Fatty acids derivatization

Mateo Castro R., Domenech Carbo M.T., Peris Martinez V., Gimeno Adelantado J.V., Bosch Reig F., Study of binding media in works of art by gas chromatographic analysis of amino acids and fatty acids derivatized with ethyl chloroformate, Journal of Chromatography A, 1997, 778, 373 381. 

R.M. Castro, M.T. Domenech Carbo, V.P. Martinez, J.V. Gimeno Adelantado, F. Bosch Reig, Study of Binding Media in Works of Art by Gas Chromatographic Analysis of Amino Acids and Fatty Acids Derivatized with Ethyl Chloroformate, J. Chromatography, A, 778, 373 381 (1997). 

Discovery of Insulin Detemir and Liraglutide by Fatty Acid Derivatization... 

Prolongation of the 2-min half-life of native human GLP-1 was achieved through a rational analysis of the structure-activity relationship of numerous fatty acid-derivatized human GLP-1 analogues that showed resistance to DPPIV-mediated inactivation and avoided renal clearance through binding to albumin that exceeds the molecular threshold for glomerular filtration [11]. 

Derivatization of Fatty Acids Derivatized fatty acids have been analyzed to improve ionization and fragmentation characteristics. The FAB spectra of these derivatives are structurally more informative, and fragmentations predominantly occur via CRF processes. One such example is the application of aminoethyl-triphenylphosphonium (AETPP) bromide derivatives to characterize fatty acids structurally by FAB-MS/MS [12]. Other examples include derivatives of aminon-aphthalenesulfonic acid (ANSA), aminobenzenesulfonic acid (ABSA), picolinyl ester, yV-methyl-2-alkylimidazoline (MIM), and dimethyl- (DMAE) and trimethy-laminoethyl (TMAE) esters [8, and references therein], ESI-MS/MS spectra of underivatized and ANSA derivatives of docosahexaenoic acid are compared in Figure 12.8. 

In the United States, the total fat is defined as the total fatty acids expressed as triacylglycerols. Therefore, procedures for releasing fatty acids for total fat determination may be applicable to analysis of fatty acids per se. In the Association of Official Analytical Chemists (AOAC) official method 996.06 (AOAC, 1995), the sample is digested either with hydrochloric acid, to hydrolyze lipids and also carbohydrate and protein with which hpid material may be associated with, or with ammonia for dairy products, in the presence of an internal standard (triundecanoin). The fatty acids are then extracted with a petroleum ether-diethyl ether solvent mixture. As pointed out by Ackman (1999), the potential drawback of using hydrochloric acid is that not all hpids may be hydrolyzed totally to FFA. Presumably, this does not matter if an appropriate fatty acid derivatization procedure for FFA and esterified fatty acids (EFA) is subsequendy employed (see Section 2.3.3.1), as long... 

Glycerides can be analyzed by high-temperature GC on low-bleed columns (Fig. 7). Care should be taken during sample preparation to avoid transesterification. Derivatization is required for good chromatography of free fatty acid and the mono- and diesters, especially if the column is not new. Triesters are not affected by the derivatization reaction. Elution is in the order derivatized fatty acids, derivatized monoesters, derivatized diesters, and triesters (88). 

Eatty acids from commercial fats and oils, such as peanut oil, are extracted with methanolic NaOH and made volatile by derivatizing with a solution of methanol/BE3. Separations are carried out using a capillary 5% phenylmethyl silicone column with MS detection. By searching the associated spectral library students are able to identify the fatty acids present in their sample. Quantitative analysis is by external standards. 

Nitro-bakterien, n.pl. nitrobacteria, -benzol, -benzin, n. nitrobenzene, -chinon, n. nitro-quinone. -cocussaure, /. nitrocoeeic acid, -derivat, n. nitro derivative, -farbstoff, m. nitro dye. -fettkorper, m. aliphatic nitro compound, -fettsaure, /. nitro fatty acid, -gruppe, /. nitro group, -halogenbenzole,... 

