Analysis of Fatty Acid

Fatty acids commonly occur in lipid extracts, where they exist in both free and esterified forms. Free fatty acids are isolated along with the neutral lipids. The esterified fatty acids can be released via hydrolysis of lipids. Negative-ion FAB and ESI are the most suitable modes of ionization for fatty acids. In combination with CID, a wealth of structmal information has been gathered by using these two modes of ionization for fatty acids and other lipid species. Electron ionization (EI)-MS has also been one of the successful mass spectrometric 

coupled with low-energy CID, although structurally less informative, can provide important structure-related data for polyunsaturated fatty acids [10] and polyhydroxy unsaturated fatty acids [11]. Fragmentation is directed by the position of the hydroxy group or a double bond. As a consequence, isomer-specific CID spectra are produced. 

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Styrene-degrading bacteria from full-scale and experimental biofilters were exposed to [ HJstyrene, and analysis of fatty acids was used to distinguish the bacterial flora of the two systems (Alexandrino et al. 2001). 

Quantitative estimates of microbial and community structure by means of analysis of the phospholipid fraction have been performed on. sediments, water (135), and dust (136) as well as. soil (137-141). The method is applicable to the study of mixed populations of varying degrees of complexity and is relatively straightforward to perform. A selection of studies involving the analysis of fatty acid profiles of environmental samples are outlined in Table 6. 

G. Chiavari, D. Fabbri and S. Prati, Effect of pigments on the analysis of fatty acids in siccative oils by pyrolysis methylation and silylation, J. Anal. Appl. Pyrol., 74, 39 44 (2005). 

Patrick, M., Koning, A. J. and Smith, A. B. (1985) Gas liquid chromatographic analysis of fatty acids in food residues from ceramics found in the Southwestern Cape. Archaeomtery 27, 231 236. 

Earlier analytical results from the gas chromatographic analysis of fatty acids seemed to be very high. Williams [102] repeated much of the early work, using extreme care in the avoidance of contamination, and found very much smaller quantities. Papers concerned with the fatty acid content of the water column and sediment include [ 103-109]. 

Meier-Augenstein, W. (2002). Stable isotope analysis of fatty acids by gas chromatography-isotope ratio mass spectrometry. Analytica Chimica Acta 465 63-79. 

For the analysis of fatty acids amide-linked to GlcN(I), several chemical degradation procedures are available. One comprises periodate oxidation of 0-deacylated and 2H-reducedlipid A (lipid A-OH ). Following permethyl-ation, g.l.c.-m.s. analysis revealed a 2-deoxy-1 -deuterio-1,3-di-O-methyl-2-(iV-methyl-3-methoxyacylamido)glycerol derivative in which the amide-finked fatty acid at GlcN(I) was identified as 14 0(3-OH) in B. pertussis (93), and as 16 0(3-OH) and 18 0(3-OH) in R. trifolii 81). 

Petersson, M. A., Hulthe, G., and Fogelqvist, E. (1999). New sheathless interface for coupling capillary-electrophoresis to electrospray mass-spectrometry evaluated by the analysis of fatty acids and prostaglandins./. Chromatogr. A 854, 141 — 154. 

A very polar phase such as carbowax is generally only used for samples requiring a high degree of polar discrimination for adequate separation or retention. An example of this is in the analysis of fatty acids with differing degrees of unsaturation. On a non-polar column such as BPX-5, a series of C-18 acids such as stearic, oleic, linoleic and linolenic acids, which contain respectively 0, 1,2 and 3 double bonds, overlaps extensively. However, on polar columns such as carbowax they are separated. 

Lawi-Berger, C. and I. Kapetanidis. Chemotaxonomic study of cannabis (Cannabaceae). Part 2. Quantitative analysis of fatty acids in hemp seeds of Cannabis sativa L. Pharm Acta Helv 1983 58(3) 79-81. 

Christie, W.W. (1998) Gas chromatography-mass spectrometry methods for structural analysis of fatty acids. Lipids 33, 343-353. A detailed description of the methods used to obtain data such as those presented in Figure 10-24. 

The application of several chromatographic procedures to the separation and identification of milk lipids was mainly responsible for these endeavors. The first gas-liquid chromatographic (GLC) analysis of milk fatty acids was published by James and Martin (1956). By 1960, many laboratories were using GLC for routine analysis of fatty acids. For example, Jensen et al. (1962) reported the fatty acid compositions of 106 milk samples taken during 1 year. In comparison, Hansen and Shorland (1952) analyzed only six samples in a year, using distillation of methyl esters. 

Strocchi, A. and Holman, R. T. 1971. Analysis of fatty acids of butter fat. Riv. Ital. Sostanze Grasse 48, 617-622. 

Tail reducers are polar substances added in small quantities along with the stationary phase, and are used most frequently with nonpolar phases. Phosphoric acid is used with polyesters(7) for analysis of fatty acids and has been found effective for... 

D1.2 Analysis of Fatty Acids in Food Lipids Basic Protocol 1 Preparation of Fatty Acid Methyl Esters from Lipid Dl.2.1... 

Analysis of Fatty Acids in Food Lipids Equation D1.2.1... 

Sample preparation is probably the most important step in any analytical procedure. Poor preparation of lipid samples will only yield inferior or questionable results. Some commonly performed sample-preparation procedures for gas-liquid chromatographic (GC) analysis of fatty acids in food samples are introduced in this unit. Since the introduction of gas chromatography in the 1950s, significant progress has been made in fatty acid analysis of lipids however, fatty acid methyl esters (FAMEs) are still the most commonly used fatty acid derivative for routine analysis of food fatty acid composition. 

The column is the most critical part of a GC system and is chosen based on the nature of the analysis. There are two types of columns available for GC analysis packed columns and capillary (e.g., wall coated open tubular WCOT) columns. A packed column is not the primary choice for today s routine analysis of fatty acid composition due to its low resolution and requirement for large amounts of sample. Compared to a packed column, a capillary column needs far less sample and is able to achieve superior resolution. 

Bannon, C.D., Craske, J.D., Hai, N.T., Harper, N.L., and O Rourke, K.L. 1982. Analysis of fatty acid methyl esters with high accuracy and reliability. II. Methylation of fats and oils with boron tri-... 

If the analysis of fatty acid methyl esters gives a large amount of information on the composition of fats, there remain some unsolved problems, related to the two major flaws of the approach. The transesterification of TGs derived from polyunsatured acids is not always quantitative. A more important and general problem is that the method does not provide any information regarding the actual composition of the TGs. 

Their study agrees with the Myher et al. (130) estimation in the identification of TGs with odd-carbon-number fatty acids (CN = 15 and 17), either branched or linear. However, they have been able to differentiate between iso and anteiso isomers not only in the GLC analysis of fatty acids but also in TG estimation. Tridecanoic and nonadecanoic acids were identified by GLC but were not included in TG estimation due to their low amounts in whole milk fat content. 

On comparing the chemical composition of hydrocarbons and fatty oils, a certain parallelism between these two groups of products is found. Actually the difference is only due to the presence of a relatively small amount of oxygen in the esters. Thus, in principle, the structural analysis of fatty acid derivatives can be carried out by removing the oxygen and transforming the products into saturated hydrocarbons of... 

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