Detection and Quantification of Fatty Acid Methyl Esters (FAMES) in Jet Fuel by GCxGC-TOFMS

Importance of the Topic

Jet fuel contamination by fatty acid methyl esters (FAMEs) from residual biodiesel poses significant risks to engine performance and safety. Even trace levels of FAMEs adhering to pipeline walls or containers can alter combustion properties and lead to operational failures. International specifications limit FAME content in jet fuel to below 5 mg/kg to ensure consistent fuel quality and prevent off-specification issues.

Objectives and Study Overview

This study evaluates a comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GCxGC-TOFMS) method for sensitive detection and quantification of six common FAMEs in JP-8 jet fuel. Key aims include:

• Establishing calibration curves over low (0–10 mg/kg) and broad (0–100 mg/kg) concentration ranges.
• Validating linearity, precision, and accuracy of FAME quantification.
• Demonstrating method robustness through spiked sample analysis.

Methodology and Instrumentation

Sample preparation involved spiking JP-8 with FAME standards (methyl hexadecanoate, methyl heptadecanoate-d33 internal standard, methyl heptadecanoate, methyl linoleate, methyl oleate, methyl linolenate, methyl stearate) in dodecane across designated concentration levels. Two calibration ranges were generated:

• 0–10 mg/kg by splitless injection.
• 0–100 mg/kg by 20:1 split injection.

The GCxGC-TOFMS setup comprised:

• Agilent 7890 GC with LECO Pegasus 4D TOFMS detector.
• First-dimension Rxi-5Sil MS (30 m × 0.25 mm × 0.25 µm) and second-dimension Stabilwax® (1.6 m × 0.25 mm × 0.25 µm) columns.
• Helium carrier gas (1.0 mL/min) and thermal modulation.
• Temperature program: 105 °C (2 min) → 190 °C @10 °C/min → 230 °C @2 °C/min (5 min).
• TOFMS acquisition: m/z 35–750 at 200 spectra/s, ion source 230 °C.

Main Results and Discussion

Method blanks confirmed negligible carryover. Calibration curves exhibited excellent linearity (R² > 0.99) across both ranges. A 10 mg/kg FAME spike in JP-8 yielded clear chromatographic separation and accurate quantification of each compound. Expanded calibration up to 100 mg/kg maintained linearity, demonstrating method flexibility. The comprehensive GCxGC separation minimized co-elution and enhanced spectral clarity for confident library matching and quant mass extraction.

Benefits and Practical Applications of the Method

This GCxGC-TOFMS approach offers:

• High sensitivity and selectivity for multiple FAME analytes in a single run.
• Robust quantification without relying on SIM modes.
• Rapid analysis (<36 min) suitable for routine quality control in fuel production and distribution.

Future Trends and Potential Applications

Advances in two-dimensional chromatography and high-resolution mass spectrometry will further improve resolution of complex fuel matrices. Coupling with automated data processing and AI-driven spectral libraries may enhance throughput and detection confidence. The methodology could extend to other fuel contaminants and biofuel blends, supporting stricter environmental and regulatory monitoring.

Conclusion

The presented GCxGC-TOFMS method delivers a fast, sensitive, and reliable platform for detecting and quantifying FAME contamination in jet fuel. Its strong linearity, comprehensive separation, and full-range spectral acquisition make it a valuable tool for ensuring compliance with stringent fuel specifications and safeguarding engine performance.

References

LECO Corporation. Detection and Quantification of Fatty Acid Methyl Esters (FAMES) in Jet Fuel by GCxGC-TOFMS. Application Note, Form No. 203-821-433, Rev 1, 2013.