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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 14 (1981), S. 341-344 
    ISSN: 1612-1112
    Keywords: Reversed phase ; Fluorinated ligands ; HPLC ; Solubility theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chromatographic behaviour of C6F5(CH2)3SiCl3, C6H5(CH2)3SiCl3, CF3(CF2)7CH2CH2SiCl3 and n-C10H21SiCl3 as well as the bonding of these ligands to silica is described. Phases with partially fluorinated ligands show entirely different chromatographic characteristics to analogous phases, where hydrogen replaces fluorine. The silica with the pentafluorophenyl-3-n-propyl-C6F5(CH2)3-ligand has higher k′-values and a better selectivity for aromatic hydrocarbons than that with phenyl-3-n-propyl C6H5(CH2)3-groups, whereas the phase with the fluorinated carbon chain is less useful than the silica modified with n-decyltrichlorosilane n-C10H21SiCl3. The first effect can be explained by complex formation, and the second may be due to a different contact area between the ligand and the solute. The normal hydrocarbon chains hinder each other sterically and expose many adsorption sites, in contrast the perfluorinated chains are sterically fixed and are the first example of “real brushes” in HPLC.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 14 (1981), S. 559-566 
    ISSN: 1612-1112
    Keywords: Reversed phase HPLC ; Normal phase HPLC ; Platinum complexes in mobile phase ; Enantiomeric olefins ; Diasteromeric complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Reversed-phase, high-performance liquid chromatography (HPLC) on chemically bonded C18-phases with acetonitrile-water mobile phases, contianing platinum complexes like Zeise's salt C2H4PtCl3, the amine derivative C2H4−PtCl2−NH2−CH(CH3)−C6H5 or the amino acid compound C2H4−PtCl−OOC−CH(N(CH3)2)−C6H5 by analogy with argentation chromatography, was used to increase selectivity for the separation of various types of olefins, amines and heterocyclic compounds. On the other hand, normal-phase adsorption chromatography on silica with n-heptane, dichloromethane and n-propanol mobile phases proves to be an ideal tool for the analytical and preparative separation of diastereomeric platinum complexes of olefins, introduced by Gil-Av, that can be easily preparedin vitro, by the reaction of C2H4−PtCl−OOC−CH(N(CH3)2)−C6H5 with optically active olefins in CH2Cl2. The preparation of the intitial complex as well as its application to the separation of several interesting types of enantiomeric olefins is described and discussed. The number and amount of separable diastereomers formed by the above reaction is strongly influenced by sterical effects. By comparison of the chromatographic pattern of either racemic or partly racemic mixtures, it is possible to decide, which peaks belong to one or the other enantiomeric form of the olefin.
    Type of Medium: Electronic Resource
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