Trimethylsilyl ethers determination

Polarimetric analysis of sorbitol and mannitol in the presence of each other and of sugars is possible because of their enhanced optical rotation when molybdate complexes are formed and the higher rotation of the mannitol molybdate complex under conditions of low acidity (194). The concentration of a pure solution of sorbitol may be determined by means of the refractometer (195). Mass spectra of trimethylsilyl ethers of sugar alcohols provide unambiguous identification of tetritols, pentitols, and hexitols and permit determination of molecular weight (196). 

Davison, P. K., Young, R. (1964). Gas chromatography of carbohydrates the quantitative determination ofthe free sugars of plants as their trimethylsilyl ethers. Journal of Chromatography A, 41, 12-21. 

Certain synthetic heptitols that could not be separated by paper chromatography or by electrophoresis have been separated as their O-trimethylsilyl derivatives.404 The procedure of reductive, alkaline hydrolysis, much used in glycopeptide research, yields alditols that have been estimated as their trimethylsilyl ethers,59,405 and D-glucitol in mammalian nerve has similarly been determined.406... 

In model experiments,205 it was found that concentration of an aqueous solution of the aldonic acids in the presence of hydrochloric acid gives exclusively the 1,4-lactones, which, on subsequent trimethyl-silylation, give only one peak on the chromatogram. This method was successfully employed for the separation of D-galacturonic, D-glucuronic, and D-mannuronic acids. Of the 1,4-lactones examined, only the trimethylsilyl ether of D-mannono-1,4-lactone was obtained in crystalline form. However, all of the derivatives showed characteristic differences in their infrared spectra in the range of 1500 to 600 cm"1. When this method was applied to the determination of uronic acids in a variety of polysaccharides,205 it was impossible to find any hydrolytic conditions under which the uronic acids were quantitatively released and then reduced, a problem experienced by other workers.20 The method was, however, successful in affording a qualitative, microscale procedure for the identification of hexuronic acids (which otherwise are difficult to detect). 

Tsai551 has proposed a method for determining the degree of polymerization of oligosaccharides from chitin wherein they are reduced with sodium borohydride, methanolyzed, and the content of 2-acetamido-2-deoxy-D-glucitol determined as the trimethylsilyl ether. 

A particularly attractive approach is summarized in Equation 9.6. Methylation converts any free hydroxyl groups to methyl ethers and the methylated carbohydrates are degraded by acid to mono-and oligomers. The free hydroxyl groups are then chemically modified, as trimethylsilyl ethers for example, the products determined by GLC, mass spectrometry, NMR, and other chemical or physical methods (68). In this manner the linkages (1, 3 in the... 

There are a number of gas chromatographic procedures for the determination of the catecholamines. Methods generally accepted are making the trimethylsilyl ether derivative of the alcoholic group after using diazomethane to prepare the methyl ester and the heptafluorobutyryl derivative. The ethyl esters have been used for the separation of HVA and isoHVA and mass spectrometry applied to study their characterization. 

Trimethylsilyl ethers of asphaltenes were synthesized by refluxing the asphaltene with excess 1,1,1,3,3,3-hexamethyldisilazane (HMDS) in dry tetrahydrofuran (THF). After removal of solvent by rotary evaporation and decanting of the unreacted HMDS, the product was dried under vacuum to constant weight. The number of trimethylsilyl groups introduced by silylation of the asphaltenes was determined by silicon analysis (9). 

All of the calystegines isolated to date have been obtained as amorphous white solids and melting points have therefore not been reported. Structures have been determined by spectroscopic methods, in particular H and 1SC NMR spectroscopy and high-resolution mass spectrometry. Additional confirmatory evidence has been obtained from analysis of the alkaloids as trimethylsilyl ether derivatives by gas chromatography - mass spectrometry (Section 4.4). In certain cases the structures and absolute configurations have been confirmed by synthesis (Section 6). 

With this method, glucose and other sugars (e.g., galactose, fructose, pentose, mannitol, inositol) are determined by GLC of their trimethylsilyl ethers. Urea interferes with the silylation step but is conveniently removed by prior incubation of the urine with urease. A mixed-bed ion-exchange resin is used to deionize the resulting solution. 

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