Trimethyl silyl derivatives

Plasma and urine levels of the drug are determined by chromatographing the trimethyl-silyl derivative of dobutamine on a 6-foot column packed with 3.0% UC-W98 silicon gum rubber (methyl-vinyl) on Diatoport S operated at 260°C. The hydrogen flame detector is maintained at 280°C. Helium flow rate is 60 ml/min. The retention time of dobutamine derivative (TMS) under these conditions is 3.8 minutes. This method measures plasma levels as low as 1 ig/ml (4). 

Krauss, D. Mainx, H.G. Tauscher, B. Bischof, P. Fragmentation of Trimethyl-silyl Derivatives of 2-Alkoxyphenols a Further Violation of the Even-Electron Rule. Org. Mass Spectrom. 1985, 20, 614-618. 

Although many analyses are performed on alditol acetates (see Section VII, p. 56), in order to avoid the formation of multiple peaks, such a reduction is not practical when the mixture contains ketoses, notably fructose. Such analyses are mainly encountered with medical samples and in the examination of sugars occurring free in Nature. Furthermore, the peak-area ratios may be used as a means of identification, to check on the completeness of trimethylsilylation,67,89 and, despite the complex chromatograms obtained from trimethyl-silyl derivatives, they have the merit of being rapidly formed.89 For all of these reasons, improvements in the separation of monosaccharides as their trimethylsilyl derivatives continue to be of considerable importance. 

The separation and identification of disaccharides is often an important step in the elucidation of the structure of a natural polysaccharide, and Percival484 has published useful data on the O-trimethyl-silyl derivatives of a variety of disaccharides and their reduction products. In some instances, the trimethylsilyl ethers of the disaccharide alditols have lower retention times than those of the disaccharide derivatives. The per-O-trimethylsilyl derivatives of gentiobi-itol and maltitol were encountered in studies on the structure of Pneumococcus Type II capsular polysaccharide.4843... 

Formyl-2-methylfuran was converted in 75% yield into derivative 319 by electrolytic methoxylation. A corresponding mixture of cis-diols (320) was treated with Dowex W-50 ion-exchange resin in methanol for four days, to afford 5-deoxy-3-C-(dimethoxymethyl)-DL-eryf/rro-4-pentulose dimethyl acetal (321). Reduction of this compound with lithium aluminum hydride or sodium borohydride gave a mixture of 5-deoxy-3-C-(dimethoxymethyl)pentoses, which was separated by column chromatography on silica gel, to give206 DL-streptose tetramethyl acetal (322) and the isomeric 5-deoxy-3-C-(dimethoxy-methyl)-DL-ribose dimethyl acetal 323 (hjxo ribo = 13 7). Detailed, combined gas-liquid chromatographic-mass spectrometric analysis of the compounds related to streptose (in the form of their trimethyl-silyl derivatives) has been described.207... 

Simultaneous Determination of Acids. With the advent of trimethyl-silyl derivatives of the organic acids, GLC determination has been developed (60, 95) as a method for their detection and quantitative determination. 

When samples of a pure glucose anomer were dissolved in water and a sample removed for silylation within about 30 seconds, only one major peak was obtained, and the chromatogram was indistinguishable from that obtained by treatment of the solid anomer with the standard silylation reagent. Occasionally, minor peaks were present, preceding the peak of the a anomer these may have represented partial trimethyl-silyl derivatives (28). 

Gas-liquid chromatography was used by Coffin and DuPont (120) to separate the trimethyl silyl derivatives of the flavan-ones. Quantitation and resolution of the compounds presented some problems, and only one or two of the major flavonoids could be determined. 

Monosaccharides Monosaccharides converted to trimethyl silyl derivatives [238, 239]... 

FIGURE 13.8 Pore size distributions of (-) calcined product obtained from hexadecyltri-methylammonium-kanemite complex and (—) calcined product obtained from trimethyl-silylated derivative. (From Yanagisawa, T., Shimizu, T., Kuroda, K., and Kato, C., Bull. Chem. Soc. Jpn., 63, 1535, 1990. With permission.)... 

Gas chromatographic methods are considered to be specific for determination of hippuric acid and methylhippuric acid, although they require a derivatization procedure with various reagents for example, several investigators have used diazomethane others have used trimethyl-silyl derivatives. 

Lignin Analysis. Lignin present in fulvic and humic acids from stream, foam, and foam-extract samples from Como Creek and the Suwannee River were oxidized to phenolic oxidation products by copper oxide oxidation via the method described by Hedges and Ertel (24). These phenolic oxidation products then were derivatized to trimethyl silyl derivatives for GC/MS analysis. 

A sample of racemic 2-methylcyclohexanone-1- 3 was prepared by methylation of the lithium cyclohexanolate-l-13 , with methyl iodide (VI ) The enolate was prepared from the cyclohexanone-1-13c by way of the trimethyl silyl derivative following the pro-" cedure of House and coworkers (12). A sample of trans-D,l-2-methylcyclohexanol-l -13C was then obtained by reduction of the ketone with lithium aluminum hydride in the presence of aluminum chloride as prescribed by Eliel and coworkers (13). 

The amount of lincomycin in blood can be analyzed quantitatively by mass fragmentograph after extraction with Amberlite XAD - 2 resin followed by the formation of trimethyl silyl derivative. 

Windheuser et al. prepared the trimethyl silyl derivatives of the alkaloids by means of N,0-bis(trimethylsilyl)acetamide in an N,N-dimethylformamide solution of the alkaloids. In this way they carried out quantitative determinations of scopolamine and its acidic and basic... 

In a study on heroin metabolism Elliot et al. separated codeine, morphine, norcodeine, normorphine, 6-0-acetylmorphine, 3-0-acetylmorphine as trimethyl silyl derivatives and heroin on packed columns with SE-30 and QF-1, and assayed the amounts of morphine, 6-0-acetylmorphine and heroin in blood and urine samples, using methyl arachidate as an internal standard. 

Compound Trimethyl silyl derivatives Trifluoroacetyl derivatives... 

Hoppen et al. used a packed SE-30 column for the assay of vincamine in plasma. The molecular ion (m/e 426) and the parent peak (m/e 367) of the trimethyl silyl derivatives were assayed simultaneously by selected ion monitoring.Down to 30 pg/ml plasma could be assayed. The method is suitable for pharmacokinetic studies. Plasma samples of EDTA-anticoaaulated blood (1-2 ml) were extracted with hexane after addition of tris(hydroxymethyl)aminomethane. The aqueous phase was frozen out and the hexane phase decanted into a conical glass tube. 

Physostigmine salicylate in 0.5 % aqueous solution was determined by Teare and Borst by freeze-drying of samples of 0.2 ml, and conversion of the compound into its trimethyl silyl derivative by dissolving the residue in 5 yl of dry pyridine and 10 yl of N,0-bis(trimethyl -silyl)acetamide. The solution was allowed to stand for 1 h before injecting 1.2 yl into the gas chromatograph. A 3.8 % SE-30 on Diatoport S column and a temperature of 145°C was used for the analysis. The physostigmine THS and the salicylic acid TMS derivatives were eluted separately. Routine analysis over several days gave a precision of 11.5 %. 

A method for the gas chromatographic determination of agroclavine was developed by Barrow and Quigley10. The trifluoroacetyl derivative and the trimethyl silyl derivative were chroma-... 

The electron impact spectrum of the volatile per(trimethyl) silylated derivative of enviroxime glucuronide is shown in Figure... 

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