Application Book Volume 4 - Biodiesel Quality Control

Significance of the topic

Biodiesel is a key renewable fuel that must meet strict quality standards to ensure engine performance, safety, and regulatory compliance. Analytical control of methanol residue, fatty acid methyl ester (FAME) composition, and glycerol derivatives is essential across the production and blending chain to safeguard product consistency and adhere to European standards (DIN EN 14103, 14105, 14110, 14214).

Objectives and study overview

This application manual demonstrates three routine GC-FID methods for biodiesel quality control:

• Headspace GC analysis of residual methanol (DIN EN 14110)
• FAME profiling and linolenic acid methyl ester quantification for total ester content (DIN EN 14103)
• Derivatization-GC determination of free glycerol, mono-, di-, and triglycerides (DIN EN 14105)

The aim is to achieve high accuracy, reproducibility, and linearity within the specified concentration ranges of each analyte group.

Used instrumentation

• Shimadzu GC-2014AFsc with HT200H headspace autosampler for methanol
• Shimadzu GC-2010AF with AOC-20i autosampler and OCI injection for FAME and glycerides
• Fused-silica capillary columns (Restek Stabilwax-DA, HT5, Biodiesel TG; SGE HT5)
• Flame ionization detector (FID)

Methodology and sample preparation

• Methanol: Heat biodiesel in headspace vials at 60 °C, sample gas phase (500 µL), split 1:10 GC-FID, calibrate in methanol-free FAME with internal standard or without for autosampler.
• FAME: Spike samples with C17:0 as internal standard, inject on polar Restek FAMEWAX, isothermal or ramped oven; quantify total esters and C18:3 component via area summation and relative response factors.
• Glycerides: Use derivatization with MSTFA in pyridine, add two internal standards (1,2,4-butanetriol, tricaprin), extract in n-heptane, inject OCI, separate on high-temperature columns up to 380–400 °C, and quantify groups by internal calibration.

Main results and discussion

• Methanol assay achieved linear calibration (R²>0.9999) over 0.01–0.5 % m/m, detection to 0.01 %, reproducibility ≤1 % RSD—well within DIN EN 14110 limits.
• FAME analysis delivered >99 % total ester with ≤0.06 % RSD and accurate linolenic acid methyl ester (7.6 % m/m) within the 1–15 % specification; iodine value of 109 g I₂/100 g was calculated per EN 14214.
• Glyceride method resolved free glycerol, mono-, di- and triglycerides in <35 min; derivatization and OCI injection ensured reliable peak shapes; total glyceride and free glycerol results met EN 14105 criteria.

Benefits and practical applications

• Automated sample prep and autosampler washing improve throughput and consistency.
• Standardized methods support compliance with fuel specifications and regulatory demands.
• Robust GC configurations allow adaptation to feedstock variability (plant oils, animal fats, used frying oils).

Future trends and applications

• Deployment of fast GC and advanced high-temperature columns for shorter runtimes.
• Integration with laboratory information management systems (LIMS) for seamless data handling.
• Development of miniaturized, field-deployable GC systems and alternative detectors (e.g., MS) for on-site fuel certification.

Conclusion

The described GC-FID workflows deliver high precision, sensitivity, and compliance for biodiesel quality control. Shimadzu’s combination of headspace and on-column injection techniques, together with tailored column chemistries and autosampler automation, ensures reliable analysis of methanol, FAME profiles, and glycerol derivatives. These scalable methods are well equipped to handle evolving feedstocks and meet future regulatory and industrial challenges.

References

• Shimadzu Europa GmbH, Application Book Volume 4: Biodiesel Quality Control (SEG-A-081)