Methyl acetates, gas-liquid chromatography

A typical elution profile the separation of saturated esters by gas-liquid chromatography 1. methyl formate 2. methyl acetate 3. ethyl formate 4. ethyl acetate 5. -propyl formate 6. iso-propyl acetate 7. w-butyl formate 8. sec-butyl acetate 9. iso-butyl acetate 10. n-butyl acetate... 

The occurrence of 3-deoxy-D-manno-octulosonic acid in lipopoly-saccharides has prompted its synthesis,537 together with the D-gal-octo158 and the D-gluco analogs.157 Although gas-liquid chromatography was successfully used to analyze the products of these syntheses, it has been reported that methanolysis of a bacterial endotoxin lipopolysaccharide failed to yield 3-deoxy-D-manno-octulosonic acid, presumably because of the lability of the latter to acid.381 However, Kasai and Nowotny have reported four peaks for the O-trimethylsilyl derivatives of 3-deoxy-D-manno-octulosonic acid obtained by methanolysis of the glycolipid from a Salmonella minnesota mutant.538 Reduced 3-deoxy-D-manno-octulosonic acid and its methyl ester have also been analyzed successfully as their acetates.339,539... 

This extension of the Smith analysis, involving methylation of the polyalcohol, has been studied in detail by Bose, both on model systems and on the Ti fructan.84 When a ffuctan is used, this method may give l-hydroxy-3-methoxy-2-propanone and l,3-dimethoxy-2-propa-none, together with methylated glycerols. These compounds may react further under methanolysis conditions to yield 2,5-dimethoxy-2,5-bis(methoxymethyl)-l,4-dioxane and l,3-dimethoxy-2-propanone dimethyl acetal, respectively. Several of these compounds may be obtained from sucrose by a model reaction. In view of the wide variety of hydroxy compounds obtained in this study,84 their separation and identification as benzeneboronates was investigated, and certain of the latter derivatives were purified by gas-liquid chromatography. The characterization of 1,2- and 1,3-diols by the mass spectra of their cyclic benzeneboronates has also been described.634... 

Newsome [6] determined methyl mercury compounds in wheat flour and ground oats by extraction with benzene-formic acid followed by purification and gas-liquid chromatography. Interfering substances were removed from the extracts by column chromatography on silicic acid and partitioning with cysteine acetate solution. The method is sensitive in the 0.01-0.9 ppm range with a recovery of generally better than 95%. 

B. A. Dmitriev, L. V. Backinowsky, O. S. Chizhov, B. M. Zolotarev, and N. K. Kochetkov, Gas-liquid chromatography and mass spectrometry of aldononitrile acetates and partially methylated aldononitrile acetates, Carbohydr. Res., 19 (1971) 432 135. 

Preliminary examinations of dextran structures were conducted by optical rotation, infrared spectroscopy and periodate-oxidation reactions. More detailed results can be achieved by methylation analysis [19]. The hydroxyl groups are methylated with methyl iodide after activation with sodium methylsulfinyl carbanion (Fig. 2). The methyl dextran is hydrolysed to the corresponding different methylated monosaccharides, which are furthermore reduced and peracetylated. The resulting alditol acetates of methylated sugars are separated by gas chromatography and identified by their retention times. In particular, a combined capillary gas-liquid chromatography/mass... 

Methyl Esters. This fraction can be examined first by its behavior on unidimensional thin-layer chromatography. In a solvent system of petroleum ether (30-60°)-diethyl ether-glacial acetic acid (90 10 1, v/v) and using silica gel G (250 p-m) plates, there was only a single spot at Rf 0.65-0.67. This compared exactly with a standard synthetic methyl palmitate. As described in Chapter 4, the chemical nature of the methyl esters can be obtained by analysis on gas-liquid chromatography coupled with mass spectrometry. 

Gas — liquid chromatography has proved a useful analytical technique in carbohydrate chemistry, particularly for methyl ethers and acetic esters. By forming trimethylsilyl ethers of relatively nonvolatile sulfonates of sugars, gas — liquid chromatography can be performed. 

Szczepanik, P. A., Hachey, D. L., and Klein, P. D., Evaluation of Poly S-179 as a stationary phase for the gas-liquid chromatography-mass spectrometry of bile acid methyl ester acetates. /. Lipid Res. 19, 280-283 (1978). 

The application of gas-liquid chromatography td the analysis of nucleosides has been described, and the retention volumes of some nucleoside derivatives are given in Table XIII. Although the free nucleosides are not sufficiently volatile, derivatives in which the hydroxyl or amino groups had been blocked by combinations of acetylation, methylation, or iso-propylidene acetal formation could be eluted successfully. The peaks obtained were well defined and reproducible, although antisymmetrical. 

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