Optimised preparation of fish tissue samples for the determination of fatty acids by gas chromatography-mass spectrometry

Fatty acids play an important role in the nutrition of fish and in assessing the quality of fish products for human consumption. The usual quantification of fatty acids using gas chromatography-mass spectrometry (GC-MS) requires the extraction and derivatization of fatty acids to fatty acid methyl esters (FAMEs). We compared the yields of fatty acids from liver samples of Oreochromis niloticus and the recovery of the internal standard C23:0 with five different methods for the production of FAMEs: (1) a method based on standard procedures according to EN ISO 12966-2:2017, (2) a modification of the first method with replacement of H 2 SO 4 by HCl for acid-catalyzed methylation, (3) a modification of the first method with use of HCl for acidic methylation and replacement of the solvent isooctane by MTBE, (4) chloroform extraction and subsequent acidic methylation, as well as (5) the rapid method EN ISO 12966-3:2016. The modified standard method according to EN ISO 12966-2:2017 with HCl for acid-catalyzed methylation and the extractant MTBE proved to be the most successful method with the highest fatty acid yields and recovery of the internal standard.