Measuring Total Naphthalene Hydrocarbons in Aviation Fuels by UV-Vis Spectroscopy

Importance of the Topic

The accurate determination of naphthalene hydrocarbons in aviation fuels is essential for evaluating combustion efficiency, reducing particulate emissions, and ensuring compliance with environmental regulations. Rapid, reliable methods support quality control in fuel production and contribute to safer, more efficient aircraft operation.

Objectives and Overview of the Study

This study demonstrates a streamlined UV-Vis spectroscopic approach to qualitatively and quantitatively measure total naphthalene concentration in Jet A-1 fuel samples. Using the Agilent Cary 3500 Multicell UV-Vis spectrophotometer and Cary UV Workstation v1.6 software, a single-run workflow was established to achieve precise absorbance data collection and automated concentration calculations.

Methodology and Instrumentation

Three Jet A-1 fuel samples were diluted in spectroscopic-grade isooctane and measured in quartz cuvettes with 10 mm pathlength. Spectra were recorded over 240–350 nm with 1 nm bandwidth and 0.1 s signal averaging. End-of-sequence analysis included direct calculation of absorbance at 285 nm and conversion to mass and volume percentages of naphthalenes using user-defined equations within the software.

Used Instrumentation

• Agilent Cary 3500 Multicell UV-Vis spectrophotometer with Peltier temperature control and multicell module supporting up to seven samples simultaneously
• Agilent Cary UV Workstation v1.6 software configured for sequence acquisition, automated calculations, and custom report generation
• Spectroscopic-grade isooctane (2,2,4-trimethylpentane) as solvent control

Main Results and Discussion

Absorbance at 285 nm corresponded to calculated naphthalene volume percentages of 1.00 %, 1.08 %, and 1.36 % for Samples 1–3. Repeatability tests (n = 20) yielded standard deviations of 0.0004–0.0005 Abs, well within acceptance criteria of ±0.18 % to ±0.21 %. Reproducibility across a second instrument and operator also met rigorous precision requirements, with volume variations below ±0.29 %. The integrated workflow eliminated offline data processing and ensured consistent method setup.

Benefits and Practical Use

This UV-Vis method offers high throughput, minimal sample handling, and built-in data analysis, supporting rapid quality assessment of aviation fuels. Automated calculation routines and customizable report templates improve laboratory efficiency and data integrity in QA/QC environments.

Future Trends and Opportunities

Potential advancements include real-time in-line UV-Vis monitoring of fuel streams, extension to other polycyclic aromatic hydrocarbons through spectral deconvolution, and incorporation of chemometric models for enhanced specificity. Miniaturized spectrophotometers and cloud-based data management could further streamline fuel analysis in remote or field settings.

Conclusion

The Agilent Cary 3500 Multicell UV-Vis spectrophotometer combined with Cary UV Workstation v1.6 software provides a robust, user-friendly solution for determining total naphthalene hydrocarbons in aviation fuels. The method delivers excellent precision, reproducibility, and streamlined reporting, making it a valuable tool for fuel quality control and environmental impact assessment.

References

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