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  • Capillary columns  (2)
  • Gas chromatography  (2)
  • Gas-solid chromatography  (2)
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  • 1
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Solid phase microextraction ; Open cap vials ; Volatile compounds (BTEX) ; Water matrix
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The testing of open cap vials in headspace solid-phase microextraction combined with capillary gas chromatography is reported. The losses of volatile analytes from such vials were analyzed theoretically and investigated experimentally. The benzene, toluene, ethylbenzene, and xylene isomers spiked in water were used as model compounds. Extraction yields and precision obtained under optimized experimental conditions as exposure time, desorption time and temperature were compared applying vials with open caps or sealed with teflon lined septa.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1612-1112
    Keywords: Gas-liquid chromatography ; Gas-solid chromatography ; Retention index data ; Cycloalkanes ; Cycloalkenes ; Cycloalkadienes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention indices of cycloalkenes and cycloalkadienes with C6–C13 rings are determined by gas-liquid chromatography (GLC) on glass capillary columns coated with OV-1 and Ucon LB 550X and by gas-solid chromatography (GSC) on a microcolumn packed with uncoated graphitized thermal carbon black (GTCB). Structure — retention correlations are derived on using index differences such as HOV, HGTCB and ΔI values, considering the differences in the stereochemistry of these compounds. It is shown that the combined application of index increments obtained in GLC and GSC provides more detailed structure informations. The value of the retention index units agree with the most stable conformations of the alicyclic compounds. The high value for the energy equivalent to an index unit (ΔGI.U.=4.18kJ/mol) confirmes that graphitized thermal carbon black causes much stronger dispersive interactions than any nonpolar liquid phase.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1612-1112
    Keywords: Gas-solid chromatography ; Graphitized thermal carbon black ; Hydrocarbon analysis ; Micropacked columns ; Separation of structural and spatial isomers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The adsorption of moelcules on the nonspecific and nonporous adsorbent graphitized thermal carbon black (GTCB) is mainly determined by their intermolecular dispersion interaction with the flat graphite surface. Since the retention values strongly depend on the geometrical configuration and shape of the investigated molecules and their arrangement on the graphite plane, it is possible to separate compounds with only small differences in their molecular shape on short columns packed with particles of pure or modified GTCB. The outstanding shape-selectivity of GTCB toward isomeric hydrocarbons is demonstrated by some examples. In most cases the elution sequences of isomeric compounds differ from that obtained in GLC using nonpolar stationary liquids. Moreover, the well defined relationship between retention data and molecular structure by adsorption on a flat and homogeneous surface give useful information for the identification of separated compounds or for the investigation of the molecular structure.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Deactivation ; Capillary columns ; Silylation ; HPLC-silica ; Surface group concentration ; Pore alterations ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High-temperature silylation (HTS) used for the deactivation of capillary columns was studied on the silica commonly used in HPLC to gain a better insight into this process. LiChrosorb Si 100 was silylated with disilazanes at different temperatures and the materials obtained were compared in terms of organic and silanol group surface concentration, IR reflection spectra, HPLC behavior, and pore distribution parameters. Applying diphenyltetramethyldisilazane, the volatile reaction products were monitored during the HTS process. With increasing silylation temperature up to 400°C the silanol surface concentration is reduced to a very small level independent of the organic group concentration which exhibits a broad maximum depending upon substituents and temperature. Up to 350°C triorganosiloxy groups prevail as bonded organic groups. It could be proved that HTS is accompanied by pore alterations of the silica matrix. Arguments proposed by different authors in explaining HTS effects are discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0935-6304
    Keywords: Gas chromatography, GC ; Capillary columns ; Deactivation ; High-temperature silylation ; Disilazanes ; Cyclosiloxanes ; Polysiloxanes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This retrospective article describes the beginnings and the development of silylation methods with diverse silazanes and siloxanes at high temperatures, and stresses their role in producing modern capillary columns characterized by a high degree of thermostability and adsorptive and catalytic inertness. Particular emphasis is placed on the outstanding contributions to this field of Kurt Grob, whose persilylation techniques provided the basis for the expansion of high resolution capillary gas chromatography.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary, glass ; High temperature silylation ; C2-C6 fatty acids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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