ISSN:0935-6304    

DOI:10.1002/jhrc.1240151002

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe capillary gas chromatographic (CGC) analysis of the der‐matological drugtrans‐acitretin (NeotigasonR) and itscismetabolite is described. Separation of the methyl ester derivatives can be achieved on a 90% biscyanopropylsiloxane phase. The importance of using cold on‐column injection and short, thin film capillary columns is discussed. For patients treated with the prodrug of acitretin, etretinate (TigasonR),i.e.the ethyl ester of Neotigason, three compounds have to be separated. Selectivity tuning is required for successful CGC separation. An alternative can be found in the selectivity of ion monitoring mass spectroscopy. Analysis of plasma samples involves liquid‐liquid extraction, a derivatization step, and HPLC purif

ISSN:0935-6304    

DOI:10.1002/jhrc.1240151003

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractNine organosulfur compounds present in an aged garlic extract and two isoflavonoids and one triterpenoid present in a licorice root extract powder have been identified and quantified. Quantification involved solvent extraction and gas chromatographic – mass spectrometric analysis (garlic extract) or hydrolysis, solvent extraction, and liquid chromatographic analysis (licorice root extract powder).Although the garlic extract proved to be unstable and the concentration of the organosulfur compounds varied with time, one analysis of the extract gave the following results: methyl disulfide (0.607 μg/g), methyl trisulfide (0.181 μg/g), allyl sulfide (2.02 μg/g), allyl disulfide (0.784 μg/g), allyl trisulfide (0.795 μg/g), allyl methyl sulfide (1.64 μg/g), allyl methyl disulfide (0.411 μg/g), allyl methyl trisulfide (0.695 μg/g), and ethyl 2‐propenesulfinate (11.4 μg/g). The analysis of the licorice root extract powder gave the following results: formononetin (1.92 mg/g), isoliquiritigenin (9.61 mg/g), and 18β‐glycyrrhetinic acid (43.9 mg/g).Methods were successfully developed to quantify the same compounds in the serum of test animals which had consumed feed spiked with garlic extract or licorice root extract powder. Only the 18β‐glycyrrhetinic acid could be detected in the sera of such animals, however. An effort was also made to determine serum levels of prostaglandin E2 to correlate its inhibition with levels of the dietary components, but the prostaglandin E2 levels were

ISSN:0935-6304    

DOI:10.1002/jhrc.1240151004

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper reports the chromatographic performance of columns coated with 2,3,6‐trimethyl‐α‐, β‐, and γ‐cyclodextrins (2,3,6‐TriMe‐α,‐ β‐, and γ‐CD) and their derivatives 2,6‐dimethyl‐3‐trifluoroacetyl‐α‐, β‐, and γ‐cyclodextrins (2,6‐DiMe‐3‐TFA‐α‐, β‐, and γ‐CD), all six diluted in polysiloxane, for the separation of the enantiomers of volatile compounds.The influence of column length and film thickness on separation is reported. Phenomena related to reproducibility and consistency, over a period of time, of columns prepared with these CD derivatives are also discussed, and a po

ISSN:0935-6304    

DOI:10.1002/jhrc.1240151005

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractIf a sample evaporates by flash vaporization in an empty injector insert, the solute material is well mixed with the expanding solvent vapors and the maximum injection volume is determined by the requirement that no vapors must leave the vaporizing chamber. If evaporation occurs from a surface (e.g., of Tenax packing), however, the solvent evaporates first. The site of evaporation is cooled to the solvent's boiling point, and the cool island formed in the hot injector retains solutes of at least intermediate boiling point (visually observed for perylene). Solvent vapors, free from such solutes, may now expand backwards from the injector insert and leave through the septum purge exit. When solvent evaporation is complete, the site of evaporation warms up, causing the high boiling solutes to evaporate and to be carried into the column by the carrier gas. The technique somewhat resembles PTV injection, but is performed using a classical vaporizing injector.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240151006

