Triglycerides separation

Figure 7.2.20 Continuous-flow 1 H NMR spectrum (400 MHz) of the triglycerides separated during the extraction process of coffee with supercritical CO2...

Another interesting development in capiUary GC columns is the introduction of new high temperatures metal capiUary column. At the 43rd Pittsburgh Conference Exposition on Analytical Chemistry and Apphed Spectroscopy, 1992, a metal capiUary column for triglyceride separations at temperature up to 370 C was introduced. Diameters of this type of columns are 0.25 or 0.5 mm. The same firm also introduced a similar column for simulated distUlation of hydrocarbons starting at n-pentane. 

Geeraert and DeSchepper pointed out that triglyceride separations obtained by capillary GLC on polar colunms are based predominantly on molecular weight differences (carbon number determinations), while reversed-phase HPLC fractionations (equivalent carbon number separations) are based on the degree of unsaturation of the triglycerides. They also noted that the optimization of HPLC conditions could refine the separations obtained, and proposed an optimized reversed-phase... 

Some separation problems (e.g., triglyceride separation [76]) require a hydrophobic stationary phase and a nonpolar (nonaqueous) mobile phase. This ehromatographic mode is called nonaqueous reversed-phase (NARP) chromatography. The most common commercially available reversed-phase materials are C2, C4, Cg, Cjg, and phenyl phases. 

WCOT columns for triglyceride separations has also been reviewed elsewhere [284,591],... 

To produce highly purified phosphatidylcholine there are two industrial processes batch and continuous. In the batch process for producing phosphatidylcholine fractions with 70—96% PC (Pig. 4) (14,15) deoiled lecithin is blended at 30°C with 30 wt % ethanol, 90 vol %, eventually in the presence of a solubiHzer (for example, mono-, di-, or triglycerides). The ethanol-insoluble fraction is separated and dried. The ethanol-soluble fraction is mixed with aluminum oxide 1 1 and stirred for approximately one hour. After separation, the phosphatidylcholine fraction is concentrated, dried, and packed. 

Distillation. Most fatty acids are distilled to produce high quaHty products having exceUent color and a low level of impurities. Distillation removes odor bodies and low boiling unsaponifiable material in a light ends or heads fraction, and higher boiling material such as polymerized material, triglycerides, color bodies, and heavy decomposition products are removed as a bottoms or pitch fraction. The middle fractions sometimes can be used as is, or they can be fractionated (separated) into relatively pure materials such as lauric, myristic, palmitic, and stearic acids. 

Oils are mixtures of mixed esters with different fatty acids distributed among the ester molecules. Generally, identification of specific esters is not attempted instead the oils are characterized by analysis of the fatty acid composition (8,9). The principal methods have been gas—Hquid and high performance Hquid chromatographic separation of the methyl esters of the fatty acids obtained by transesterification of the oils. Mass spectrometry and nmr are used to identify the individual esters. It has been reported that the free fatty acids obtained by hydrolysis can be separated with equal accuracy by high performance Hquid chromatography (10). A review of the identification and deterrnination of the various mixed triglycerides is available (11). 

Margarine is an example of a solid sample where the materials of interest are soluble in one solvent (in this case methanol) whereas the matrix materials, largely triglycerides, are not. As a consequence, the sample preparation procedure is relatively simple. The chromatographic separation is achieved by using the dispersive interactions between the hydrocarbon chains of the fatty acids and the hydrocarbon chains of a reversed phase. 

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]. 

Nova-Pak C18 column in a methanol water chloroform gradient.92 Choline chloride was added to the mobile phase. One review of techniques used in the analysis of triacylglycerols lists over 300 references on separations of the triglyceride fraction of fats using nonaqueous RPLC, aqueous RPLC, argen-tation chromatography, and other chromatographic methods.93... 

To identify further which substance, cafestol or kahweol, or both, was inducing changes in serum cholesterol, the investigators attempted, but failed due to technical limitations, to separate the two chemical compounds. Alternatively, they compared coffee oil from Arabica vs. Robusta coffee beans. Arabica beans contain both cafestol and kahweol, while Robusta beans contain cafestol, but almost no kahweol. The investigators found that Arabica and Robusta oils both increased serum cholesterol and triglyceride levels comparably. They thus concluded that cafestol is, and kahweol might be, a serum cholesterol raising factor. 

Generally, alkaline saponification in hydroalcoholic KOH is the most widespread approach [11 13]. This allows us to cleave ester bonds and, if necessary, to separate the saponifiable fraction (acids) and unsaponificable fraction (alcohols, sterols, and hydrocarbons). Generally, 3 h of saponification in 10% KOH in water/methanol (3 1) at 60 °C achieves a quantitative yield for triglycerides. Wax esters are less prone to hydrolysis and generally need stronger conditions. Quantitative hydrolysis of beeswax long chain esters has been obtained using 10% KOH in ethanol assisted by microwaves, for 60 min at 80 °C and at 200 W [21],... 

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