摘要:

AbstractMicellar electrokinetic capillary chromatography has been explored as an efficient and rapid method of separating the photoproducts of 2′‐deoxyuridylyl‐(3′‐5′)‐thymidine (i.e.,cis‐synandtrans‐syncyclobutane dimers, (6–4) photoproduct, and the relatedDewarvalence isomer) from normal nucleosides and nucleotides. Three cationic surfactants, dodecyl‐, tetradecyl‐, and hexadecyltrimethy‐lammonium bromide were evaluated and the separations compared with those obtainable with the anionic surfactant, sodium dodecylsulfate. Optimum resolution of the dinucleoside monophosphate photoproducts was obtained using tetradecyltrimethylammonium bromide. By use of this detergent the photoproducts could also be separated from other normal constituents in less than 6 min at −25 kV. Dodecyl‐ and hexadecyltrimethylammonium bromide provided some separation between the various species but sodium dodecylsulfate did not separate the UV radiation‐induced products from either the parent compound or other dinucleoside monophosphates. Increased interaction between negatively charged solutes and positively charged micell

ISSN:0935-6304    

DOI:10.1002/jhrc.1240170102

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

年代:1994

数据来源: WILEY

摘要:

AbstractTrifluoroethyl ester‐functionalized polysiloxanes can be prepared by block condensation of 3‐dichloromethylsilyl‐2‐methylpropionic acid 2′,2′,2′‐trifluoroethyl ester with 1,5‐bis(diethylamino)hexamethyltrisiloxane or with disodium tetramethyldisiloxane‐1,3‐diolate. The functionalized polysiloxanes may serve as supports for a variety of selector groups; for instance, nucleophilic displacements with L‐valine‐t‐butylamide or L‐α‐naphthylethylamine lead to chiral polysiloxanes in high yields and with high reproducibility. Imidazole accelerates the rate of nucleophilic displacement. Capillary columns coated with such chiral polysiloxanes exhibit high enanti

ISSN:0935-6304    

DOI:10.1002/jhrc.1240170103

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

年代:1994

数据来源: WILEY

摘要:

AbstractSorbitan ester surfactants are very complicated mixtures. An improved and simple reversed phase high performance liquid chroma tographic (HPLC) method employing a C18column has been developed for the rapid separation of sorbitan ester surfactants and the quantitative determination of the distribution of sorbitan mono‐, di‐, tri‐, and tetraester fractions. The sorbitan ester distribution of the six Span and Arlacel surfactants studied was calculated using relative response factors obtained from analysis of pure glycerides of fatty acids. The effects of mobile phase composition on the accuracy and reliability of the distribution values calculated for the sorbitan esters were investi

ISSN:0935-6304    

DOI:10.1002/jhrc.1240170104

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

年代:1994

数据来源: WILEY

摘要:

AbstractThermochemical conversion of biomass produces solid charcoal, gaseous fuels, and condensable oils. Because these oils vary widely in composition depending on the cellulosic feedstock and the operating conditions used, analysis of the oils is necessary in order to determine the best ways of utilizing or disposing of them. The major components of the organic oil from pyrolysis of gorse have been characterized by capillary gas chromatography – mass spectrometry. A qualitative study of the aqueous oil from the same source has also been attempte

ISSN:0935-6304    

DOI:10.1002/jhrc.1240170105

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

年代:1994

数据来源: WILEY

摘要:

AbstractThree different types of SCD combustion source have been evaluated for use in the chromatographic analysis of atmospheric sulfur compounds. The conventional FID source and the newer inverted burner source were found to be less sensitive and less stable than the flameless design. Overall, the flameless source was superior for use with HRGC‐SC

ISSN:0935-6304    

DOI:10.1002/jhrc.1240170106

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe aim of this study was to test the suitability and performance of various stationary phases and column dimensions for dynamic headspace gas chromatography of food aromas. The trials were performed using an aqueous test mixture containing thirty seven volatile flavor components of intense aroma, and a sample of ripe Swiss Emmental cheese.The best performance with both samples was obtained with a capillary column coated with a thick film of polydimethylsiloxane. This column resolved the greatest number of compounds in the cheese sample and resulted in the overlapping of one pair of peaks only from the test mixture. Because of its other advantages,i. e.high capacity owing to its film thickness, and insensitivity to the high moisture content of some samples or traces of oxygen in the carrier gas, the polydimethylsiloxane column appears suitable for the analysis of the volatile and highly polar compounds present in complex mixtures such as food aroma.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240170107

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe polarity of carbon layer open tubular (CLOT) columns coated with a layer of non‐porous graphitized carbon black (Carbopack B) modified with an appropriate amount of polar polyglycol liquid phase has been evaluated and compared with that of standard polar (Supelcowax‐10) and non‐polar (SPB‐1) bonded phase open tubular columns. The efficiency and selectivity were measured at various temperatures and the polarity of the columns was evaluated by use ofMcReynolds' constants and the difference in apparent carbon number, ΔCof linear alkanes and alcohols. The polarity of the CLOT column was found to depend on temperature, and changing the analytical conditions therefore enabled the separation of compounds of different polarity whose reciprocal position and resolution were affected by temperature. The application of calculation methods which enable programmed temperature retention times to be predicted from isothermal data was also found to be possible when the polarity of the CLOT column changes with tem

ISSN:0935-6304    

DOI:10.1002/jhrc.1240170108

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

年代:1994

数据来源: WILEY

摘要:

AbstractDeactivation of precolumns with an ultra thin film of OV‐1701 provided inertness at least equal to silylation, but better resistance to water. Dynamic coating of the raw fused silica capillary is, furthermore, much faster than the hydrothermal treatment/silylation procedur

ISSN:0935-6304    

DOI:10.1002/jhrc.1240170109

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

年代:1994

数据来源: WILEY

摘要:

AbstractFast and efficient separations of chiral stereolabile compounds were obtained at very low temperature on a π‐acid chiral stationary phase (R,R‐DACH‐DNB) using carbon dioxide‐based mobile phases containing alcoholic polar modifiers.Furthermore, efficient separations of the newly discovered spherical carbon cluster buckminsterfullerene (C60) and the related higher fullerenes (C70,etc.) have been performed on the same stationary phase using eluents based on eithern‐hexane or carb

ISSN:0935-6304    

DOI:10.1002/jhrc.1240170110

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

年代:1994

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240170112

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

年代:1994

数据来源: WILEY