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  • 1980-1984  (4)
  • Enantiomeric olefins  (2)
  • Characterization methods  (1)
  • Fluorinated ligands  (1)
  • Reversed phase HPLC  (1)
  • empirical force field
  • 1
    Electronic Resource
    Electronic Resource
    Fluorinated lignands in HPLC (1981)
    Springer
    Chromatographia 14 (1981), S. 341-344 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02259232
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Preparative LC separation and isolation of enantiomerically pure olefins (1984)
    Springer
    Chromatographia 18 (1984), S. 119-124 
    Details
    ISSN: 1612-1112
    Keywords: Enantiomeric olefins ; Platinum complexes ; Ligand exchange ; Preparative gas chromatography ; Preparative column-liquid chromatography ; Column switching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Diastereomer formation by the reaction of chiral olefins with optically active platinum complexes followed by LC separation of the diastereomers, and on-line or off-line release of the olefins from the complexes by ligand exchange yield optically pure enantiomers. The 100% dextrostetatory enantiomer of exo-2-vinylbicyclo[2.2.1]heptane (vinylnorbornane) could be isolated by an off-line method and was used for polarimetric measurements before and after preparative scale gas chromatographic clean-up. The initial valuable platinum complex could be easily recovered without loss.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02258766
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Immobilization of stationary liquids on silica particles by γ-radiation (1984)
    Springer
    Chromatographia 18 (1984), S. 265-274 
    Details
    ISSN: 1612-1112
    Keywords: New reversed stationary LG-phases ; Crosslinking of oligomers by γ-radiation ; Shielding of silanol-groups ; Surface deactivation ; Characterization methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Continuing our work on new silanization reagents for producing chemically-modified small-particle, silica support material exhibiting improved chromatographic performance and especially good shielding of silanol groups in respect of solute-stationary phase interaction, we have developed new silica-based polymer phases with different “polarities” by crosslinking or polymerization reactions induced by γ-radiation. Polybutadienes or polysiloxanes were immobilized on non-, or specially presilanized, 5μm silica particles by using different dose-rates of γ-radiation and by addition of different amounts of allylmethacrylate as a radical stabilizer. The materials obtained were tested by elemental analysis, scanning electron microscopy, ESCA and IR-reflexion measurements as well as by chemical Si−OH determinations. Chromatographic testing has been carried out with different, especially strongly basic solutes, under normal and reversed phase conditions. The dual retention mechanism model of Nahum and Horvath [1] was applied to the usual commercially available phases and those phases produced by ourselves. The influences of mobile phase additives such as acetonitrile or tetrahydrofuran were also investigated following the chromatographic test procedures for characterization of the support materials synthesized. The silicas obtained show excellent long term stability to all types of HPLC solvents. Their inertness with respect to irreversible adsorption of polar, especially basic, compounds can only be compared with that of reticular bulk polymer stationary phases without any silica skeleton. Unlike pure polymer particles these materials exhibit high pressure stability, only moderate shrinking and swelling effects, and most importantly, high plate numbers, comparable with normal brushtype stationary phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02270562
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  • 4
    Electronic Resource
    Electronic Resource
    Liquid chromatography with and of platinum complexes (1981)
    Springer
    Chromatographia 14 (1981), S. 559-566 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02262884
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    Paper (German National Licenses)
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