Determination of 2-EthylHexylNitrate in Diesel Fue ls by Gas Chromatography

Importance of the Topic

Diesel fuel quality and combustion efficiency are critical for modern engines and environmental compliance. 2-Ethylhexyl nitrate (2-EHN) is the most widely used cetane improver, boosting cetane number and overall performance. Reliable quantification of 2-EHN in complex diesel matrices supports refiners and quality control laboratories in meeting regulatory standards and optimizing fuel formulations.

Objectives and Study Overview

This application note describes a robust, sample-preparation-free method for determining 2-EHN in diesel fuels. Key goals include:

• Achieving high sensitivity and specificity in a range of 50–4000 ppm
• Ensuring excellent repeatability and linearity
• Avoiding labor-intensive sample cleanup

Methodology and Instrumentation

The analytical approach employs two-dimensional gas chromatography with Deans heart-cutting:

• Sample introduction via Split/Splitless inlet into a pre-column
• Heart-cut diversion of 2-EHN and co-elutants to a second analytical column
• Separation of 2-EHN from matrix interferences on the second column
• Detection by flame ionization detector (FID)

Main Results and Discussion

Chromatographic performance:

• Complete resolution of 2-EHN from co-eluting diesel components
• Linear detector response over three orders of magnitude (50–4000 ppm) with R² = 0.9999
• Repeatability (n = 10 at 790 ppm): concentration RSD = 0.2%, retention time RSD = 0.04%

These results demonstrate the method’s precision and its suitability for routine diesel analysis without sample pretreatment.

Benefits and Practical Applications

This Deans switch GC-FID method offers:

• High throughput through direct injection of neat samples
• Robust quantification with minimal maintenance
• Wide dynamic range for both low- and high-level 2-EHN monitoring
• Reduced operational costs by eliminating cleanup steps

It is applicable in refinery QA/QC, compliance testing, and research laboratories.

Future Trends and Opportunities

Anticipated developments include:

• Integration with mass spectrometric detection for enhanced specificity
• Automation of heart-cut timing to further improve reproducibility
• Expansion to other cetane improvers and fuel additives
• Adoption of faster columns and advanced stationary phases for reduced analysis time

Conclusion

The described GC-FID method using Deans heart-cutting delivers a sensitive, precise, and linear assay for 2-EHN in diesel without sample preparation. It meets the demands of modern refining and quality control by providing reliable data across a broad concentration range.

Reference

AC Analytical Controls Application Note: Determination of 2-Ethylhexyl Nitrate in Diesel Fuels by Gas Chromatography.