Glycerides separation

The test system for the packing was a glyceride separation with acetone and CO2. The results for the Sulzer packings were confirmed by three further systems. 

This value seems rather high. For economical extractions the pressure should be reduced to an optimum value. This can be done by adding entrainers. As an example the pressure for extracting lecithin from soya oil can be reduced from 350 bar with CX>2 to 80 bar by using propane as an entrainer (2). Supercritical extraction should not be restricted to CX>2 as solvent Some separation problems, e.g. the glyceride separation cannot be solved economically with CD2 as a pure extractant Therefore the plant was designed also for other solvents and for the use of entrainers. Design characteristics are ... 

On hydrolysis, fi oils yield a mixture of fatty acids derived mainly from mixed glycerides. Separation of these fatty acids based on molecular wei t or degree of unsaturation is oonoplicated by several factors. First, the relatively small differences in their molecular wei ts make it difficult to separate them by conventional means, particularly v en saturated and xmsaturated fatty acids of the same chain length are to be sqparated. Second, polyunsaturated corpouncls are readily susceptible to polymerization, degradation and/or oxidation, even at moderately elevated tenperatures. 

A shorthand nomenclature is in common use to designate simple glycerides separated in this way the total number of carbon atoms in the aliphatic chains of the compounds (but not in the glycerol moiety) are calculated and this figure is used to denote the compound. As an example, tristearin, triolein and trilinolein are referred to as C54 triacylglycerols or as having a carbon number of 54. 

Figure 8 illustrates one of the processing schemes used for separating various components in a hydrocarbon-containing plant. Acetone extraction removes the polyphenols, glycerides, and sterols, and benzene extraction removes the hydrocarbons. If the biomass species in question contain low concentrations of the nonhydrocarbon components, exclusive of the carbohydrate and protein fractions, direct extraction of the hydrocarbons with benzene or a similar solvent might be preferred. 

The yolk is separated from the white by the vitelline membrane, and is made up of layers that can be seen upon careful examination. Egg yolk is a complex mixture of water, Hpids, and proteias. Lipid components iaclude glycerides, 66.2% phosphoUpids, 29.6% and cholesterol [57-88-5] 4.2%. The phosphohpids consist of 73% lecithin [8002 3-5] 15% cephahn [3681-36-7], and 12% other phosphohpids. Of the fatty acids, 33% are saturated and 67% unsaturated, including 42% oleic acid [112-80-1] and 7% linoleic acid [60-33-3]. Fatty acids can be changed by modifying fatty acids ia the laying feed (see... 

Myristic acid occurs as a glyceride in many vegetable fats and oils, in particular in coconut oil,i its isolation from which involves separation from homologs by fractional distillation of the acids or their esters. The trimyristin obtained from nutmegs 2 (p. 100) or from the seeds of Virola venezuelensis forms the most suitable source. 

FIGURE 13.23 Using the PDA detector and THF at SO C. a comparison of soybean cooking oils provides good separations of the glycerides. 

The concentration of biodiesel (fetty acid methyl esters) and glycerides were analyzed by liquid chromatography (Shimadzu-lOA HPLC). An ODS-2 column (250x4.6mm) was used for the separation. The flow rate of the mobile phase (acetone acetonitrile=l l) was set to 1 ml/min. Peaks were identified by comparison with reference standards. Standards of methyl esters, monoglycerides, digjycerides and triglycerides were bought from Fluka. 

Although not very commonly used in the separation of nentral hpids, two-dimensional systems have been nsed to separate hydrocarbons, steryl esters, methyl esters, and mixed glycerides that move close to each other in one-dimensional systems. Complex neutral lipids of Biomphalaria glabrata have been first developed in hexane diethyl ether (80 20), dried, and the plates have been turned 90°, followed by the second development in hexane diethyl ether methanol (70 20 10) for complete separation of sterol and wax esters, triglycerides, free fatty acids, sterols, and monoglycerides [54]. 

Organic carboxylic acids are commonly found in foods, in the adipate process stream, and as pollutants. Fatty acids are the lipophilic portion of glycerides and a major component of the cell membrane. Phenols are widely used in polymers, as wood preservatives, and as disinfectants. Chloro-phenols such as 4-chlorophenol, two isomeric dichlorophenols, 2,4,6-tri-chlorophenol, three isomeric tetrachlorophenols, and pentachlorophenol were separated on a Dowex (The Dow Chemical Co. Midland, MI) 2-X8 anion exchange resin using an acetic acid-methanol gradient.138... 

Hence, it is possible to measure accurately the integration curve given out by the combined C-l, and C-2 glyceride methylene protons that occurs almost separately at 4. Now, employing these as an internal calibration one may determine conveniently the following two vital informations, such as ... 

The partition of different lipids between two immiscible solvents (countercurrent distribution) is useful for crude fractionation of lipid classes with greatly differing polarities. Repeated extractions in a carefully chosen solvent pair increase the effectiveness of the separation but in practice mixtures of lipids are still found in each fraction. A petroleum ether-ethanol-water system can be used to remove polar contaminants (into the alcoholic phase) when interest lies in the subsequent analysis of neutral glycerides, which may be recovered from the ether phase. Carbon... 

Two-dimensional techniques are usually employed if both phospho-glycerides and glycolipids are present, but it is possible to resolve members of both classes using a diisobutylketone-acetic acid-water mixture (40 25 5). A solvent composed of acetone, acetic acid and water (100 2 1) will separate the mono- and di-galactosyldiglycerides, which are particularly abundant in plant extracts, from phosphoglycerides, which remain at the origin. 

This is a very broad class of compounds commonly used in coatings. Over 400-500 different alkyd resins are commercially available. They are polyesters containing unsaturation that can be cross-linked in the presence of an initiator known traditionally as a drier. A common example is the alkyd formed from phthalic anhydride and a glyceride of linolenic acid obtained from various plants. Cross-linking of the multiple bonds in the long unsaturated chain R produces the thermoset polymer by linking R groups of separate molecules with each other. 

The cross-sections of the saturated acids do not vary much, but the length increases with the number of atoms in the carbon chain, as would be expected from Langmuir s theory. The alcohol has a somewhat greater cross-section than the acids. The cross-section of the glycerides is about three times as great as that of the acids from which they are derived, a fact easily explained on the supposition that the three- acidic chains in each case lie side by side, occupying as much area on the water as if they were in separate acid molecules. 

The solvent extracts can be cleaned up by traditional column chromatography or by solid-phase extraction cartridges. This is a common cleanup method that is widely used in biological, clinical, and environmental sample preparation. More details are presented in Chapter 2. Some examples include the cleanup of pesticide residues and chlorinated hydrocarbons, the separation of nitrogen compounds from hydrocarbons, the separation of aromatic compounds from an aliphatic-aromatic mixture, and similar applications for use with fats, oils, and waxes. This approach provides efficient cleanup of steroids, esters, ketones, glycerides, alkaloids, and carbohydrates as well. Cations, anions, metals, and inorganic compounds are also candidates for this method [7],... 

Carbon dioxide is not very polar, and this characteristic has been a limitation in running polar analytes. Table 2 shows that there are not very many polar chemicals that could be considered for use in the supercritical region. A popular alternative is to add methanol as a modifier to the carbon dioxide. Figure 11.3 shows the effect of adding 1% methanol to the CO2 in the separation of glycerides peak shapes are improved and the retention times are decreased. 

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