NF EN ISO 5508

ISO 12966-1:2014 gives an overview of the gas chromatographic determination of fatty acids, free and bound, in animal and vegetable fats and oils following their conversion to fatty acid methyl esters (FAMEs).

ISO 12966-2:2011 specifies methods of preparing the methyl esters of fatty acids. It includes methods for preparing fatty acid methyl esters from animal and vegetable fats and oils, fatty acids and soaps. To cover different requirements four methylation methods are specified, namely: a) a "rapid" transmethylation procedure under alkaline conditions; b) a "general" transmethylation/methylation procedure under sequential alkaline and acid conditions; c) a BF3 transmethylation procedure; d) an alternative procedure using acid-catalysed transmethylation of glycerides. Methyl esters so produced are used in various analytical procedures requiring such derivatives, e.g. gas-liquid chromatography (GC), thin-layer chromatography (TLC), and infrared spectrometry (IR).

ISO 12966-3:2009 specifies a rapid base-catalysed transesterification method for fats and oils with trimethylsulfonium hydroxide to prepare fatty acid methyl esters. The method is exclusively applicable to the preparation of methyl esters of fats and oils for gas liquid chromatographic analysis. It is applicable to all fats and oils including milk fat and blends containing milk fat. Isomerization of unsaturated fatty acids only occurs to a minor extent and isomerized fatty acids are only present at the determination limit. As isomerization takes place the procedure is not recommended for conjugated linoleic acid (CLA). As CLA is not correctly analysed, this method is not applicable to the determination of the complete fatty acid composition of milk fat samples. Only about 70 % to 80 % of the free fatty acids are esterified. In the case of conjugated cyclopropyl and cyclopropenyl fatty acids, side reactions may occur, but these do not interfere with the determination of the fatty acids.

ISO 12966-4:2015 specifies a method for the determination of fatty acid methyl esters (FAMEs) derived by transesterification or esterification from fats, oils, and fatty acids by capillary gas chromatography (GLC). Fatty acid methyl esters from C8 to C24 can be separated using this part of ISO 12966 including saturated fatty acid methyl esters, cis- and trans-monounsaturated fatty acid methyl esters, and cis- and trans-polyunsaturated fatty acid methyl esters. The method is applicable to crude, refined, partially hydrogenated, or fully hydrogenated fats, oils, and fatty acids derived from animal and vegetable sources. This method is not suitable for the analysis of dairy, ruminant fats and oils, or products supplemented with conjugated linoleic acid (CLA). Milk and milk products (or fat coming from milk and milk products) are excluded from the scope of this part of ISO 12966. ISO 12966-4:2015 is not applicable to di-, tri-, polymerized and oxidized fatty acids, and fats and oils.