ASTM D5441 - Impurities in MTBE

Importance of the Topic

MTBE is a widely used gasoline oxygenate and octane booster. Monitoring trace impurities is critical for fuel performance, regulatory compliance and environmental safety. Robust analytical methods ensure accurate quantification of alcohols, hydrocarbons and ethers present as contaminants.

Objectives and Overview of the Study

The aim of this application note is to demonstrate the separation and detection of common impurities in methyl tert-butyl ether (MTBE) using gas chromatography with flame ionization detection, following the ASTM D5441 protocol. The study outlines optimized conditions enabling baseline resolution of target compounds.

Methodology

• Column: Dimethylpolysiloxane PHAT Phase™ 20M (007-1-20HS-6.0F), 0.18 mm I.D., 6 μm film thickness
• Temperature program: 40 °C (3 min hold), ramp 5 °C/min to 100 °C, then 12 °C/min to 210 °C
• Carrier gas: Helium, 12 psi constant flow
• Injector temperature: 225 °C
• Detector: Flame ionization detector, 300 °C

Used Instrumentation

• Gas chromatograph equipped with FID
• PHAT Phase™ 20M capillary column (007-1-20HS-6.0F)
• Helium supply for carrier gas

Key Results and Discussion

The optimized method achieved clear separation of eleven impurities in MTBE samples:

• Methanol
• 2-Methylbutane
• Pentane
• Cis-2-pentene
• Trans-2-pentene
• 2-Methyl-2-butene
• MTBE
• t-Butyl ethyl ether
• t-Amyl methyl ether
• 2,2,4-Trimethyl-1-pentene
• Cis/trans-2,2′,4,6,6′-pentamethyl-3-heptene

Baseline separation was achieved with sharp peak shapes and good sensitivity, demonstrating compliance with ASTM requirements.

Benefits and Practical Applications

• Reliable quantitation of MTBE impurities for quality control
• Compliance with industry standard (ASTM D5441)
• Efficient analysis suitable for high-throughput labs

Future Trends and Opportunities

• Integration with mass spectrometry for enhanced identification
• Development of shorter, more inert columns for faster analyses
• Green chromatography approaches reducing solvent and energy usage

Conclusion

The presented GC-FID method provides a robust and efficient solution for analyzing impurities in MTBE, meeting regulatory standards and supporting routine quality control in petrochemical laboratories.