Determination of Ester and Linolenic Acid Methyl Ester Contents in Biodiesel According to EN 14103:2020

Determination of Ester and Linolenic Acid Methyl Ester Contents in Biodiesel (EN 14103:2020) — Nexis GC-2060 Application Summary

Importance of the topic

Biodiesel quality is strongly influenced by the feedstock and processing routes, so reliable, standardized analytical methods are essential for regulatory compliance and ensuring fuel performance and storage stability. Determining total fatty acid methyl ester (FAME) content and the specific linolenic acid methyl ester (C18:3) fraction is required by EN 14103:2020 to confirm product purity and assess susceptibility to oxidative degradation. Robust, cost-effective GC-FID protocols support routine quality control in production and certification laboratories.

Objectives and study overview

This application evaluates the performance of the Shimadzu Nexis GC-2060 (with AOC-30i autosampler) for quantifying total ester content (C6–C24 FAMEs) and linolenic acid methyl ester (C18:3) in biodiesel from rapeseed, soybean and palm oil, following EN 14103:2020. Key goals were to demonstrate compliance with the standard limits, assess repeatability, and compare injection hardware options including a multi-mode injection unit (MMI) versus a conventional split-splitless (SPL) injector.

Methodology

Sample preparation and calculation approach

• 250 mg of homogenized FAME sample was spiked with 100 mg of nonadecanoic acid methyl ester (C19:0) as internal standard and diluted to 10 mL with toluene; 1 μL injected.
• Total ester mass% and C18:3 mass% were calculated from chromatographic peak areas using theoretical FID correction factors (TCFs) relative to the C19:0 internal standard, correcting for ISTD purity and sample/ISTD masses as specified in EN 14103:2020.

Instrumental conditions and data acquisition

• GC: Nexis GC-2060 with AOC-30i autosampler.
• Column: SH-PolarWax, 30 m × 0.25 mm × 0.25 μm.
• Injector: 250 °C, split 1:50 (MMI tested as alternative giving comparable chromatographic results).
• Carrier gas: hydrogen, linear velocity 20.8 cm/s.
• Oven program: 60 °C (2 min) → 10 °C/min → 200 °C → 5 °C/min → 240 °C (16 min); total run ~40 min.
• Detector: FID at 250 °C; detector gas flows at instrument default.

Used instrumentation

The study used the Nexis GC-2060 gas chromatograph equipped with the AOC-30i autosampler. The primary column was SH-PolarWax (30 m × 0.25 mm × 0.25 μm, P/N 227-36305-02). Two injection approaches were evaluated: a conventional split-splitless injector (SPL) and Shimadzu’s multi-mode injection unit (MMI), the latter offering rapid maintenance and comparable performance for this FAME range.

Main results and discussion

Chromatography and quantitative outcomes

• Representative chromatograms were obtained for rapeseed-, soybean- and palm-based biodiesel showing resolved FAME profiles covering the C6–C24 range.
• Measured total ester contents were high for all samples: rapeseed 97.4%, palm oil 97.3%, soybean 97.8% (all > EN requirement of 90% m/m).
• Linolenic acid methyl ester (C18:3) contents were 8.5% (rapeseed), 0.3% (palm), and 7.3% (soybean), all within the EN 14103:2020 acceptable range (1–15% m/m), except that palm is naturally low due to feedstock composition.

Repeatability and standard compliance

• Repeatability was assessed by 12 replicate injections of the same sample, producing %RSD of 0.1% for both total ester and C18:3 determinations, indicating excellent precision.
• The standard repeatability r for ester content in EN 14103:2020 is 1.65. The r for C18:3 is dataset-dependent and can be calculated by the formula r = 0.0092 × (X + 3.9180) where X is the average of the test results; the observed precision was well within these acceptance criteria.

MMI versus SPL injection

• The multi-mode injection unit delivered chromatograms and quantitative results equivalent to the SPL injector across the tested FAME range, while substantially reducing maintenance downtime (from tens of minutes for classical SPL to only a few minutes with MMI).
• Hydrogen proved a cost-effective carrier gas; the Nexis GC-2060 includes appropriate safety features for hydrogen use while maintaining analytical performance.

Benefits and practical applications of the method

The described GC-FID workflow provides a validated, routine-capable approach for biodiesel quality control including:

• Regulatory compliance testing to EN 14103:2020 for ester content and C18:3 specification.
• Feedstock differentiation and process monitoring due to characteristic FAME profiles (e.g., high C18:3 in rapeseed/soybean; low in palm).
• High precision and throughput suitable for production and certification labs; hydrogen carrier gas and MMI option reduce operational costs and downtime.

Future trends and opportunities for application

• Broader adoption of hydrogen as a carrier gas for reduced operating cost, paired with enhanced safety systems and automation.
• Integration of GC-FID screening with GC-MS confirmation for detailed compositional analysis, impurity identification, and trace contaminants.
• Automation and on-line/near-line monitoring in production facilities for real-time quality assurance.
• Method adaptation to emerging feedstocks and blends, and alignment with evolving regulatory requirements for renewable fuels.

Conclusion

The Nexis GC-2060 platform reliably quantifies total ester content and linolenic acid methyl ester in biodiesel according to EN 14103:2020. The method showed excellent precision, met the specification limits for the tested feedstocks, and demonstrated that the MMI injector is a viable, low-maintenance alternative to a conventional split-splitless injector. Using hydrogen as carrier gas enables cost savings without sacrificing performance when appropriate safety measures are in place.

References

1. EN 14103:2020, Fat and oil derivatives - Fatty Acid Methyl Esters (FAME) - Determination of ester and linolenic acid methyl ester contents.

Acknowledgments

The methodology was developed in partnership with Tecosol, Ochsenfurt, Germany. Instrument and trademark acknowledgements apply to Shimadzu Corporation products used in the study.