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe separation and detection of volatile organometallic compounds containing tin, iron, and nickel has been achieved using capillary GC–inductively coupled plasma–mass spectrometry (capillary GC‐ICP‐MS). Detection limits range from 3.0 to 7.0 pg/s. The presence of volatile organotin compounds in a harbor sediment has been confirmed. The retention range of the organometallic compounds analyzed by capillary GC‐ICP‐MS has been extended considerably beyond that possible in earlier studies (retention indices

ISSN:0935-6304    

DOI:10.1002/jhrc.1240151007

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractElement‐selective GC detection by microwave‐induced plasma atomic emission spectroscopy has been used to examine a wide variety of compounds containing metals, non‐metals, and metalloids. “Recipes”, or new selective detection schemes for use with the software of the computer‐controlled system, have been developed for the selective detection of boron, aluminum, gallium, titanium, vanadium, chromium, manganese, rhenium, palladium, and platinum. Figures of merit including limits of detection, linear dynamic range, and spectral selectivity over carbon have been established for most of these elements. Gas chromatography – atomic emission detection (GC‐AED) has been applied to the selective detection of vanadium, nickel, and iron in metalloporphyrins present in crude oil, manganese‐selective detection of methylcyclopentadienylmanganese tricarbonyl (MMT) in gasoline, and titanium‐selective detection of reaction mixtures containing titanium catalysts or titanium boride m

ISSN:0935-6304    

DOI:10.1002/jhrc.1240151008

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractA radio frequency plasma detector for capillary GC has been modified for oxygen‐selective detection. Purification of the plasma gas and purging of both ends of the discharge region with helium were crucial to minimizing oxygen background emission from impurities in the plasma. With a pure helium plasma, eluting hydrocarbons released oxygen from the discharge region resulting in interfering signals on the oxygen channel. These interfering signals were efficiently reduced by using a methane‐doped (0. 15%) low power RF plasma (15 W) sustained in a high make‐up flow (150 mL/min). With this plasma, a 103:1 oxygen‐to‐carbon selectivity and a 100 pg oxygen/s detection limit were obtained. The detector was linear over three orders of magnitude. The detection system has been used to screen for oxygenated compounds in two environmenta

ISSN:0935-6304    

DOI:10.1002/jhrc.1240151009

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractAn oxidation method (sulfone method) for the determination of polycyclic aromatic sulfur heterocycles (PASH) in diesel fuel is presented. The aromatic fraction of a diesel fuel, isolated by solid phase extraction, is oxidized under controlled conditions with hydrogen peroxide. The oxidation products, mainly methylated dibenzosulfone, are determined and quantified directly, without further clean‐up, by HPLC with photodiode‐array detect

ISSN:0935-6304    

DOI:10.1002/jhrc.1240151010

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractPolyvinylalcohols (PVA) and hydroxyethylcelluloses (HEC) have been used as additives in cyclodextrin‐modified capillary zone electrophoretic chiral separations of aromatic amines such as tocainide and its analogs in unpretreated 50 μm i.d. fused silica capillaries. The additives were used at low concentrations (<0.05%) in common buffers, together with the γ‐cyclodextrin as chiral selector. They reduce the electroosmotic flow,i.e.increase the migration times of the analytes in these chiral separations, and, moreover, considerably improve both peak symmetry and the widths of the peaks relative to migration time. In terms of the chromatographic theory of efficiency, more than 200000 theoretical plates can be achieved with unpretreated fused silica capillaries. This enhancement of efficiency arises because adsorptive “dynamic” coating with the hydroxylic modifier molecules suppresses adsorption of the analyte molecules by the capillary walls.The influence of field strength and buffer composition on the separation efficiency attainable with and without modifier in the buffers has also been investigated. Alternative experiments on the influence of analyte adsorption on efficiency have been performed by superimposing radial electric fields on the capillary to modify the ζ potentials. Although the EOF could be freely adjusted, it was not possible to obtain an improvement in efficiency comparable with that furnished by coating the adsorptive surface with

ISSN:0935-6304    

DOI:10.1002/jhrc.1240151011

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY