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  • 1
    ISSN: 1612-1112
    Keywords: Crosslinked phenyl silicones ; Capillary gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Methyl(phenyl)silicones offer useful selectivities when used as stationary phases in gas chromatography (GC). Such phases have, however, hitherto been of restricted importance in capillary GC due to the lack of phases having a viscosity high enough to ensure stationary phase film stability. Further, to utilize fully the possibilities of a methyl(phenyl)silicone capillary column, it must also possess high efficiency and a high degree of deactivation. In this work, the preparation of soda-glass capillary columns coated within situ cured methyl(phenyl) and methyl(tolyl)-silicones is presented. Vulcanization was made possible by the introduction of some vinyl substitution in the gum to be cured: tolyl-containing gums could be cured without the presence of vinyl groups. In addition, fused silica capillary columns coated with OV-1701 were prepared. The columns show a coating efficiency of above 80%, a thermal stability up to 320 °C and a high degree of deactivation. Their utility is demonstrated by the separation of samples containing polynuclear aromatics, antidepressants and some potent mutagens.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 506-514 
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography, SFC ; Deactivation ; Gas chromatography, GC ; Small diameter capillary columns ; Organosilicon hydrides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Small diameter fused silica capillary columns (50-75 μm i.d.) were deactivated at relatively low temperatures (250-300°C) with a mixture of polymethylhydrosiloxanes and several lowmolecular-weight organosilicon hydrides. Reproducible surface deactivations of highest quality were achieved with the polymethylhydrosiloxane (PMHS) reagent. Deactivations performed with PMHS via dynamic coating with neat or diluted reagent were evaluated by gas chromatography. Deactivations achieved with organosiloxane mono-, tri-, and tetrahydrides were also evaluated and compared. Low-molecular-weight organosilicon hydride deactivations were less time consuming and required lower head pressures for filling and coating columns with the reagent. Critical surface tensions of capillary surfaces modified with PMHS and the low-molecular-weight organosilicon hydrides gave support to the dehydrocondensation reaction between silica surface silanols and silyhydride bonds of the reagents. Slopes from Zisman plots indicated that coverage of the surface ranged from highest for the polymer (PMHS) to lowest for the monomers (TMS and PMDS). Efficiency measurements showed the influence that surface modification had on the uniformity and stability of the coated capillary columns. Well-deactivated capillary columns permitted the chromatography of polar solutes using supercritical carbon dioxide as mobile phase.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 10 (1987), S. 257-262 
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography, SFC ; Capillary columns ; Ammonia ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Instrumentation was assembled that allows the use of supercritical ammonia as mobile phase in capillary supercritical fluid chromatography. Several modifications of the typical chromatographic system were necessary, especially with respect to injection and detection. In addition, the stabilities of various polysiloxane stationary phases were studied. The chromatography of polarizable and polar basic materials was demonstrated using a nonpolar polysiloxane stationary phase.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 11 (1988), S. 75-81 
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Element selective detection ; Radio frequency plasma ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A radio frequency plasma detector for element specific detection in gas chromatography is described. The detector is comprised of a radio frequency (300 kHz) discharge between electrodes in helium, and utilizes a low-resolution emission spectrometer to monitor selected spectral emission lines produced when the helium discharge decomposes and excites the atomic constituents in the chromatographic column effluent. The spectrometer is tuned to an atomic emission line in the near-infrared portion of the spectrum, and the emission intensity from the discharge region of a selected line is used to monitor the concentration of the element producing that line. Acceptable detector sensitivity was achieved by the use of a high-throughput optical system. Selectivity was achieved by a combination of correct line selection, plasma and carrier gas purification, and plasma gas doping.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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