摘要:

The separation and characterization of pregnenolone, its 3-sulfate and dehydroepiandrosterone in rat brains (neurosteroids) were carried out using liquid chromatography/mass spectrometry. The genins obtained from rat brains were acetylated and then derivatized withO-methylhydroxylamine to give the respective acetate-methyloximes, which were identified by comparison of their chromatographic behavior with authentic samples during liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry. Pregnenolone 3-sulfate in rat brains was also identified with an authentic sample using liquid chromatography/electrospray ionization-mass spectrometry.

ISSN:1082-6076    

DOI:10.1080/10826079808000507

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This work reports the direct separation of twenty one Fmoc, Boc, Trt, and Pmc, single and double protected amino acids (PAA) using protein-based and macrocyclic antibiotic-based chiral columns. This group of PAAs represents a cross-section of commonly employed reagents in peptide synthesis with diverse structures and protecting groups. The Ultron Ovomucoid (OVM) chiral column was found to be extremely versatile in the resolution of these molecules without the need of any chemical modification. Compounds not separated in the Ovomucoid column, were resolved using Human serum albumin (HSA) and Chirobiotic T (Teicoplanin) columns.

ISSN:1082-6076    

DOI:10.1080/10826079808000508

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A procedure for sample clean-up, isolation of glycoconjugates, and analysis of the two major sialic acids, Neu5Ac and Neu5Gc, as per-O-benzoylated derivatives in biologic samples is described. In blood sera, the bulk of low molecular weight molecules was efficiently removed by precipitation of sialic acids containing glycoconjugates with saturated ammonium sulphate, pH 10, at 0°C, centrifugation, and gel chromatography on a Sephadex G-25. The tissue specimen was homogenized with water at 0°C and following centrifugation the water-soluble sialic acids containing glycoconjugates were recovered in the supernatant. Sialic acids were liberated from their isolated macromolecules by acidic hydrolysis with 25 mM trifluoroacetic acid at 80°C for 2 h. Constituents with positive charged groups and neutral monosaccharides were removed by ion-exchange chromatographies on Dowex 50X8 and Dowex 1X8, whereas sialic acids were eluted with 2M formic acid.

ISSN:1082-6076    

DOI:10.1080/10826079808000509

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A gradient RP-HPLC bioanalytical method has been developed for the human pharmacokinetic studies of girisopam, the new 2,3-benzodiazepine compound with anxiolytic effect that has no myorelaxant and anticonvulsive side effects. The compound is an analogue of tofizopam (Grandaxin®, EGIS Pharmaceuticals Ltd., Budapest, Hungary). The method was found to be appropriate for the purposes of human pharmacokinetic studies performed at 25, 50, 100, 200, 325, and 525 mg dose levels. The method allowed the simultaneous determination of girisopam (G) and its four metabolites (4′-hydroxy-G, 7-demethyl-G, 4-hydroxymethyl-G and 4-demethyl-4-oxo-G) identified in previous studies in human plasma. The solutes were separated on Hypersil BDS C18 column and quantified by UV detection at 238 nm. A solid phase extraction (SPE) method using reversed-phase cartridges was developed for sample processing, whereby girisopam and the much more polar metabolites, as well as the internal standard could be extracted in a single step.

ISSN:1082-6076    

DOI:10.1080/10826079808000510

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Azithromycin has become one of the most widely prescribed macrolide antibiotics due to the pharmacokinetic profile and broad spectrum of activity. A method for determining the level of azithromycin in ferret feces involving drying, methylene chloride extraction, solid phase extraction (SPE) clean-up, and HPLC analysis was developed. The method was linear from 0.8 to 3.2 mg/mL with a mean recovery of 97% (0.6% RSD for 50 mg spiked simulated feces). The analysis was developed to quantitate approximately 50 mg of azithromycin in approximately 0.6g of dried feces.

ISSN:1082-6076    

DOI:10.1080/10826079808000511

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A liquid-chromatographic procedure is proposed for the simultaneous determination of benzoic and sorbic acids in fruit-derived products. Prior to the chromatographic separation, a clean-up pre-treatment of the sample is carried out off-line, using successively an anionic resin and a C18stationary phase as sorbent beds. After elution from the cartridges, the acids are separated and quantitated by LC with UV-absorbance detection. The validation tests show that the technique can be applied to different types of fruit-derived products (i.e. jams, dried fruits and almond paste).

ISSN:1082-6076    

DOI:10.1080/10826079808000512

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Iron has been determined in commercial and high purity copper cables using high performance ion-pair liquid chromatography (IPC). The proposed method avoids pre separation/preconcentration of trace impurities from bulk copper saving considerable sample preparation time. Tetrabutyl ammonium ion (TBA)+was mainly used as an ion pairing reagent. The UV detector response for iron and copper at various wavelengths has been optimized. The accuracy of the developed method is tested by comparing its results with inductively coupled plasma atomic emission spectrometry for the assay of iron in spiked solutions, standard reference material (SRM), and in locally available copper based electrical cables. The relative standard deviation for sample 7 (n = 5) is 1.23%.

ISSN:1082-6076    

DOI:10.1080/10826079808000513

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A straightforward and reliable HPLC method is described, allowing the trace determination of 16 fluorinated aromatic carboxylic acids in aqueous reservoir fluids. Thirteen of these tracer compounds can be determined simultaneously. Concentrations as low as 10 μg/L were determined for selected acids in aqueous reservoir fluids, without sample preparation. The reversed phase column retarded the natural organic background present in aqueous reservoir samples until the selected tracer compounds had been eluted from the column. The use of a diode array detector enabled the identification of the fluorinated benzoic acids. The described technique was used for the reliable determination of the water tracers 2,6-difluorobenzoic acid, 2-fluorobenzoic acid and 3-fluorobenzoic acid in aqueous reservoir samples from a North Sea reservoir.

ISSN:1082-6076    

DOI:10.1080/10826079808000514

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

An HPLC procedure for determining phenylurea herbicides in waters is described. A LichroSpher RP select B octadecyl-silane analytical column and spectrophotometric detection at 247 nm were used. Adequate retention was achieved with a mobile phase containing ACN/H2O 35/55 (v/v) and 10−2M phosphate (pH = 7). The herbicides were isolated from water samples by using a single solid phase extraction procedure with C18solid-phase columns. An enrichment factor of 333 is achieved. The coefficients of variation of the method were lower than 8% at 3 μg L−1herbicides concentration level. Recoveries ranged between 93 and 105%. The results obtained indicate that the proposed method is well suitable for monitoring phenylureas in compliance with the European Community standard for drinking water.

ISSN:1082-6076    

DOI:10.1080/10826079808000515

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Among the different methods of changing the color of human hair, oxidative hair dyeing plays an important role. The formulations consist of a broad spectrum of organic compounds among which most of the dye forming substances, i. e. the dye intermediates, are of aromatic nature. With the aim of establishing an analytical method for the separation and quantification of the dye intermediates, the chromatographic behavior of a selection of these products was investigated. The separation was done by HPLC, using reversed-phase chromatography. UV and diode array detection were employed. A quantitative separation procedure was established with which it is possible to separate and identify intermediates according to their retention times and their UV spectra.

ISSN:1082-6076    

DOI:10.1080/10826079808000516

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor