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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 37 (1993), S. 179-184 
    ISSN: 1612-1112
    Keywords: Reversed-phase liquid chromatography ; Partial exclusion ; Homologous series ; Dead volume ; Linearity of ln k′
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention times or volumes in reversed-phase liquid chromatography are substantially influenced by partial steric exclusion of solutes from the pore space of the usual octadecyl silica column packings. Contrary to the common view that exclusion effects become appreciable only with “large” molecules, they are clearly observable even with solutes of a size similar to or even smaller than eluent molecules. The extent of exclusion was directly determined from elution volume versus carbon number plots of n-alkanes with n-pentane eluent. Using high precision (relative standard deviation 〈0,1%) retention data with methanol eluent, it was found that the “effective” dead volume depends on solute chain length. If such data is corrected for partial exclusion, corresponding log (capacity factors) as functions of carbon number are absolutely linear which is equivalent to perfectly constant methylene selectivity, α, within the n-alkane series. Since this observation was made on various columns with thousands of data, it may be regarded as a case of experimental proof of Martin's postulate of additivity of retention increments of molecular constituents.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1618-2650
    Keywords: Analyse von Alkylbenzolen, Alkylbromiden, Alkyldisulfiden ; Chromatographie, SÄulen ; Zusammenhang zwischen Löslichkeit u. KapazitÄtsfaktor, reverse-phase-bonded-phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Alkyldisulfide, Alkylbenzole und Alkylbromide wurden an einer chemisch gebundenen Kohlenwasserstoffphase (MicroPak-CH) mit Wasser-Methanol-Gemischen unterschiedlicher Zusammensetzung chromatographiert. In den entsprechenden Lösungsmittelgemischen wurden die SÄttigungslöslichkeiten der Probenkomponenten bestimmt. Man fand, da\ die SelektivitÄt innerhalb einer homologen Reihe durch die Löslichkeit der Glieder in der mobilen Phase bestimmt ist. Dabei lie\ sich der chromatographische KapazitÄtsfaktor mit guter Genauigkeit als k′ = b · (1/csat)2/3 darstellen. log k′ und log c sat hÄngen linear von der C-Zahl ab.
    Notes: Abstract Alkyldisulphides, alkylbenzenes and alkylbromides were chromatographed on a hydrocarbon type bonded stationary phase (MicroPak-CH) using water-methanol-mixtures of various composition as mobile phase. The solubility of the sample components was determined in the respective mobile phases. It was found that the selectivity within a homologous series is determined by the solubility in the mobile phase. The capacity factor can be expressed as k′ = b · (1/csat)2/3. Log k′ and log c sat depend linearly on the carbon number.
    Type of Medium: Electronic Resource
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