Liquid chromatography-mass spectrometry acid derivatives

Total fatty acids were liberated by subjecting Salmonella minnesota Re lipopolysaccharide (or free lipid A) to acidic (4 N HC1, 5 h, 100°C) followed by alkaline (1 N NaOH, 1 h, 100°C) hydrolysis. After extraction (chloroform), the free fatty acids were converted into their methyl esters (diazomethane) and analysed by combined gas-liquid chromatography/mass spectrometry. Alternatively, the fatty acids of lipid A are transesterified by treatment of lipopolysaccharide with methanolic HC1 (2 N HC1 in water-free CHaOH, 18 h, 85°C). By these procedures the following fatty acids were identified (in approximate amounts relative to 2 moles glucosamine) dodecanoic (12 0, 1.1 mole), tetradecanoic (14 0, 0.8 mole), hexadecanoic (16 0, 0.9 mole), 2-hydroxytetradecanoic (2-OH-l4 0, 0.1 mole), and 3-hydroxytetradecanoic acid (3-OH-14 0, 4 moles). In total, therefore, approximately 7 moles of fatty acids are present per mole of lipid A backbone. The stereochemistry of the hydroxylated fatty acids was determined by gas-liquid chromatography of their diastereomeric methoxyacyl-L-phenylethylamide derivatives (24). It was found that 2-hydroxyte-tradecanoic acid possesses the-Ts), and the predominating 3-hydroxytetradecanoic acid the (R) configuration. 

Lee SH, Oe T, Arora JS, Blair lA. Analysis of Fe-II-mediated decomposition of a linoleic acid-derived lipid hydroperoxide by liquid chromatography/mass spectrometry. J Mass Spectrom. 2005b 40 661—668. 

Liquid chromatography-mass spectrometry (LC-MS) is also becoming an increasingly popular analytical tool. Derivatives employed for LC analysis with UV or fluorescence detection have also been studied by LC-MS. It is particularly useful for the identification of rare amino acids and verification of peak purity. 

See also. Analytical Reagents Specification. Derivat-ization of Analytes. Fluorescence Derivatization Fluorescence Labeling Quantitative Anaiysis. Lipids Fatty Acids. Liquid Chromatography Liquid Chromatography-Mass Spectrometry Pharmaceuticai Applications. Mass Spectrometry Forensic Appiications. Spectrophotometry Derivative Techniques. 

From 1966 to 1986 Horning was Director of the Institute of Lipid Research, Chairman of the Biochemistry Department (1962-1966), and Professor of Chemistry at Baylor College of Medicine (1961-1986). During this period he applied gas chromatography to steroids in human fluids, urine, bile and spinal liquids, and to amino acid derivatives. His group isolated acids, alcohols, and waxes from human skin. Here they applied mass spectrometry and liquid or gas chromatography to the identification of numerous human substances. They extended these techniques to investigations of the metabolism of many different compounds in humans. 

Aminosalicylic acid in assessment of reactive oxygen species formation by in vitro Fenton and ozonation reactions and by in vivo ozone-exposure experiments in rats revealed oxidation products as follows salicylic acid, by deamination 2,3-dihydro-xybenzoic acid and 2,5-dihydroxybenzoic acid, from radical or enzymatic hydroxylation 5-amino-2 - hydroxy-N,W-bis(3 - carboxy- 4- hydroxyphenyl)-1,4-benzoquinonediimine, a condensation product of oxidised 5-aminosalicylic acid and 5-amino-2,3,4,6-tetrahydroxybenzoic acid, attributed to hydroxyl radical attack without deamination, identified by high-pressure liquid chromatography electrochemical detector system analysis and by gas chromatography-mass spectrometry analysis of trimethyl silyl derivatives (Kumarathasan et al. 2001). 

In most respects, the standard approach taken to analyze the fatty acids of functional foods is similar to that for conventional foods. The steps are to extract the total lipids or fatty acids, convert the fatty acids to a suitable derivative (often to fatty acid methyl esters (FAME)), and analyze the derivatized fatty acids by a suitable chromatographic technique, usually GC with flame ionization detection (FID), Other chromatographic techniques, including gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC), may be required. Nonchromatographic techniques such as infrared (IR) spectroscopy may be used in some simations, perhaps because of the speed of analysis. 

Great progress in our knowledge about sialic acids was made with the aid of gas-liquid chromatography (g.l.c.), mass spectrometry (m.s.), and n.m.r. spectroscopy. Structural analysis of the many different N- andO-acylated Neu derivatives occurring in Nature will be described in Sections IV,5 and 6. 

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