摘要:

AbstractMicrocolumn liquid chromatography has been interfaced with infrared microspectrometry by means of a novel technique involving electrospray nebulization. The eluent from the LC column is subjected to a high positive potential relative to the surroundings and the electric field generated charges the surface of the emerging liquid causing it to disintegrate into charged droplets which are attracted to an earthed, infrared‐transparent, zinc selenide deposition plate. Nitrogen sheath gas is used to evaporate the solvent in the droplets, and the separated components are deposited on the zinc selenide plate for subsequent analysis by means of aFouriertransform infrared microscope and spectrometer. Provided low flow rates (∼4 μl/min) are used, total elimination of the solvent is achieved and easily identifiable infrared spectra can be measured from less than 500 pg of sample (caffe

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150602

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

年代:1992

数据来源: WILEY

摘要:

AbstractNew β‐ and γ‐cyclodextrin derivatives, selectively substituted withn‐pentyl and methyl groups,e.g.heptakis(2,6‐di‐O‐methyl‐3‐O‐pentyl)‐β‐cyclodextrin, octakis(2‐O‐methyl‐3,6‐di‐O‐pentyl)‐γ‐cyclodextrin, and octakis(2,6‐di‐O‐methyl‐3‐O‐pentyl)‐γ‐cyclodextrin, have been prepared from specifically protected intermediates. The new cyclodextrin derivatives exhibit unique enantioselectivity towards important chiral constituents of essential oils. The enantiomers of lavandulol, α‐bisabolol, nerolidol, and other terpenoid alcohols could be resolved and their presence in different essential oils could be proved. Methyl jasmonate andepi‐methyl jasmonate could, in addition, be detected in jasmine concrete by two‐dimensional gas chromatography. The enantiomers of the

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150603

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

年代:1992

数据来源: WILEY

摘要:

AbstractDetermination of the rate at which volatile organic molecules diffuse through the wall of a polysiloxane rubber tube, shows that the full depth of the rubber lining of ultra‐thick film open tubular traps is utilized for the retention of volatile organic compounds in headspace gas analysis. Small apolar molecules migrate rapidly through the rubber, but larger molecules and polar compounds diffuse relatively slowly into the rubber. Neither traps with a thick film of an apolar stationary phase, nor those with an ultra thick polysiloxane rubber lining retain highly volatile compounds very effectively. Traps containing activated charcoal particles fused into their inside glass surface have a much higher capacity than those with activated charcoal particles embedded in a layer of stationary phas

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150604

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe congener‐specific analysis of polychlorinated biphenyls (PCB) by high resolution gas chromatography on a 50 m × 0.25 mm fused silica column coated with a 0.26 μm film of 5% diphenyl polydimethylsiloxane (CPSil‐8) has been significantly improved by series coupling with a 25 m × 0.22 mm column coated with a 0.10 μm film of 1,2‐dicarba‐closo‐dodecarborane polydimethylsiloxane (HT‐5). Using helium as carrier gas, a total of 64 congeners in technical PCB mixtures could be analyzed as resolved peaks by ECD (86 by MS) with the CPSil‐8 column, and 84 by ECD (108 by MS) with the combination. The high upper temperature limit for these stationary phases (>300°C) enabled fast temperature programming and rapid

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150605

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

年代:1992

数据来源: WILEY

摘要:

AbstractA porous layer open tubular (PLOT) column has been used for monitoring the light hydrocarbons and permanent gases produced in coking plants. The method, which offers a simple alternative to traditional multi column techniques, entails a single injection on to a Carboplot 007 capillary column and simultaneous thermal conductivity and flame ionization detection. The simplified approach proposed is restricted to coke oven gas analysis: application to other gas mixtures has not been considered.The reliability of this procedure compares favorably with that of traditional methods; the technique is also much less time‐consuming: seven individual gases can be determined on‐line every fifteen minutes. Primary and secondary gas standards were used to determine response curves for the gases.The method also facilitates reliable calculation of heat values associated with the burning of the fuel gas mixtu

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150606

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

年代:1992

数据来源: WILEY

摘要:

AbstractA system is presented which combines multidimensional GC with isotope ratio mass spectrometry. The performance of the system is demonstrated with an application from the field of flavor analysis. Potentials and limitations of the technique are also discussed.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150607

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe separation of new, artificial, non‐sulfated glucosinolates and desulfated natural glucosinolates on different apolar (C8, TMS, phenyl) or weakly polar (CN) bonded stationary phases by gradient elution has shown that apolar or weakly polar bonded silica‐based adsorbents, in addition to the C8 phase chosen for the standard procedure, can be used with benefit for the analysis of glucosinolate mixtures.The use of new artificial glucosinolates, not present incruciferae, as internal standards for the standard HPLC method for the determination of the main glucosinolate composition and content of rapeseed is discussed.The main factors influencing the retention and selectivity toward several natural and artificial non‐sulfated glucosinolates for different chromatographic systems have been studied, and for additional information the retention data have been analyzed statistically by factor analysis.The first results from this study show that the mechanism of the HPLC retention of glucosinolates is the sum of only two methematically independent physico‐chemical phenomena. The first is associated with the hydrophobicity of compounds.A better understanding of the chromatographic behavior of glucosinolates has made it possible to investigate the synthesis of new, artificial standard glucosinolates with the intention of providing an ideal standard for every kind of analysis. It also supplies a tool to enable laboratories to choose the best chromatographic system for a particular selectivity

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150608

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

年代:1992

数据来源: WILEY

摘要:

AbstractAs most sample liquids tend to pass through an empty injector insert at a speed which is too high to enable complete evaporation, movement of the liquid must be arrested before it reaches the column entrance. Stopping the liquid means deposition on to a surface; this, however, is possible only after the temperature of the surface has been cooled to (or below) the boiling point of the liquid (solvent).The performance of different means of stopping the liquid has been tested visually (by the method described in Part 2). Baffles on the wall of the injector insert had hardly any effect on evaporation: the band of liquid leaving the syringe needle performed a perfect slalorn around them. The inverted cup proved more efficient, but the best performance was obtained from a light plug of glass wool: owing to its low thermal mass, the first fibers to be met by the liquid are immediately cooled to the solvent boiling point, allowing the liquid to wet it. The sample liquid is sucked up by the glass wool, from where the sample evaporates relatively slowly, often over a period of several seconds.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150609

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

年代:1992

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150610

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

年代:1992

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150611

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

年代:1992

数据来源: WILEY