Determination of the identity of by‐products in the industrial production of saturated fatty acids

A technical product of saturated fatty acids has been analyzed to determine the structure of by‐products found in the C20–22 fatty acids manufactured from fish oil. Short‐path distillation of the weakly colored product provided a residue, which was extracted either by supercritical carbon dioxide or by acetone. Extracts and residues were analyzed by size‐exclusion chromatography, supercritical fluid chromatography, and by gas chromatography, the latter combined with mass spectrometry and Fourier‐transform infrared spectroscopy, and by nuclear magnetic resonance spectrometry. A series of homologs of fatty acid dimers was identified as lactone esters. Each homolog also contained several isomers with a varying number of carbon atoms in the two hydrocarbon chains of the dimers. Trimers, containing yellow components, were also present in small amounts, but the structure of the trimers has not been determined yet.