a 3.5 s modulation period for hydrogen and 6 s for helium. The oven program ramped from 40 °C to 230 °C at 3 °C/min, with injection volumes of 0.1 µL in split mode (400:1). Data were acquired at 200 Hz. Molecular class boundaries were defined by template‐based identification in GC Image, with affine transformations applied to reconcile retention shifts between carrier gases.

Main Results and Discussion

• Retention time repeatability showed near‐zero variance in both dimensions using Agilent’s sixth‐generation EPC control.
• Quantitative precision was below 1.0 %RSD for 39 of 42 compounds with hydrogen and all 42 compounds with helium.
• Hydrogen provided sharper peaks at high linear velocities, while helium required longer modulation periods and exhibited slight resolution loss in the paraffin region.
• GC Image’s interactive match and transform tool enabled rapid template realignment in under one minute, facilitating long‐term method robustness.
• Group‐type quantification of jet fuel, FT‐SPK, HEFA, kerosene, and diesel‐FAME mixtures yielded detailed class distributions revealing paraffin, isoparaffin, naphthene, and aromatic profiles.

Advantages and Practical Applications

• Cryogen-free, compact RFM provides the benchtop footprint of a conventional GC without specialized utilities.
• High resolution and reproducibility support QA/QC workflows for fuels, synthetic kerosenes, and biofuel blends.
• Template‐based data processing streamlines analysis of complex chromatograms containing over 1,000 peaks.
• Compatibility with both hydrogen and helium carriers allows laboratories to adapt to gas availability and safety requirements.

Future Trends and Applications

• Extension of GCxGC‐FID methods to heavier diesel and polyaromatic species by increasing oven temperatures to 300 °C.
• Integration of automated chemometric and machine‐learning workflows for rapid classification and anomaly detection in fuel analysis.
• Development of standardized multidimensional protocols for emerging sustainable aviation fuel (SAF) pathways.
• Broader adoption of cryogen‐free modulation systems in industrial laboratories for real‐time process monitoring.

Conclusions

The Agilent RFM combined with the 8890 GC delivers a robust, cryogen‐free solution for ASTM D8396 hydrocarbon class analysis, achieving exceptional retention repeatability and quantitative precision. Template‐based data processing in GC Image ensures reproducibility and ease of method maintenance across instrument platforms, supporting comprehensive fuel characterization in conventional and synthetic aviation applications.

References

1. Liu Z.; Phillips J. B. Comprehensive Two‐Dimensional Gas Chromatography using an On‐Column Thermal Modulator Interface. J. Chromatogr. Sci. 1991, 29(6), 227–231.
2. Hydrogen Safety. Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy, 2024.