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  • Analytical Chemistry and Spectroscopy  (3)
Document type
Keywords
Publisher
Years
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 341-343 
    ISSN: 0935-6304
    Keywords: Capillary SFC ; Column coupling ; Restrictor ; Dead volume ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 4 (1992), S. 215-220 
    ISSN: 1040-7685
    Keywords: retention index ; supercritical fluid chromatography ; selectivity ; temperature ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Retention indices (RI) for a variety of probe compounds were determined on 50-μm i. d. columns coated with eight different stationary phases under density programmed SFC conditions at isothermal temperatures of 80 and 150°C. RI values were strongly dependent on temperature for polar probes on the polar phases containing high levels of cyanopropyl or polyethylene glycol (PEG) functionality. A lower apparent polarity was observed for polar columns at higher temperatures. Moderate RI differences were apparent with the same probes on columns with polarizable stationary phases of high phenyl or biphenyl content. Nonpolar alkyl substituted stationary phases showed only a slight temperature dependence on RI for all test compounds. Alkanes of lower molecular weight eluted at lower densities on all columns when the temperature was raised because of the contribution of volatility to elution in SFC. This same effect was observed for the higher alkanes on both nonpolar and PEG columns, but they eluted at similar densities on cyanopropyl columns and at higher densities on columns with polarizable phases when the temperature was raised. Temperature controlled selectivity tuning is a useful tool in optimizing separations in SFC.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 4 (1992), S. 221-225 
    ISSN: 1040-7685
    Keywords: Azo-t-butane ; cross-linking ; immobilization ; capillary columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ability of commercially available azo-t-butun (ATB) to facilitate immobilization of polysiloxane stationary phases in capillary columns deteriorates upon storage. Aged ATB produces columns with high bleed, solute retention shifts, erratic immobilization efficiency, and high activity. This deterioration is accelerated in the presence of light, suggesting free radical processes are involved. The loss of certain lowlevel impurities, which act as free radical transfer agents or radical sinks, may be responsible for the performance change. Regeneration can often temporarily be accomplished using platinum catalyzed reduction with trichlorosilane. The addition of small amounts of toluene or other radical transfer agents to aged ATB moderates the cross-linking process, allowing the reproducible production of columns with good immobilization efficiency, excellent intertness, low thermal bleed, and proper polarity.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
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