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  • 1
    Digitale Medien
    Digitale Medien
    Spectroscopic studies of butylphenyl, mono-ol and perfluorinated bonded phases (1994)
    Springer
    Chromatographia 39 (1994), S. 520-528 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; New bonded phases ; 13C and29Si CP-MAS NMR ; DRIFT ; ESCA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A variety of olefins were bonded to silaceous supports through a hydride modified substrate. The products were then examined by13C and29Si solid state-NMR with cross-polarization (CP) and magic angle spinning (MAS). Information about the surface was also obtained by diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) and the related photoelectron spectroscopic technique (ESCA). Carbon analysis on bonded silicas was carried out and surface coverage was calculated. Confirmation of the organic groups bound to the silica support was possible. The hydride intermediate is shown to be a versatile material for bonding a wide variety of organic moieties to silica surfaces.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02268274
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  • 2
    Digitale Medien
    Digitale Medien
    Retention of fullerenes by octadecyl silica. Correlation with NMR spectra at low temperatures (1995)
    Springer
    Chromatographia 40 (1995), S. 507-512 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Fullerenes ; Retention vs NMR spectra ; C18 phases ; Low temperature separations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The temperature effect on the retention of fullerenes in the range 80°C to −70°C in liquid chromatography (LC) has been examined using octadecylsilica stationary phases (ODS). It has been found that the maximum retention temperature lies around −10°C with a highly carbon loaded ODS phase. Solid state CPMAS NMR measurements on the stationary phases indicated that the relaxation time at the 30 ppm methylene signal changes with the temperature and has a minimum relaxation time at the temperature which closely matches the maximum retention temperature observed in chromatography. The interpretation of both NMR spectroscopic and LC chromatographic data are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290260
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  • 3
    Digitale Medien
    Digitale Medien
    Synthesis and characterization of titania based stationary phases using the silanization/hydrosilation method (1997)
    Springer
    Chromatographia 44 (1997), S. 538-544 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Octadecyl titania ; Hydride surface ; Hydrosilation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The silanization/hydrosilation bonding method is tested on both a laboratory synthesized and commercial titania. The laboratory titania made by the sol-gel process shows evidence of residual organic material that is removed by an initial acid hydolysis followed by bonding of the hydride (triethoxysilane) under acidic conditions. DRIFT and solid state CP-MAS NMR studies are used to confirm the formation of the hydride layer on the titania and the success of the hydrosilation process for attaching an organic moiety (1-octadecene) to the surface. Chromatographic testing, primarily on the commercial titania based C-18 phase, indicates good reverse phase properties and few residual OH groups, either Ti−OH or Si−OH, as determined by the symmetrical peak shapes obtained for anilines and alkylphenylamines using mobile phases with no buffers or masking agents in the aqueous component.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02466748
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  • 4
    Digitale Medien
    Digitale Medien
    Effect of temperature on the mechanism of retention of fullerenes in liquid chromatography using various alkyl bonded stationary phases (1996)
    Springer
    Chromatographia 42 (1996), S. 56-62 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Fullerences ; Alkyl bonded silica phases ; Retention vs. column temperature ; CP-MAS NMR
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The temperature-dependency of the separation of fullerenes in liquid chromatography (LC) has been examined using various alkyl bonded stationary phases. It has been found that a maximum retention temperature exists with long alkyl bonded stationary phases, whereas there is no similar effect with the newly synthesized alkyl bonded phases which have two phenyl groups at the base of the bonded phase. The interpretation of the retention behavior of fullerenes in the low temperature region on alkyl bonded stationary phases is discussed using information obtained by CP-MAS solid-state NMR spectroscopy and LC.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02271056
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  • 5
    Digitale Medien
    Digitale Medien
    HPLC evaluation of mono-ol, butylphenyl and perfluorinated columns prepared via olefin hydrosilation on a silica hydride intermediate (1996)
    Springer
    Chromatographia 43 (1996), S. 10-16 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Synthesis of new liquid phases ; Evaluation of new phases
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Three columns, mono-ol, butylphenyl and perfluorinated synthesized through the reaction of an olefin with a silica hydride intermediate, are evaluated for the separation of various model compounds. Two of the columns, mono-ol and perfluorinated, can operate in both the normal phase and reversed phase modes. Some effects of the hydride surface are detected, particularly for the perfluorinated phase. A four-component steroid mixture is tested on both the mono-ol and perfluorinated phases in the normal mode.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02272815
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  • 6
