A gas-liquid chromatographic method for steric analysis of epoxy acids

A gas-liquid chromatographic method for determination of the absolute configuration of the two chiral carbon atoms of epoxy fatty acids was developed. The method involved (1) conversion of the saturated epoxy ester into a pair of regioisomeric allylic alcohols by consecutive treatments with selenophenoxide anion and hydrogen peroxide, (2) oxidative ozonolysis performed on the (-)-menthoxycarbonyl derivatives of the allylic alcohols, and (3) steric analysis of the resulting two 2-hydroxy acids (methyl esters, (-)-menthoxycarbonyl derivatives) by gas-liquid chromatography using appropriate reference compounds. Application of the method for steric analysis of several synthetic epoxyoctadecanoates as well as (+)-vernolic acid derived from Vernonia galamensis is described.     

A thin-layer chromatographic method for the quantitative separation and estimation of S-adenosylmethionine and S-adenosylethionine in rat liver

A procedure is described for the simultaneous isolation, separation, and quantitation of S-adenosylmethionine (AdoMet) and S-adenosylethionine (AdoEt) in rat liver. These compounds are isolated by precipitation with ammonium reineckate, are separated by thin-layer chromatography, and are quantitated by an isotope dilution determination. The procedure was tested with commercial standards added to liver homogenate ranging up to 160 μg AdoMet/g liver and 173 μg AdoEt/g liver; at all of the concentrations tested, the recoveries were linear and accurate. AdoMet recoveries were linear in the presence of 11.6 or 307 μg AdoEt/g liver, and AdoEt recoveries were linear in the presence of 37.8 or 191 μg AdoMet/g liver. AdoMet and AdoEt levels were measured in the livers of rats fed diet containing 0 or 0.3% dl-ethionine for 2 weeks. In the ethionine-treated animals, AdoMet concentrations were lower than in the controls; and, conversely, AdoEt increased from 0 to 259 μg/g liver.     

A rapid gas-liquid chromatographic method for the quantitation of urinary estrone, estradiol-17 , estriol, and pregnanediol throughout pregnancy

A rapid, sensitive and inexpensive method is presented for the determination of urinary estrone (E₁), estradiol-17β (E₂), estriol (E₃), and pregnanediol (P₂) in pregnancy urine. The assay involves enzymatic hydrolysis, ion-exchange chromstography, and final quantitation of the steroids as heptafluorobutyric anhydride derivatives in a gas Chromatograph. Twenty to 30 samples may be prepared for gas-liquid chromatography in one working day. For six samples, the results including gas-liquid chromatography and calculation can be obtained eight hours after receiving the urine specimens thus competing in speed with radioimmunoassays. The method is sensitive enough to allow urines from less than six weeks after the last menstrual period to be quantitated.     

An improved gas-liquid chromatographic method for the determination of fecal neutral sterols

The analysis of fecal neutral sterols has been improved by use of a highly selective gas-liquid chromatography column packed with SP-2401. This chromatographic column allows separation of cholesterol and cholestanol and delta 5-5 alpha plant sterol homologs without employing silver nitrate thin-layer chromatography. Furthermore, there is no need to derivatize neutral sterols before injection. The main fecal neutral sterols are well resolved; retention times are reproducible; detector response is reproducible, linear, and sensitive to 0.2 micrograms. This method, successfully used for fecal samples, may be suggested as a routine method for the clinical study of cholesterol metabolism.     

A simple and sensitive method for the quantitative estimation of collagen.

A method to quantitate collagen in solution is described. It is based on binding of the dye Sirius Supra red F3BA by collagen followed by elution and estimation of the bound dye in a spectrophotometer. The assay can be used in the range from 10 to 100 μg protein. The method is rapid, specific, simple, sensitive, and highly reproducible.     

New electron-capture gas-liquid chromatographic method for the determination of mexiletine plasma levels in man

A method for the determination of mexiletine in human plasma by gas—liquid chromatography with electron-capture detection is described. Plasma samples are extracted at pH 12 with dichloromethane after addition of the internal standard, the 2,4-methyl analogue of mexiletine. A derivative is obtained using heptafluorobutyric anhydride; according to gas chromatography—mass spectrometry it is a monoheptafluorobutyryl compound. The minimum detectable amount of mexiletine is 5 pg. Accurate determinations of human plasma levels were performed after oral or intravenous treatment.     

A modified method for the estimation of pregnanediol, pregnanetriol and seven common 17-ketosteroids in urine by gas-liquid chromatography

A method is described for simultaneous determination of seven common urinary 17-ketosteroids, pregnanediol (5β-pregnane- 3α, 20α-diol) and pregnanetriol (5β-pregnane-3α,17α,20α-triol) by gas-liquid chromatography. The essential steps include hydrolysis of conjugates by an extract from $\text{Helix}$$\text{pomatia}$, use of 5β-cholestan-3α-ol as an internal standard, silylation and gas chromatography using 3% XE-60 as a stationary phase. The chromatograms were clear and the peaks easily identifiable. Laborious purification procedures were not necessary. 5β-pregnane-3α,20α-diol and 5β-pregnane-3α, 17α,20α-triol were measured in 22 adult males and 17 adult females. The subjects were trained hospital personnel, healthy and without medications. The results, in general, were in agreement with those reported by others.     

A new method for quantitative estimation of the virus particles number

The virus particles of live mumps virus vaccine widely used for vaccination in Russia have been detected and visualized by the atomic force microscopy. For quantitative estimation of the number of observed virus particles the special method has been developed. The presence of the vaccine virus protein component was tested by ELISA and dot-blot analysis. Using a quantitative real-time PCR assay the number of copies of viral RNA was estimated. The results of the quantitative estimation obtained by real-time PCR corresponded to the atomic force microscopy data.     

A gas chromatographic method for the quantitative detemination of hexuronic acids in alginic acid

A method has been developed for the quantitative determination of the relative proportions of d-mannuronic and l-guluronic acids in alginic acid. To obtain homogeneous reaction conditions the viscosity of the alginic acid sample was first decreased by limited hydrolysis with mineral acid. The carboxyl groups were then esterified by reaction with 1-ethyl-3-[3-(dimethylamino)propyl]-carbodiimide, and reduced with sodium borohydride. The resulting hexosans were converted by acid hydrolysis to d-mannose and an equilibrium mixture of l-gulose and 1,6-anhydro-l-gulose. These were treated with sodium borohydride; the 1,6-anhydro-l-gulose was not reduced whereas d-mannose and l-gulose were converted to d-mannitol and d-glucitol. The hexitols were estimated by gas-liquid chromatography as the n-butane boronic acid esters, and the relative proportions of the uronic acids in the alginic acid were calculated by taking into account the equilibrium ratio of l-gulose and 1,6-anhydro-l-gulose. The method can be used to analyze as little as 2 mg of alginic acid.     

A sensitive and specific method for quantitative estimation of carbamylation in proteins

A simple, rapid, reproducible, and specific micromethod for the estimation of carbamylation of proteins is described. The method is based on permanganate oxidation of radioactive carbamyl derivatives of protein to form urea and on the specific decomposition of urea by urease.