Stearic acid

About: Stearic acid is a research topic. Over the lifetime, 9762 publications have been published within this topic receiving 187487 citations. The topic is also known as: C18:0 & CH3-[CH2]16-COOH.

Gas-liquid partition chromatography: the separation and micro-estimation of volatile fatty acids from formic acid to dodecanoic acid

Abstract: Industry has long used charcoal or other solid absorbents in columns for cleaning gas streams or for solvent recovery, and more recently Turner (1943), Claesson (1946), Glueckauf, Barker & Kitt (1949), Phillips (1949) and Turkel'taub (1950) have used charcoal in gas chromatograms for the analysis of hydrocarbons and esters. Gas-liquid scrubbing columns have been used in industry for many years but, though Martin & Synge (1941) suggested the use of gas-liquid partition chromatograms for analytical purposes, no work has been reported along these lines. This paper presents modifications necessary to the theory of Martin & Synge (1941) to allow for the compressibility of the mobile phase and describes the application ofthe gas-liquid partition chromatogram to the separation of volatile fatty acids. The separations obtainable by this method are essentially parallel to those obtainable by distillation, but good separations can be achieved much more easily and it is possible to work with very much smaller quantities. In fact, the lower limit of quantity of material used is determined only by the efficiency of detection. In general, far less trouble from azeotrope formation is to be expected, since the concentrations of the substances to be separated in the liquid phase are always low and it may be possible to choose a liquid phase which associates only with one component of the azeotrope. Work on a preparative scale, though theoretically possible, is likely to be inconvenient because of the bulk of the apparatus. The method of detection described here is acid-base titration, but many methods of detecting changes in the composition ofa gas stream could be used and it is intended in future publications to explore some of these, which should extend the range of application to all substances capable of being distilled at the pressure of a few mm. of mercury. In suitable cases the gas-liquid partition column has two principal advantages over the ordinary liquid-liquid partition column: (a) the low viscosity of the mobile phase allows relatively longer columns to be used with a corresponding gain in efficiency and (b) in general it is easier to detect changes in composition of a gas than of a liquid stream. A THEORY OF GAS-LIQUID PARTITION CHROMATOGRAPHY

Reference database of Raman spectra of biological molecules

Abstract: Raman spectra of biological materials are very complex, because they consist of signals from all molecules present in cells. In order to obtain chemical information from these spectra, it is necessary to know the Raman patterns of the possible components of a cell. In this paper, we present a collection of Raman spectra of biomolecules that can serve as references for the interpretation of Raman spectra of biological materials. We included the most important components present in a cell: (1) DNA and RNA bases (adenine, cytosine, guanine, thymine and uracil), (2) amino acids (glycine, L-alanine, L-valine, L-serine, L-glutamic acid, L-arginine, L-phenylalanine, L-tyrosine, L-tryptophan, L-histidine, L-proline), (3) fatty acids and fats (lauric acid, myristic acid, palmitic acid, stearic acid, 12-methyltetradecanoic acid, 13-methylmyristic acid, 14-methylpentadecanoic acid, 14-methylhexadecanoic acid, 15-methylpalmitic acid, oleic acid, vaccenic acid, glycerol, triolein, trilinolein, trilinolenin), (4) saccharides (β-D-glucose, lactose, cellulose, D-(+)-dextrose, D-(+)-trehalose, amylose, amylopectine, D-(+)-mannose, D-(+)-fucose, D-(−)-arabinose, D-(+)-xylose, D-(−)-fructose, D-(+)-galactosamine, N-acetyl-D-glucosamine, chitin), (5) primary metabolites (citric acid, succinic acid, fumarate, malic acid, pyruvate, phosphoenolpyruvate, coenzyme A, acetyl coenzyme A, acetoacetate, D-fructose-6-phosphate) and (6) others (β-carotene, ascorbic acid, riboflavin, glutathione). Examples of Raman spectra of bacteria and fungal spores are shown, together with band assignments to the reference products. Copyright © 2007 John Wiley & Sons, Ltd.

Serum cholesterol response to changes in the diet: IV. Particular saturated fatty acids in the diet.

Abstract: For many dietary changes satisfactory prediction of the average change in the serum cholesterol level of man in mg./100 ml., is given by Δ Chol. = 1.35(2ΔS − ΔP) + 1.5ΔZ where S and P are percentages of total calories provided by glycerides of saturated and polyunsaturated fatty acids in the diet and Z2 = mg. of dietary cholesterol/1000 Cal. This formula fails, however, when the dietary change involves large amounts of cocoa butter and discrepancies also appear with beef tallow or hydrogenated coconut oil diets. Controlled dietary experiments at the University of Minnesota and at 2 other centers, provide 63 sets of comparisons of serum cholesterol averages for groups of men on each of 2 chemically characterized diets. Least-squares analysis indicates that stearic acid, as well as saturated fatty acids containing fewer than 12 carbon atoms, have little or no effect on serum cholesterol in man. The equation, Δ Chol. = 1.2(2ΔS′ − ΔP) + 1.5ΔZ, yields good correlation (r = 0.93) with the observed values in these 63 sets of data. This formulation also resolves heretofore puzzling discrepancies in the literature.