Determination of Methanol Content in Pure Biodiesel (B100) by Headspace-GC in Compliance with EN 14110

Importance of the Topic

Biodiesel (B100) must be free of residual methanol to ensure safe handling and reliable engine performance. Even trace levels of methanol can lower the flash point, compromise seals and elastomers, and impair combustion. Complying with EN 14110 for methanol determination is therefore critical for quality control and regulatory approval.

Study Objectives and Overview

This application note describes the development and validation of a headspace gas chromatography method for quantifying methanol in pure biodiesel. The work aligns with EN 14110 requirements, targeting methanol concentrations from 0.01 to 0.5% m/m and ensuring compatibility with the broader EN 14214 standard limit of below 0.2% m/m.

Methodology and Instrumentation

A Thermo Scientific TRACE GC Ultra system with a split/splitless inlet and flame ionization detector was automated by a TriPlus headspace autosampler. Key analytical parameters included:

• Column: TRACE TR-BIODIESEL(M), 30 m × 0.32 mm ID, 3 µm film
• Carrier gas: Helium at 1.5 mL/min, constant flow
• Oven program: 50 °C (1 min) to 130 °C at 10 °C/min, hold 0.5 min
• Headspace: 80 °C incubation, 40 min equilibration, 500 µL injection

Calibration standards at 0.01, 0.1, and 0.5% m/m were prepared by spiking purified reference FAME with high-purity methanol. Reference FAME was obtained via water extraction and drying over MgSO4 to achieve methanol below 0.001% m/m.

Key Results and Discussion

External calibration delivered excellent linearity (R2 = 0.9999). Analysis of diverse biodiesel samples (rapeseed, soybean, sunflower, and blends) consistently met EN 14214 limits (< 0.2% m/m). Blank injections confirmed no carryover or vial-septum interferences. Repeatability tests (five injections per sample) yielded relative standard deviations below 2%, demonstrating method precision.

Benefits and Practical Applications

This headspace-GC approach provides:

• Automated, high-throughput analysis with minimal sample handling
• Regulatory compliance with European and ASTM biodiesel standards
• Robust detection of low-level methanol for fuel safety and equipment protection

Future Trends and Potential Applications

Advances may include liquid injection with PTV backflush to extend analysis to heavier volatiles, integration with mass spectrometry for multi-component profiling, and real-time monitoring in production lines. Ongoing developments in stationary phases and detector technologies will further enhance sensitivity and expand the scope of biodiesel quality control.

Conclusion

The described headspace-GC method reliably quantifies methanol in B100 biodiesel in full compliance with EN 14110. Its precision, automation, and regulatory alignment make it a valuable tool for laboratories and fuel producers seeking efficient quality assurance.

Reference

• ASTM D6751: Standard Specification for Biodiesel Fuel Blend Stock (B100) for Middle Distillate Fuels.
• EN 14214: Fatty Acid Methyl Esters (FAME) for diesel engines – Requirements and test methods.
• EN 14103: Determination of ester and linolenic acid methyl esters content in FAME.
• Thermo Scientific Application Note AN10212: Total FAME and Linolenic Acid Methyl Ester by GC in compliance with EN 14103.
• EN 14105: Determination of free and total glycerol in FAME.
• ASTM D6584: Free and Total Glycerin in B100 Biodiesel by GC.
• Thermo Scientific Application Note AN10192: Free and Total Glycerin via ASTM D6584.
• Thermo Scientific Application Note AN10215: Free and Total Glycerin in compliance with EN 14105.
• EN 14110: Determination of methanol content in FAME.