    Digitale Medien
    Digitale Medien
    Synthesis and characterization of long chain alkyl stationary phases on a silica hydride surface (1998)
    Springer
    Chromatographia 48 (1998), S. 631-636 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Synthesis of new phases ; Evaluation of new phases
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary C22 and C30 alkyl chains were attached to a silica hydride surface by a hydrosolation reaction. In each case both moieties were successfully bonded by either metal complex catalysis or free radical initiation. Carbon analysis, DRIFT spectra and13C CP-MAS NMR spectra confirm the bonding of the olefin to silica hydride. Conditions for maximum coverage were determined by a simplex procedure. Chromatographic evaluation of these long chain bonded phases was accomplished by separations of several types of mixtures: alkyl substituted benzenes; polycyclic aromatic hydrocarbons; carotenoids, tocopherols; tricyclic antidepressants; and peptides. The C30 column proved significantly better for separating the carotenoid and antidepressant mixtures and somewhat better for the peptide sample.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467592
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  • 7
    Digitale Medien
    Digitale Medien
    Synthesis of chemically bonded squalene(ane) phases for microcolumn gas chromatographic separation of low-molecular-weight hydrocarbons in extraterrestrial atmospheres (1996)
    Springer
    Chromatographia 42 (1996), S. 141-146 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Low-molecular-weight hydrocarbons ; Extraterrestrial atmospheres ; Chemically bonded squalene(ane) phase ; 13C and29Si CP-MAS NMR
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Chemically bonded squalene(ene) phases have been synthesized via a hydride modified silanization process using dimethylchlorosilane, triethoxysilane and trichlorosilane. The surface structure of the bonded phases were characterized with DRIFT and solid state NMR studies. The results of the latter indicate successful bonding of a non-terminal olefin to the silica surface and that bonding of individual squalene molecules appeared not to occur at the same site(s) presumably due to steric hindrance. Among the phases examined, the trichlorosilane-based material exhibits better chromatographic properties probably due to greater surface coverage and hence effective non-polar interaction between the solutes and the bonded ligands. Under isothermal conditions, the present packings produced fast and efficient separation of C1–C4 saturated hydrocarbons on shorter columns than similar columns containing alkyl- or bidentate alkyl-modified silica packings at low column head pressure and are thermally stable at temperatures up to 250°C or higher.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269643
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  • 8
    Digitale Medien
    Digitale Medien
    Polyfunctional chemically bonded stationary phase for reversed phase high-performance liquid chromatography (1998)
    Springer
    Chromatographia 48 (1998), S. 615-622 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Synthesis of polyfunctional stationary phases ; Quantitative structure-retention relationships, QSRR ; Separation of steroids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Preparation of a chemically-bonded-silica stationary phase (SG-MIX), with different polar and nonpolar functional groups such as hydroxyl (-OH), amino (-NH2), cyano (-CN), phenyl (-Ph), octyl (-C8) and octadecyl (-C18), is described. The characteristics of the prepared packing was done by physicochemical methods such as elemental analysis, FTIR spectroscopy, solid-state nuclear magnetic resonance (NMR), chromatography (GC and HPLC) as well as by analysis of quantitative structure-retention relationships (QSRR). The polyfunctional SG-MIX phase possesses properties of a reversed-phase material modified by specific inputs to retention due to interactions of analytes with polar functionalities on the surface of adsorbent. The new type of packing was successfully used for both analytical and preparative separation of finasteride from its metabolite, N-methylfinasteride.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467590
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  • 9
    Digitale Medien
    Digitale Medien
    Comparison of octadecyl bonded titania phases (1999)
    Springer
    Chromatographia 49 (1999), S. 424-430 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Octadecyl titania ; Surface hydrosilation ; Solid-state NMR C7
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The structure of a C18 phase based on titania (C18-A), synthesized by the method of solution polymerization, is investigated by diffuse reflectance infrared Fourier transform (DRIFT) and solid-state nuclear magnetic resonance (NMR) spectroscopy. The findings are compared with the results of a second C18 phase based on titania (C18-B) which was synthesized by the method of surface hydrosilation. The dynamic behavior of both phases is examined by1H MAS NMR detection of spinlattice relaxation times in the rotating frame (T1pH) and conventional spin-lattice relaxation times (T1). Due to a smaller ligand density, phase C18-A appears to be a somewhat more mobile than phase C18-B. The chromatographic capability of the phase C18-A is demonstrated by the separation of samples containing benzene derivates or anilines. The elution order is analogous to the phase C18-B, but for both test mixtures the polarity of the mobile phase has to be increased. Phase C18-A is classified as being polymeric by the Sander and Wise test, whereas phase C18-B shows intermediate retention behavior.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467618
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