Determination of Oxygenates in Automotive Spark Ignition Engine Fuel according ASTM D7754-11 using

Significance of the Topic

The reliable measurement of trace oxygenates in spark ignition engine fuels is critical for regulatory compliance, process optimization and catalyst protection. Automotive fuels blended with ethanol and other oxygenates must meet stringent purity and concentration limits to ensure engine performance and reduce emissions. Accurate quantification at low ppm levels prevents catalyst deactivation in downstream hydroprocessing and supports quality control throughout the fuel supply chain.

Study Objectives and Overview

This application note demonstrates a rapid, robust approach for determining 14 oxygenates in automotive spark-ignition engine fuel according to ASTM D7754-11. The method covers oxygenate concentrations from 10 to 2000 ppm and ethanol blend levels of 1–15% by volume. The key goals are to optimize analysis time (<30 minutes), maximize sensitivity and repeatability, and eliminate matrix interferences through multidimensional gas chromatography.

Methodology and Instrumentation

A two-dimensional GC setup with Dean’s switch technology (AC Oxytracer) is employed. Key features include:

• Split/Splitless inlet with automated liquid sampler
• Pre-column separation on a methyl silicone column to divert non-oxygenated hydrocarbons
• Timed switching of effluent to analysis column for targeted oxygenate transfer
• Flame ionization detector (FID) for stable, sensitive quantitation
• All carrier flows under electronic pressure control

Internal standard (1,2-dimethoxyethane) ensures quantitation accuracy across 14 compounds: MTBE, ETBE, DIPE, methanol, TAME, n- and i-propanol, n-, i-, sec- and tert-butanol, and tert-pentanol.

Main Results and Discussion

Validation confirms method performance:

• Separation efficiency: Baseline resolution of early eluting peaks (ETBE, MTBE, DIPE)
• Repeatability: Area and retention time RSDs consistently below 1% over 10 consecutive runs at 50 ppm levels
• Linearity: Calibration across 10–1000 ppm (oxygenates) and 1–15% ethanol yields correlation coefficients >0.999
• Recovery: QC check standards at ~30 ppm and ~500 ppm show deviations within ±15% (low range) and ±5% (high range)
• Detectability: Signal-to-noise ratios >5 at 5 ppm confirm reliable detection limits

Benefits and Practical Applications

The AC Oxytracer solution delivers:

• Fast cycle times (<30 minutes) for high sample throughput
• Minimal matrix interference by venting hydrocarbons prior to the analysis column
• High sensitivity and robustness with FID detection
• Compliance with ASTM D7754-11 for regulatory and industrial QC laboratories

Future Trends and Opportunities

Emerging developments may include coupling with mass spectrometric detectors for enhanced compound identification, further automation of sample preparation, and integration of real-time monitoring in blending operations. Advances in column chemistry and valve technology could shorten analysis times and expand the detectable compound range.

Conclusion

The multidimensional GC method using Deans switch technology provides a dependable, high-throughput approach for trace oxygenate analysis in gasoline fuels. It meets or exceeds ASTM D7754-11 requirements, offering excellent sensitivity, repeatability and linearity, thus supporting both regulatory compliance and process optimization.

References