ISSN:0935-6304    

DOI:10.1002/jhrc.1240161102

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

年代:1993

数据来源: WILEY

摘要:

AbstractAdvantages and limitations are described for the different LC–MS interfacing systems (moving belt; direct liquid introduction; thermospray; atmospheric pressure ionization with heated pneumatic nebulizer, electrospray, or high flow ion spray; particle beam; and continuous flow fast atom bombardment). Some comments are also made about interfacing capillary zone electrophoresis (CZE).The peculiarities of the various interfaces are described, as are liquid chromatographic requirements prior to mass spectrometry using the different ionization techniques. Selected biological and environmental applications are give

ISSN:0935-6304    

DOI:10.1002/jhrc.1240161103

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

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper reports the differentiation between the enantiomers of theaspiranes and theaspirones, potent flavor compounds widely used in the flavor industry. Optically pure reference compounds of isomeric theaspiranes were obtained by enantioselective synthesis. Enantiomerically pure reference theaspirones were isolated from quince fruit; their absolute stereochemistry was assigned by CD spectroscopy. For both types of compounds the order of elution was elucidated by using authentic reference compounds. These data enabled the determination of the enantiomeric distribution of both types of compounds in a variety of plant tissues.Because of the complexity of the natural flavor isolates, compounds were identified by mass spectrometry after multidimensional gas chromatography employing a Sichromat 2 double oven chromatograph. After separation of the target compounds on the first, achiral, column (DB‐5), they were transferred to a chiral column (C‐Dex B) for determination of the enantiomeric distribution. Multiple ion detection (MID) enabled the determination of the enantiomeric distribution even for complex mixtures containing the target compounds at extremely low lev

ISSN:0935-6304    

DOI:10.1002/jhrc.1240161104

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

年代:1993

数据来源: WILEY

摘要:

AbstractIn chromatography the separation power expressed in terms of peak capacity can be greatly enhanced by multidimensional techniques. The most important aspect of multidimensional chromatography is the precise location of the heart‐cut window. Very often the reliability of this positioning is ensured by applying relatively large heart‐cuts; this reduces the intrinsic selectivity offered by the technique.The best way of locating peaks in chromatography is by means of retention indices. This technique can also be used in multidimensional chromatography. A method is described whereby the heartcut window in multidimensional gas chromatography (MDGC) can be defined precis

ISSN:0935-6304    

DOI:10.1002/jhrc.1240161105

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

年代:1993

数据来源: WILEY

摘要:

AbstractExpanded polystyrene was pyrolyzed on a laboratory scale hot wire cutter. The resulting volatiles were characterized using GC/MS as the primary analytical tool. Use was also made of retention data from a complex petrochemical standard.In situbromination of the pyrolysate further helped in structure elucidation. Air samples were collected in the field and compared to the model experiments from a laboratory scale hot wire cutter. The results indicate that alkylbenzene type compounds were the primary compounds in this environment. A few oxygenated substances were also formed. Traces of brominated compounds were detected in the model experiments but not in the samples collected in the field, with one exception. Quantitative data are presented from a typical industrial operation.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240161106

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

年代:1993

数据来源: WILEY

摘要:

AbstractCapillary GC coupled to an atomic emission detector (AED) provides a powerful new hyphenated technique for the separation and characterization of complex mixtures and compounds. The AED provides simultaneous and truly specific multi‐element detection. The specificity of detection reduces the need for the complex sample pretreatment procedures which are necessary to reduce the interference from co‐eluted substances which is experienced with detectors such as the FID and the ECD. A range of environmentally significant problems has been studied, including PCB analysis, the characterization of the reaction products of a novel waste treatment process, and the profiling of sulfur‐containing species formed by the pyrolysis of various types of

ISSN:0935-6304    

DOI:10.1002/jhrc.1240161107

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

年代:1993

数据来源: WILEY

摘要:

AbstractAn amperometric‐type electrochemical detector is proposed for use in capillary HPLC. Its cell (volume 60 nl) contains a cylindrical working electrode for detecting the presence of electroactive compounds. The noise level is 3–5 pA depending on the potential. The minimum detectable concentrations of theo‐,m‐, andp‐isomers of nitrophenol (after separation of a 20 μl sample on a fused silica column) lies between 4 and 18 ng/l. The relative standard deviation of the height of the chromatographic peaks of phenols present at concentrations of 10 ppb does not exceed 0.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240161108

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe supercritical fluid extraction (SFE) of taxicin from the dried needles of the English yew tree,Taxus baccatais described. Analysis by supercritical fluid chromatography (SFC) and proton NMR spectroscopy was used to confirm identity and purity. The extraction efficiency of SFE is comparable with that obtained using liquid solvents. Such taxanes may be used semi‐synthetically to prepare potential anti‐cancer dr

ISSN:0935-6304    

DOI:10.1002/jhrc.1240161109

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

年代:1993

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240161110

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

年代:1993

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240161111

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

年代:1993

数据来源: WILEY