Preparation of Fatty Acid Derivatives for their Further Analysis and Quantification by Gas Chromatography

Fatty acids are the major component of lipids, and the physical, chemical, and physiological properties of a lipid class depend primarily on its fatty acid composition. The fatty acid composition is determined as the methyl esters of fatty acids by gas chromatography. There are literally dozens of methods for preparing fatty acid derivatives. The generation of fatty acid methyl esters (FAMEs) can be done in acidic or alkaline conditions. The main procedures generally used will be presented in this chapter. The choice of the (trans)-methylation method is highly dependent on the lipid classes present in the sample and on the fatty acid’s nature, i.e., the chain length, the double-bound configuration, and the unsaturation degree. As no single method is suitable for all types of lipids, neither could be use in any circumstances, the objective of this chapter is to give rational information to guide the user in the choice of the appropriate methods for obtaining an accurate fatty acid composition. For further information, see W.W. Christie, in Advances in Lipid Methodology—Two, pp. 69–111 (1993) (Ed. W.W. Christie, Oily Press, Dundee).