Triglycerides, analyzers

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. 

The standard analytical methods for biodiesel methyl ester are time-consuming and often require multiple physical analyzes per sample. NIRS allows for the simple set up of calibrations for multiple important biodiesel qualities such as mono-, di- and triglycerides, residual methanol, glycerol and moisture as well as... 

Fasted blood samples have to be analyzed for this analysis. When non-fasting samples are analyzed, the triglyceride-rich chylomicrons will be included in the VLDL fraction during this procedure, which will lead to false results. 

Chromarod FID peaks of sterols, diglycerides, monoglycerides, and polar lipids are narrower and sharper than peaks of triglycerides and free fatty acids when analyzed using either method described in this unit (see Basic Protocol and Alternate Protocol). Hydrogenation of total lipids (see Support Protocol) results in much sharper and narrower peaks, which in turn substantially improves the resolution between lipid classes. The accuracy and precision in quantitating lipid classes of vegetable oils and animal fats are expected to be better than those from marine lipids. 

Zeman and Scharmann (57) reported the presence of 0.3% nonpolar dimers composed of diunsaturated bicyclic and tetraunsaturated acyclic structures in peanut oil subjected to thermal and oxidative action. Perrin et al. (58) analyzed samples from two different peanut and sunflower oils oxidized by deep fat frying to a stable foam formation. They reported the presence of dimers at levels between 12.1 % and 12.9% of the oxidized mixtures. Peanut oil oxidized by deep fat frying before and after stable foam formation yielded 7.8% and 14% dimers, respectively. Gere et al. (59) reported nonpolar and polar dimeric triglycerides in sunflower oil used in deep fat frying. 

The IUPAC Commission on Oils, Fats and Derivatives undertook the development of a method and collaborative study for the determination of triglycerides in vegetable oils by liquid chromatography. Three collaborative studies were conducted from 1985 to 1987. Refinements were made in the method after the first collaborative study, and the second and third collaborative studies demonstrated that the method produces acceptable results. Materials studied were soybean oil, almond oil, sunflower oil, olive oil, rapeseed oil, and blends of palm and sunflower oils and almond and sunflower oils. Six test samples were analyzed by 18 laboratories from 11 countries in the second study 4 test samples were analyzed by 16 laboratories from 12 countries in the third study. The method for the determination of triglycerides (by partition numbers) in vegetable oils by liquid chromatography was the first action adopted by AOAC INTERNATIONAL as an IUPAC-AOC-AOAC method (103). 

Table I summarizes the various meats, meat constituents, and other related substances which have been analyzed, including substances reported on previously (6) as well as those for which new data are given. The substances chosen are intended to provide a cross-section of the type of inherently related material from which volatile irradiation odor and flavor compounds might be expected to form. Thus, in addition to several whole meats, the volatile irradiation products from a number of protein and lipid substances have been analyzed. Among the lipid substances included are typical whole fats and separate moieties such as triglycerides, fatty acid esters, and cholesterol, as an example of a steroid. Among the proteinaceous substances included are a protein, a polypeptide, and some individual amino acids. Finally, beef itself has been separated into a protein, a lipid, and a lipoprotein fraction, and these have been separated, irradiated, and analyzed.

A typical full workup of major components of blood serum on a hospital analyzer reports about 20 concentrations, among them protein (both the total amount and some major subcategories such as albumin), cholesterol and several related quantities (triglycerides, high- and low-density lipoproteins), glucose, bilirubin, and several ions. Many of these, as will be discussed below, have sufficiently strong Raman signatures that they can be detected in a Raman spectrum acquired on the scale of a minute. 

The milk sample was hydrolzyed and extracted as described in the experimental section. The hexane extract was then analyzed for the presence of neutral, nonpolar cannabinoids, (A and A -THC, CBN, CBN). Breast milk contains 2-6% fats, the exact content varying with maternal diet. Hexane extracts a large amount of fat from the milk, making analysis of trace cannabinoids in this matrix difficult. Triglycerides, the major lipid components of milk, are difficult to elute from reverse phase columns and thus a normal phase separation was used for the milk extract. 

Najera, A.I., Perea, S., Barcina, Y., de Renobales, M. and Barron, LJ.R. (1999) A reverse-phase high performance liquid chromatographic method for analyzing complex mixtures of triglycerides. Application to the fat fraction of an aged cheese. J. Am. Oil Chem. Soc., 76, 399-407. 

Using a lipase-immobilized membrane, the FET biosensor made it possible to analyze for triglycerides (7,13,26). Lipase catalyzes the hydrolysis of triglyceride into glycerol and oig anic acid. In an assay for tributylin the FET biosensor gives... 

A major question to address in the future is how structure influences the dynamics of digestion and the signaling processes involved. Armand et al. (1996, 1999) investigated the digestion and lipid absorption from emulsions with different droplet sizes in humans. Healthy subjects received intragastrioally a coarse (10 pm) and a fine (0.7 pm) lipid emulsion of identical composition in random order. Gastric and duodenal aspirates as well as triglyceride appearance in the blood were analyzed. They found an increase in droplet size in the stomach however, the fine emulsion retained droplets... 

Fatty Acid Composition. Ohve oil triglycerides are converted into methyl esters, and the methyl esters are analyzed by gas-liquid chromatography (GLC) (70, 71). The limits of genuine olive oil are as follows (% m/m) (12) ... 

Saturated Fatty Acids in Position 2 of the Triglycerides. Hydrolysis with pancreatic lipase is followed by thin-layer chromatographic isolation of the monoglyceride fraction, which is converted to methyl esters. The methyl esters are analyzed... 

---