Determination of Methanol Content in Biodiesel Using Agilent Select Biodiesel for Methanol

Importance of the Topic

The determination of methanol content in biodiesel is critical to meet European standard EN-14214 requirements and to ensure fuel quality, safety and performance. Low-level methanol affects combustion, engine components and compliance with regulatory limits.

Objectives and Study Overview

This application note presents a method for quantifying trace methanol in fatty acid methyl esters by manual headspace gas chromatography with flame ionisation detection, following EN-14110. It demonstrates the performance of the Agilent Select Biodiesel for Methanol column in separating methanol from other volatiles and discusses method accuracy, precision and suitability for routine analysis.

Methodology

The study employed the internal standard approach using isopropanol added to homogeneous biodiesel samples. A 1 mL aliquot of sample was weighed, spiked with 5 µL isopropanol, sealed in a 20 mL vial and equilibrated at 80 °C for 45 minutes. A 100–200 µL headspace injection was performed using a preheated syringe.

Instrumentation

• Gas chromatograph with manual headspace sampler and split/splitless injector
• Agilent Select Biodiesel for Methanol column, 0.32 mm × 30 m, 3 µm
• Flame ionisation detector at 300 °C
• Helium carrier gas at 80 kPa

Main Results and Discussion

Calibration with three standards (0.0092, 0.0919 and 0.462 % m/m methanol) yielded a linear response (R2 = 0.9996) and an average response factor of 1.18 with coefficient of variation under 15 %. Chromatographic resolution between methanol and potential interferences exceeded Rs = 1.5. Analysis of seven biodiesel samples showed methanol levels from 0.04 to 0.09 %, all below the 0.2 % limit except one low-quality in-house sample at 0.32 %. Blank checks confirmed absence of carryover and interferences.

Benefits and Practical Applications

• Reliable quantification of trace methanol in biodiesel blends
• Compliance with EN-14110 and EN-14214 standards
• Robust separation of low-boiling compounds without interference
• Suitable for quality control and regulatory testing in fuel production

Future Trends and Potential Applications

Advancements may include automated headspace sampling, faster equilibration and injection protocols, coupling to mass spectrometry for enhanced specificity, and miniaturised column technologies for higher throughput. Integration into online monitoring systems could offer real-time quality assurance in biodiesel processing.

Conclusion

The headspace GC-FID method using the Agilent Select column delivers precise, accurate methanol quantification at trace levels, satisfying European regulatory requirements and offering a robust tool for routine biodiesel analysis.

References

• EN-14110 Fat and oil derivatives – Fatty Acid Methyl Esters – determination of methanol content
• EN-14214 Automotive fuels – Fatty Acid Methyl Esters for diesel engines – requirements and test methods