The general method, the boron trifluoride (BF3) method is concerned with the preparation of methyl esters of fatty acids with six or more C atoms, originating from fats, oils and free fatty acids.
The KOH/HCl method is concerned with the preparation of methyl esters of fatty acids with four or more C atoms. This method can also be used for the quantitative determination of fatty acids with a chain length shorter than 10 C atoms in free fatty acid mixtures.
The methyl esters produced can be used for gas-liquid chromatography (GLC).
Unsaponifiable materials are not removed and can, when present in considerable amounts, interfere with the chromatographic analysis.
ISO/TS 17764-2:2002 describes the application of gas chromatography with capillary columns and flame ionization detection for the determination of the content of fatty acids in a fat by making use of the methyl esters of the fatty acids obtained in accordance with the methods specified in ISO/TS 17764-1:2002.