ISO 12966-3:2016 pdf free

ISO 12966-3:2016 pdf free.Animal and vegetable fats and oils一Gas chromatography of fatty acid methyl esters
This part of ISO 12966 specifies a rapid base-catalysed transesterification method for fats and oils with trimethylsulfonium hydroxide (TMSH] 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 (GLC) analysis. It is applicable to all fats and oils, but excluding those coming from milk and milk products.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).
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.
NOTE This part of ISO 12966 is based upon German Standard Method C-VI 11e (98) (see Reference [8]).
The following documents, in whole or in part, are normatively referenced in this document and indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 661, Animal and vegetable fats and oils一Preparation of test sample
The sample is dissolved in tert-butyl methyl ether (TBME) and mixed with a methanolic solution of trimethylsulfonium hydroxide. Glycerides are base-catalysed transesterified and fatty acid methyl esters are formed (see References [4] to [8]). Free fatty acids are converted to salts which are pyrolysed to methyl esters and dimethylsulfide in the injector. Excess reagent is also pyrolysed into methanol and dimethylsulfide. To obtain a complete pyrolytic reaction, a hot injector (split injection) of at least 250 °C is necessary.
For the determination of short-chain fatty acids (C4 to C8), valeric acid methyl ester is used as anin ternal standard. Lipids containing hydroxy groups are partially converted to the corresponding O-methyl ether derivatives which may interfere with fatty acid methyl esters in the GLC separation (Reference [9]). In the early part of the chromatogram (region of C4), peaks may occur, which are from the reagent. These peaks are not taken into account.ISO 12966-3 pdf downlaod.