Efficiencies of three common lipid extraction methods evaluated by calculating mass balances of the fatty acids

Efficiencies of three common lipid extraction methods have been evaluated by analyzing fatty acids in residues and extracts and calculating the mass balance for the fatty acids. Fatty acids were analyzed by an acid catalyzed direct methylation procedure followed by gas chromatography of fatty acid methyl esters. This procedure was also used as the benchmark for the calculation of mass balances. The three extraction principles investigated were Soxhlet extraction with petroleum ether, Soxhlet extraction after acid hydrolysis, and the Bligh and Dyer method. All samples were dry powders of marine origin; most samples had high ratios of polar to nonpolar lipids. Significant amounts of fatty acids were detected in the residues after extraction. The lowest extraction efficiencies were 30% for the Soxhlet method, 83% for the acid hydrolysis method and 90% for the Bligh and Dyer extraction. The lowest extraction efficiencies were typically found in samples with high ratio of polar to nonpolar lipids.