GC separation of derivatized carboxylic acids, 46-52 bacterial fatty acids, 51-52 bile acids, 50-51 C6-C24 monocarboxylic acids and dicarboxylic acids, 51 cyano acids, 52 higher-boiling acids, 49 itaconic acid, citraconic acid, and mesaconic acid, 49... 

Gharaibeh, A. A. Voorhess, K. J. Characterization of lipid fatty acids in whole-cell microorganisms using in situ supercritical fluid derivatization/extraction and gas chromatography/mass spectrometry. Anal. Chem. 1996,68,2805-2810. 

Prados P, Fukushima T, Santa T et al (1997) 4-/V,/V-Dimethylam inosu 1 lbnyl-7 -N-(2-aminoethyl)amino-benzofurazan as a new precolumn fluorescence derivatization reagent for carboxylic acids (fatty acids and drugs containing a carboxyl moiety) in liquid chromatography. Anal Chim Acta 344 227-232... 

In the characterization of alkyd resin formulations the palmitic acid to stearic acid (P/S) ratio, often used to identify the type of oil in a binder, cannot be applied as many different oils other than the traditional ones are commonly employed in industrial formulations. Moreover, they are often in mixtures, with the additional complication that fatty acids are also sometime added to the vegetable oils, thus making it impossible to rely on measured P/S values. In any case it is important to always derivatize the samples if Py-GC/MS is used and an alkyd is suspected. Phthalic anhydride will be detected also in an underivatized alkyd pyrogram however, isophthalic acid will not, leading to confusion and the possibility of uncorrected identification [92]. 

Historically, the target analytes in clinical mass spectrometric applications were small, volatile compounds that could be analyzed by GC-MS (see Chapter 4). With time, new chemical preparation techniques and derivatization schemes broadened the scope of these metabolites to include fatty acids, amino acids, intermediates of glucose oxidation, phospholipids, steroids, neurogenic amines, nucleic acids, etc. The molecular weights (molar masses) after derivatization were less than 1000 Da, a mass range easily within the limits of most conventional mass spectrometers. 

Figure 7.3 Derivatization of organic acid and alcohol compounds by diazomethane (CH2N2 top two reactions) by BSTFA (N, O-bis(trimethylsilyl) trifluoroacetamide middle two reactions), and transmethylation of fatty acid esters by saponification using methanolic sodium hydroxide.

Saponification (see Section 7.4) is carried out to extract more recalcitrant lipids, and the yields are higher than for conventional solvent extraction (Stern et al. 2000). 3 ml of 0.5 M methanolic NaOH is added to 0.1 g of the shard powder and heated at 70°C for 3 hours in a sealed glass vial. After cooling, the supernatant is acidified with HC1 and extracted with three aliquots of 3 ml //-hexane. The hexane will not mix with the methanolic solution (unlike the DCM MeOH used above), but will absorb the lipids and can be transferred into a new clean vial. The removal of excess hexane is carried out as above. Saponification will hydrolyze and methylate any ester functionalities, which removes the requirement to derivatize the samples (Section 7.4) unless other molecules are suspected of being present. However, any wax esters or triacylglycerols will also be hydrolyzed to their fatty acid methyl esters and alcohols therefore, if information on their composition is required, then conventional solvent extraction is recommended as a first step. For subsequent characterization of the lipid extract, see Chapter 7. 

Aubert, C. Rontani, J.-F. Perfluoroalkyl Ketones Novel Derivatization Products for the Sensitive Determination of Fatty Acids by Gas GC-MS in El and NICI... 

The compounds analyzed by GC/MS comprise e.g. amino acids [34, 39, 64 - 69], organic acids [33,63,65,66,69], sugars [39,70,71 ], lipids and fatty acids [72, 73]. Moreover, mass distributions of polymers and their building blocks, obtained via hydrolysis of the polymer, were assessed. Examples are glycogen [39, 70], cell protein [8,10,17], or DNA [74]. Most of the analytical methods have been developed for tissue samples. Since most of the compounds studied are polar or even charged molecules, derivatization is necessary in most of the cases of GC/MS analysis. The derivatization method of choice clearly depends... 

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