Free fatty acids solvent extraction method

Only a very small proportion of the fatty acids are present in the free, unester-ified form and the vast majority are components of other lipids. Nevertheless it is important to be able to measure and identify the free fatty acids present in either form and for this they must be first extracted into an organic solvent and then usually converted to their methyl ester. The simplest method of methyla-tion, which is applicable to both esterified and non-esterified fatty acids, is to heat the lipid sample for 2 h under a current of nitrogen at 80-90°C with 4% sulphuric acid in methanol. After cooling and the addition of water, the resulting methyl esters are extracted several times into hexane and the combined extracts are dried over sodium carbonate and anhydrous sodium sulphate. The solvent fraction is then reduced in volume by a stream of nitrogen. 

Shipe, W. F., Senyk, G. F. and Fountain, K. B. 1980B. Modified copper soap solvent extraction method for measuring free fatty acids in milk. J. Dairy Sci. 63, 193-198. 

Some of the traditional methods used for the characterization of bar soaps are moisture, free acid or free alkalinity, total soap, and chloride (salt). Moisture determinations are typically run by Karl Fischer titration. However, under certain circumstances, moisture can be measured gravimetric ally. The measure of free fatty acid or free alkalinity is typically done via a simple pH titration using phenophtha-lein or potentiometric end point. Total soap is generally done using an extraction/ gravimetric procedure the soap sample is acidified in an ethanol-water mixture, the fatty acids are extracted into a hydrocarbon solvent, and the amount of extracted... 

The seeds contain a pale yellow oil (45-50%) which can be obtained by expelling and subsequent solvent extraction. Commercial oils have a relatively high free fatty acid content (5-20%) depending on the age of the seed and the harvesting methods. The residual meal has a low nutritional value when used in animal feed. The refined oil of good quality melts sharply... 

In the method of Grundy et al. (30) an aqueous homogenate of human feces is made alkaline with 1 M NaOH in 90% aqueous ethanol after the addition of i C-labeled deoxycholic acid. The mixture is refluxed and neutral lipids are removed by petroleum ether extraction. The acidic compounds remaining in the lower phase are next exposed to strong alkaline conditions to hydrolyze conjugated bile acids. After acidification, free bile acids are extracted from the hydrolyzate with chloroform-methanol, 2 1. After solvent evaporation the residue is purified on a Florisil column. After removal of fatty acids, bile acids are eluted with diethyl ether-acetic acid 9 1, v/v. Ethyl acetate and water are added to the bile acid eluate and the lower phase removed. After methylation, the bile acids are separated by pre-... 

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