A procedure for the measurement of pregnanetriol in urine by gas chromatography is described. The internal standard is added to the standards, controls and unknowns prior to the enzymatic hydrolysis of the steroid conjugates. Next, the hydrolyzed steroids are extracted from urine and converted to the volatile trimethylsilyl ether derivatives prior to gas chromatography. The initial addition of ...

Twenty-seven strains belonging to 12 Mycobacterium species were studied for 3-hydroxy fatty acid composition. Mycobacterial cells were subjected to both mild and strong acid methanolysis, after which the liberated hydroxy fatty acids were purified and analyzed by gas chromatography-mass spectrometry as methyl ester trimethylsilyl ether derivatives. Altogether, 21 3-hydroxy fatty acids containin...

Trimethylsilylation of alcohols and phenols were carried out under solvent-free conditions with hexamethyldisilazane (HMDS) using LaCoO3 perovskite. LaCoO3 as an efficient catalyst accelerated this reaction under milder condition. The advantages of this method are evident regarding, easy separation, low cost and low catalyst loading, lack of pollution, easy work-up, and selective protection of ...

A rapid and easy-to-perform method for the screening and confirmation of estrogens, gestagens and androgens (EGAs) in kidney fat has been developed. In this investigation only 5 g of fat was needed. After extraction with acetonitrile the steroid phase was defatted using n-hexane. Followed by a saponification step, the sample extract was purified by solid phase extraction. After derivatisation a...

A simple method for the gas-liquid chromatographic quantitation of human fecal bile acids and sterols is described where bile acids are subjected to n-butyl ester derivatization, without prior isolation from the stool, followed by trimethylsilylation of the sterols and bile acids. Under these conditions, bile acid derivatives are well resolved from each other and from the trimethylsilyl ether d...

The asymmetric tandem oxa-Michael-aldol reaction of salicylic aldehyde derivatives with alpha,beta-unsaturated aldehydes catalyzed by a chiral amine/chiral acid organocatalytic system was investigated. The organocatalytic system of (S)-diphenylpyrrolinol trimethylsilyl ether with chiral shift reagent (S)-Mosher acid presented a synergistic effect in the improvement of reaction performance and o...

Phenylalanine in serum and urine was determined by gas chromatography after it was converted, by action of nitrous acid, to the corresponding hydroxy acid, phenyllactic acid. After extraction with ether, the phenyllactic acid was derivatized with bis(trimethylsilyl) trifluoroacetamide under mild conditions, and the product was injected directly into the gas chromatograph. The precision of the m...

Novel unsaturated ethers were synthesised in good yields starting from sucrose,using a two-step mild and efficient procedure based on the Gassman method, which consists in forming a vinyl group by the elimination of ethanol from mixed acetals with trimethylsilyl trifluoromethanesulfonate in the presence of alkyl amines. Mixed acetals are readily obtained from the corresponding alcohols and ethy...