Fatty acids separation

Separation Techniques. Current methods for separating fatty acids are by solvent crystaUi2ation or by the hydrophili2ation process. Other methods that have been used in the past, or perhaps could be used in the future, are panning and pressing, solvent extraction, supercritical fluid extraction, the use of metal salts in assisting in separation, separations using urea complexes, and adsorption/desorption. 

Armour (2) A process for separating fatty acids by fractional crystallization from acetone. 

Chloroform Benzene (3 1) -do- (/ ) Separated fatty acids and free cholesterols (/ / ) Carried esters to the solvent front. 

Cleary, M.T., Kulprathipanja, S., and Neuzil, R.W. (1985) Process for separating fatty acids from rosin acids. U.S. Patent 4,522,761. 

Table 1 Elution Conditions Used to Separate Fatty Acid Phenacyl Derivatives...

This method is more efficient in the resolution of cis and trans conformational isomers of fatty acids than the usually used GC methods with packed columns, and there are no problems with derivatization of short-chain fatty acids or heat-labile polyunsaturates. Another advantage over GC methods is that the separated fatty acids are not destroyed during their detection, which enables further analysis to be performed. The trans isomers are generally eluted after the corresponding cis isomers. Positioning of the double bonds in the proximity of the carboxy group of an acid usually leads to a shift in the direction of the methyl end of the carbon chain. 

While silver ion liquid chromatography has been utilized to separate fatty acid methyl esters (FAMEs) by number of double bonds and by the configuration (cis/trans) of the double bonds [1-3], the lack of commercial HPLC silver ion columns has limited the impact of this technology. 

Are the primary differences in polarity Partition columns are available that vary in polarity from nonpolar (octyldecyl), through intermediate polarity (octyl and cyanopropyl), to polar (silica). Some columns have similar polarities, but differ in their specificity. Qg and the phenyl column have similar polarities, but Ci8 separates on carbon chain length, while phenyl separates fatty acids on both carbon number and number of double bonds. Phenyl columns also resolve aromatic compounds from aliphatic compounds of similar carbon number. In another example of similar polarities, C8 is a carbon number separator while cyanopropyl selects for functional groups. 

Its temperature range is 20 to 200°C, and it finds use for separating fatty acid methyl esters. 

Fatty acids are usually measured as their methylesters by gas liquid chromatography on packed, capillary or surface-coated open tubular (SCOT), columns with flame ionization detection (Christie, 1982a). HPLC can also be used to separate fatty acid esters with measurement by UV-absorption or fluorescence detection (Christie, 1987). 

The composition of milkfat is somewhat complex. Although dominated by triglycerides, which constitute some 98% of milkfat (with small amounts of diglycerides, monoglycerides, and free fatty acids), various other lipid classes are also present in measurable amounts. It is estimated that about 500 separate fatty acids have been detected in milk lipids it is probable that additional fatty acids remain to be identified. Of these, about 20 are major components the remainder are minor and occur in small or trace quantities (4, 5). The other components include phospholipids, cerebrosides, and sterols (cholesterol and cholesterol esters). Small amounts of fat-soluble vitamins (mainly A, D, and E), antioxidants (tocopherol), pigments (carotene), and flavor components (lactones, aldehydes, and ketones) are also present. 

High-performance liquid chromatography (or less common, high-pressure liquid chromatography, HPLC) is a preferred method of analysis for many compounds because it does not require the high temperatures used in gas chromatography. Separations in HPLC can be based on either a size exclusion or on an adsorption principle. The size exclusion mode is useful for separating fatty acids from... 

Phospholipids are a heterogeneous group of lipids. They mainly consist of phosphatidylcholine (ca. 67%), sphingomyelin (ca. 21 %o), lysolecithin (ca. 7%), and phosphatidylethanolamine (ca. 4%). Each of these constituents has a separate fatty-acid composition, (s. fig. 3.9)... 

In this paper, we describe the apparatus we use to make phase equilibrium measurements on mixtures of conqponents with greatly differing volatilities, putting particular emphasis on recent inqprove-ments over the previous version (6-7). We also describe quantitative measurements of the solubility of methyl oleate in supercritical fluids which can provide a basis for choosing a solvent to separate fatty acids in edible oils. In the following paper (JB.) we explore the utility of cubic equations of state to describe the results of supercritical fluid - liquid phase equilibrium measurements. Some additional experimental results on the mutual solubility of methyl linoleate and carbon dioxide are presented there also. 

Multiple-dimensional TLC is a variant of multiple-development chromatography. For example, in one experiment the chromatoplate was devloped with propanol-ammonia (2 1) which carried fatty acids, cholesterol and then-esters to the solvent front and resolved lecithins and polar lipids. The second run with chloroform-benzene (3 1) separated fatty acids and free cholesterols and carried the esters to the solvent front. The TLC plate was turned at an angle of 180° and developed with carbon tetrachloride which resolved the cholesterol esters. Using more than one plate and the same solvent for the first development but different solvents for the subsequent developments after rotating the plates at an angle of 90°, a large number of amino acids could be successfully resolved. 

The specific organisation is different for each individual pathway, but nevertheless there are some broad generalisations that can be made. First of all, degradation and synthesis are often physically separate. Fatty acids may be both made and used in the same tissue, e.g. liver, but the two directions of metabolism are found in... 

The first reported use of reversed-phase style LC came in 1948 where Boldingh used a rubber powder stationary phase and an acetone and methanol mobile phase to separate fatty acids. The term reversed phase was subsequently coined by Howard and Martin in 1950 with the separation of fatty acids on a paraffin/ -octane stationary phase using aqueous eluents. Because the technique used methods that were opposite to those normally employed, the technique bore the name reversed phase, distinguishing it from the normal-phase separation approach. 

The structure of the surface layers of fatty acid-treated fillers can be quite complex. In the ideal case, one would expect a single layer with all of the acid groups in the carboxylate form and interacting with a basic surface site (i.e., the coating to be in the form of a partial or half-salt, such as M"(0H)C00R). In reality, a variety of other species can be present, including unreacted acid and fatty acid salt not attached to a surface site. In addition, there may be a separate fatty acid/salt phase in the bulk polymer, not associated with the filler surface. The relative importance of these will vary with the application. When multilayers are present, they will be only weakly attached to the surface monolayer. 

A separate fatty acid synthetase system for Cig and Cig fatty acids as well as for the shorter-chain fatty acids. 

MiBE was used as a mobile phase constituent in a system designed to separate the phospholipase-treated molecular species (phosphatidylcholine [PC] and phos-phatidylethanolamine [PE]) found in Ae liver [838]. A column (A = 205 nm) and a 72/18/8/2 acetonitrile/lPA/MlBE/water mobile phase were used. WiAin Ae PC fraction, nine separate fatty acid fractions were separated and identified in 70 min. Similarly for the PE fraction, Ae fatty acids fractions were resolved in 80 min. 

---