EN 15779 Determination of Polyunsaturated (≥ 4 double bonds) fatty acid methyl esters (PUFA)

Importance of the Topic

Biodiesel is a renewable alternative to petroleum diesel and its quality is strictly regulated to ensure engine performance and fuel stability. Polyunsaturated fatty acid methyl esters (PUFA, ≥4 double bonds) are particularly prone to oxidation and polymerization, leading to potential fouling of engines, filters and fuel lines. Accurate quantification of PUFA content in fatty acid methyl ester (FAME) samples is therefore essential to meet standards and guarantee long-term fuel reliability.

Study Objectives and Overview

This application note presents a fully compliant method for determining the combined content of the four most prevalent PUFA methyl esters (C20:4 n-6, C20:5 n-3, C22:5 n-3, C22:6 n-3) in FAME, following the European Standard EN 15779:2009. The study demonstrates method performance, including repeatability and accuracy, using reference samples spiked to target levels around 1 % total PUFA.

Methodology and Instrumentation

After adding a C23:0 internal standard solution in heptane, samples are introduced via a split/splitless inlet. Separation is achieved on a polyethylene glycol (wax) capillary column under a two-step temperature program in a dual programmable oven. Detection is performed by flame ionization (FID) and quantification uses internal standard calibration with theoretical response factors specified in EN 15779.

Main Results and Discussion

Chromatograms of pure PUFA reference mixtures, marine biodiesel (≈16 % PUFA) and rapeseed biodiesel spiked to ~1 % PUFA illustrate clear resolution and accurate retention times. Repeatability tests on rapeseed matrix yielded an average total PUFA of 1.091 % with an RSD of 0.15 %, and individual PUFA RSDs below 0.30 %. System repeatability far exceeds the method requirement of 0.07 % absolute.

Benefits and Practical Applications

• Full compliance with EN 15779:2009 for PUFA quantification
• Integrated QC materials and dedicated reporting software for biodiesel analysis
• Dual oven design allows rapid switching between methods without column changes
• Applicability to related standards (EN 14103, EN 14105, EN 14110, prEN 16300, ASTM 6584)

Future Trends and Potential Applications

As the industry shifts toward algae-derived biodiesel and novel feedstocks, rapid and robust PUFA determination remains critical. Future enhancements may include coupling gas chromatography with mass spectrometry for increased selectivity, automation of calibration routines, and extension of the method to additional unsaturated lipid classes.

Conclusion

The AC Biodiesel All in One solution delivers precise, reliable and standards-compliant quantification of PUFA methyl esters in biodiesel. It offers laboratories a user-friendly platform for routine quality control and flexible operation across multiple FAME analysis methods.

Instrumentation Used

• Gas chromatograph with split/splitless inlet and dual programmable oven
• Polyethylene glycol capillary column (30 m × 0.25 mm × 0.25 µm)
• Flame ionization detector (FID)
• Internal standard: methyl tricosanoate (C23:0) in heptane
• Automated liquid sampler

Reference

• EN 15779:2009 Determination of polyunsaturated (≥4 double bonds) fatty acid methyl esters
• EN 14214: FAME specifications for biodiesel fuel
• ASTM D6751: Standard specification for biodiesel fuel blend stock