Automated Determination of Fatty Acid Methyl Ester and Cis/Trans- Methyl Ester Composition of Fats and Oils

Importance of the Topic

Accurate profiling of fatty acid methyl esters (FAMEs), including cis/trans isomer content, is critical in food quality control, nutritional studies and industrial process monitoring. Automating sample preparation and analysis enhances throughput, reduces human error and supports 24-hour uninterrupted operation, meeting the growing demand for high-volume, reliable fat and oil characterization.

Objectives and Study Overview

This study presents a fully automated workflow for derivatizing lipid samples to FAMEs and assessing their cis/trans composition by gas chromatography with flame ionization detection (GC-FID). It compares the standard manual boron trifluoride (BF₃) method with an automated sodium methanolate (NaOCH₃) approach, aiming to streamline laboratory operations and maintain analytical performance.

Methodology

• Weigh lipid extracts into autosampler vials and load onto the Focus robotic platform.
• Add n-heptane solvent and mix to dissolve lipids.
• Introduce sodium methanolate for in-situ transesterification and shake.
• Allow phase separation; robot withdraws clear FAME-containing layer.
• Inject aliquots directly into GC-FID for analysis.

Instrumentation

• Optic 2-200 programmable injector
• Focus sample preparation robot
• Agilent 6890 GC coupled to an FID detector
• CP-Sil 88 capillary column (100 m × 0.25 mm i.d. × 0.4 µm film)

Main Results and Discussion

Comparative chromatograms reveal equivalent resolution of saturated, monounsaturated and polyunsaturated FAMEs between manual and automated procedures. The automated NaOCH₃ method delivers clear baseline separation of key components (e.g. C16:0, C18:1 cis/trans, C20:5, C22:6) without generating interfering by-products. Peak shapes and retention times match those obtained with the BF₃ protocol, validating the new workflow’s analytical integrity.

Benefits and Practical Applications

• Unattended 24-hour operation accelerates sample throughput and reduces analyst workload.
• Elimination of hazardous BF₃ reagent handling improves laboratory safety.
• Consistent, automated derivatization enhances reproducibility for QA/QC in food and feed industries.
• Adaptable to diverse fat and oil matrices, including complex nutritional samples.

Future Trends and Opportunities

Integration of automated transesterification with high-throughput GC-mass spectrometry or multidimensional chromatography may expand structural elucidation of minor lipid species. Further advances in robotics and smart scheduling could enable simultaneous multi-method assays, supporting comprehensive lipidomics. Green chemistry developments may introduce even milder catalysts for safer, faster derivatization.

Conclusion

The fully automated NaOCH₃-based sample preparation delivers robust FAME and cis/trans isomer analysis comparable to manual BF₃ methods while offering higher throughput, improved safety and reduced labor. This approach is ideally suited for routine fat and oil quality control in research and industrial laboratories.

Reference

• Sjaak de Koning, Application Note No. 061: Automated Determination of Fatty Acid Methyl Ester and Cis/Trans-Methyl Ester Composition of Fats and Oils, GL Sciences B.V.