ISSN:0935-6304    

DOI:10.1002/jhrc.1240160902

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

年代:1993

数据来源: WILEY

摘要:

AbstractAs part of a detailed investigation into the application of GC‐FTIR in industrial and environmental analysis, representative sets of samples have been analyzed in parallel using commercial high‐sensitivity instruments. Two of the instruments utilize low temperature storage of the GC eluate to extend the time available for FTIR analysis, yielding greater sensitivity than that possible by conventional ‘light‐pipe’ GC‐FTIR. In certain circumstances, instruments using both types of sample storage give rise to spectra exhibiting features characteristic of the interface used. Chromatographic resolution was found not to be significantly degraded by use of either sample storage interface. Particular advantages were found in having parallel flame ionization detection and mass spectrometry; this enabled the location of smaller components and gave greater certainty of ide

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160903

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

年代:1993

数据来源: WILEY

摘要:

AbstractCaprolactam and oligomers can be efficiently extracted from nylon 6 by use of supercritical fluid extraction with carbon dioxide containing 7.5 % (m/m) methanol as the extraction fluid. The application of a static extraction, using an additional amount of methanol, is necessary to obtain high extraction efficiencies.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160904

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe use of cyclodextrin derivatives for the efficient separation of enantiomeric drugs is described. Hydroxypropylation, methylation or carboxymethylation of the cyclodextrin not only result in a better solubility of the cyclodextrin in aqueous solutions, but also favor,viaadditional hydrogen bonding, the stabilization of one of the cyclodextrin‐analyte complexes. The influence of the background electrolyte on peak shape is also described here. Carboxymethylated cyclodextrin can be used in similar manner to uncharged cyclodextrins at low pH values (below 4). At pH values above 5, however, its charge also allows the separation of uncharged enantiomers as in a micellar‐like sys

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160905

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

年代:1993

数据来源: WILEY

摘要:

AbstractTwo acyl and three fluoroacyl derivatives of 32 chiral alcohols have been chromatographed on a GC column coated with octakis(2,6‐di‐O‐n‐pentyl‐3‐O‐trifluoroacetyl)‐ γ‐cyclodextrin. Significant differences were observed between the stereoselectivity obtained for the derivatives and that for the underivatized alcohols. Of the derivatives, only the fluoroacylated compounds were separated into enantiomers. Derivatization with fluoroacyl groups reversed the elution order for at least some of the analytes. Stereoselectivity towards simple 2‐ and 3‐hydroxy alkanes and their fluoroacyl derivatives was highest for those alcohols with a four‐carbon chain attached to the stereogenic center. For longer‐chain fluoroacyl derivative groups stereoselectivity was higher for the 2‐ and 3‐hydroxy alkanes. Differences in stereoselectivity towards alcohols with a methyl‐branched alkane chain and their fluoroacyl derivatives was related to the distance between the methyl group and the hydroxyl or fluoroacyl groups. Different degrees of saturation in the carbon chain resulted in differences in stereoselectivity. Thermodynamic data calculated for a number of analytes suggest that the alcohols and trifluoroacetate derivatives are interacting with the stationary phase by similar mechanisms. The stereospecific interaction appears to have a hydrogen bonding or dipole–dipole contribution and some form of steric component, depending upon t

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160906

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

年代:1993

数据来源: WILEY

摘要:

AbstractTocopherol analysis in margarine is usually carried out by HPLC after saponification of the sample and extraction of the vitamin compounds; these steps consume both time and solvents. In this paper we propose an on‐line HPLC–HRGC coupling method, which allows us to simplify the preparation of the analytical sample. The sample of margarine is solubilized in hexane in an ultrasonic bath in the dark; the filtered solution is then injected into the liquid chromatograph using a normal phase microbore column eluted with hexane–isopropanol 99.8:0.2. The α‐tocopherol, which is eluted with some wax esters, is transferred on‐line to the gas chromatograph, using a loop‐type interface with the concurrent eluent evaporation and solvent vapor exit, thus it is separated from interfering compounds and determined using an Alltech RSL 300 column (22 m × 0.25 μm i.d., 0.2 μm film thickness). The β, γ, and δ–tocopherols are determined in the same LC run, using fluorimetric detection. The analysis was c

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160907

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe high selectivity of element‐specific atomic emission detection has proven suitable for screening analysis of plant foodstuffs for pesticide residues by capillary gas chromatography, especially for those foodstuffs which contain high levels of matrix compounds. The elemental composition of a peak can, furthermore, be examined by looking at the partial emission spectra recorded during a GC run. This instrumental feature prevents false positive signal interpretation as a result of high concentration levels of eluting matrix compound

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160908

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe total phenol content of soil samples has been measured using high performance liquid chromatography with electrochemical detection. Soils are extracted with sodium hydroxide solution and the phenols present in the extract are recovered on solid phase C18cartridges after pH adjustment. The measurement stage employs a short (3 cm) reversed phase column and electrochemical detection. The short column focuses the phenolic species into a single peak which can be integrated. Electrochemical detection provides both sensitivity and selectivity. Hence high speed measurement of a composite peak representing total phenol content is achieved.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160909

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

年代:1993

数据来源: WILEY

摘要:

AbstractA multidimensional gas chromatographic system has been constructed using commercially available press‐fit connectors, glass splitters, and fused silica lines. In this new design all the lines are continuously purged with carrier gas, ensuring no dead volumes in the chromatographic path. Some preliminary results and practical considerations are presente

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160910

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

年代:1993

数据来源: WILEY

摘要:

AbstractTo improve the aroma characterization of various strawberry cultivars, we tested supercritical fluid extraction (SFE) to determine its suitability for the extraction of aroma compounds from fresh fruit, comparing SFE results with traditional solvent extraction with dichloromethane. Using SFE it was possible to recover the majority of the aroma compounds which can be also found in the solvent extract; patterns related to variety and degree of maturation were preserved. Our results showed, however, that SFE is more selective and was able to recover the ‘character impact’ compound of wild strawberry. Our findings from the odor analysis of furaneol standard emphasize the importance of using a more selective extraction procedure, and always combining instrumental detection with sensory analy

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160911

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

年代:1993

数据来源: WILEY