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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 29-32 
    ISSN: 0935-6304
    Keywords: Capillary electrochromatography ; electroosmotic flow ; frit ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formation of bubbles in capillary electrochromatography (CEC) is well documented: possible origins include Joule heating and variations in EOF velocity on passing from the stationary phase through the frit and into the open tube. Methods for the prevention of bubble formation are discussed which are confirmed by experimental results. Using frit lengths varying from 1 mm to 6 mm it is shown how frit length is directly related to the likelihood of bubble formation and how this is affected by applied voltage. It is shown that the change in applied voltage across a capillary affects the formation of bubbles and also that rebonding octadecylsilane (ODS) onto the silica frit after formation of the frit can minimize the formation of bubbles and how this effects the chromatography. A method is also described for increasing the robustness of silica capillaries using a column coupler along with modifications made to conventional capillary electrophoresis equipment to cater for CEC.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 7 (1995), S. 375-381 
    ISSN: 1040-7685
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Recent advances in techniques for the packing of microcolumns of down to 50 μm inner diameter using supercritical CO2 have led to rapid growth in the use of high efficiency packed capillary columns in SFC. Maximization of the usefulness and applications of these techniques requires gradient elution chromatography and the development of pumps capable of delivering 0.1 to 1 μl per minute of modifier. A micro SFC-LC pump has been tested in the isocratic and gradient elution mode with CO2 as the supercritical fluid and methanol as the modifier. The pump was tested using the EPA priority PAHs as the test mixture with a specially treated ODS column and UV detection. Results are presented for testing in the isocratic and gradient elution modes and the retention times are shown to have a coefficient of variation of less than 2%. The application of this system to the analysis of PAHs in coal derivatives is shown. The problems encountered in the use of formic acid as a modifier in SFC are discussed. © 1995 John Wiley & Sons, Inc.
    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 19 (1996), S. 527-529 
    ISSN: 0935-6304
    Keywords: High pressure gas chromatography ; Stationary phases ; Hydrocarbons ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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