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  • 1
    Electronic Resource
    Electronic Resource
    Intermolecular interactions in liquid adsorption chromatography (1983)
    Springer
    Chromatographia 17 (1983), S. 143-148 
    Details
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Intermolecular interactions ; Adsorption from solutions ; Chemically modified layers in LC ; Conformation of bonded chains
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary For the investigation of intermolecular interactions in adsorption from solution, which are the basis of selectivity in molecular liquid chromatography (LC), it is convenient to use the LC method itself. Using this method the Henry's constants, K1, and other thermodynamic adsorption characteristics of hydrocarbons and of a series of polar substances on hydroxylated silica surface were determined from aqueous solutions. On the basis of the adsorption of hydrocarbons from water solutions the structure of the chemically modifying layers formed by different hydrocarbon groups on the silica surface is considered. The role of conformation ability of straight-chain bonded phases is demonstrated. Hydrocarbons are adsorbed on the hydroxylated silica surface more strongly from aqueous solutions than from solutions in saturated hydrocarbons and their retention increases with the increase in the number of carbon atoms in the molecule. The retention in LC is determined by the intermolecular interaction of the solute and solvent molecules with the adsorbent, as well by the contribution of the intermolecular interaction, between the solute and the solvent. The thermodynamic characteristics of adsorption of cymarin from water-ethanol solutions on hydroxylated silica gel and on silica gel surface modified by diphenylsilyl groups is compared. The solubility of silica gel modified by diphenylsilyl groups at different composition of water-ethanol eluent at different temperatures is investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02271037
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  • 2
    Electronic Resource
    Electronic Resource
    Regularities in the retention of nonsubstituted polynuclear aromatic hydrocarbons in liquid chromatography on polar adsorbents (1985)
    Springer
    Chromatographia 20 (1985), S. 533-537 
    Details
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Polyaromatic hydrocarbons ; Polar stationary phase ; Relationship between retention and molecular structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention of polynuclear aromatic hydrocarbons (PAH) is studied in liquid chromatography, using columns packed with silica gel with a hydroxylated surface and the same silica gel with surface-bonded amine and nitrile groups. A linear relationship was found between retention and the number of π-electrons in the molecule, the size of the molecule and the different types of carbon atoms in the molecule. The different carbon atoms in a PAH molecule contribute differently to the retention and this contribution depends on the nature of the polar functional groups on the adsorbent's surface and on the nature and concentration of a polar modifier present in a non-polar eluent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02312172
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  • 3
    Electronic Resource
    Electronic Resource
    Physico-chemical applications of liquid chromatography I. Investigation of the adsorption of cardiac glycosides from water-ethanol solutions on silanized silica (1980)
    Springer
    Chromatographia 13 (1980), S. 745-751 
    Details
    ISSN: 1612-1112
    Keywords: Adsorption from solutions ; Liquid chromatography ; Cardiac glycosides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Using the cardiac glycoside cymarin as the example the application of liquid chromatography for the study of adsorption from solutions and the determination of the corresponding thermodynamic characteristics was investigated. The adsorption isotherm of cymarin at small concentrations from a water-ethanol solvent on silica gel modified by dimethyldichlorosilane was measured under static conditions using analytical LC to determine the concentrations of solutions after adsorption. The values of the Henry constants were obtained by extrapolating the slope of the adsorption isotherm down to zero concentration. The specific retention volumes for different but small sample sizes of cymarin in the chromatographic column were measured, the adsorbent and the water-ethanol eluent being the same as in the static conditions. The specific retention volume for a small (zero) sample size determined by liquid chromatography experiment coincides with the Henry constant of cymarin adsorption determined in static conditions. In favourable cases liquid chromatography can be used to determine the equilibrium constants for adsorption from solution. The dependence of the Henry constants on temperature was investigated for several cardiac glycosides. The influence of the modification of the adsorbent surface on the separation of the cardiac glycosides was also studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02265553
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  • 4
    Electronic Resource
    Electronic Resource
    Liquid chromatography of benzene derivatives on a porous methacrylate copolymer containing epoxy groups (1983)
    Springer
    Chromatographia 17 (1983), S. 545-548 
    Details
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Porous copolymer containing epoxy groups ; Retention of nonpolar and polar benzene derivatives ; Dipole moment and liquid chromatography retention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention of benzene derivatives with nonpolar and polar substituents on a porous methacrylate copolymer containing epoxy groups using both nonpolar and polar eluents was investigated. When n-hexane is used as the eluent, the retention of n-alkylbenzenes and polymethylbenzenes is weaker than that of benzene. In the case of benzene derivatives containing polar functional groups their capacity ratios (k) on this porous polymer increases approximately linearly with the increase of the adsorbate molecules dipole moment. The retention characteristics of the methacrylate copolymer were compared with that of a styrene-divinylbenzene copolymer and silica gels with a hydroxylated surface and with a surface modified by chemically bonded alkylsilyl groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02261917
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  • 5
    Electronic Resource
    Electronic Resource
    Separation of unsaturated and aromatic hydrocarbons on capillary columns packed with barium sulphate (1985)
    Springer
    Chromatographia 20 (1985), S. 519-524 
    Details
    ISSN: 1612-1112
    Keywords: Gas adsorption chromatography ; Packed capillary columns ; Modification of BaSO4 ; Separation of isomeric unsaturated and aromatic hydrocarbons ; Selectivity and dipole moment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Isomeric hydrocarbons with molecules having similar geometry but differing in the electron density distribution were separated on capillary columns packed with barium sulphate, a non-porous ionic adsorbent. Samples of BaSO4 were washed free of foreign ions and modified by solutions of alkaline metal halides. The selectivity of the separation of unsaturated and aromatic hydrocarbons can be controlled by varying the conditions of the BaSO4 treatment. Capillary columns packed with the ionic adsorbent were successfully used to separate all xylene and butene isomers, as well as isomers of cis and trans octene-2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02312169
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  • 6
    Electronic Resource
    Electronic Resource
    Physico-chemical applications of liquid chromatography II. Investigations of the surface properties of chemically modified silica gels and of the adsorption of cardiac glycosides from solutions (1981)
    Springer
    Chromatographia 14 (1981), S. 13-18 
    Details
    ISSN: 1612-1112
    Keywords: Chemical modification of silica ; Liquid chromatography ; Cardiac glycosides ; Chromatographic investigation of adsorption from solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chemical modification of silica surface using dichlorosilanes with methyl and phenyl groups and triethylamine as donor in the liquid phase was investigated. This modification leads to a dense coverage of the silica surface by the organic functional groups. Liquid chromatography permits the determination of the thermodinamic characteristics of intermolecular interactions of different molecules during adsorption from solutions on the modified surface of the silica. Silica gels modified with dichlorosilanes containing phenyl groups, possess high selectivity (α) and capacity (k′) for the cardiac glycosides G-strophanthin, K-strophanthoside, K-strophanthin-β and cymarin using water-alcohol mixture as the mobile phase, and the selectivity and capacity is much higher than observed on silica gels modified with methyl groups only.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262056
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  • 7
    Electronic Resource
    Electronic Resource
    Chromatographic determination of the thermodynamic adsorption characteristics of saturated tricyclic hydrocarbon isomers using capillary columns with graphitized carbon black (1983)
    Springer
    Chromatographia 17 (1983), S. 533-538 
    Details
    ISSN: 1612-1112
    Keywords: Gas adsorption chromatography ; Molecular structure and adsorption ; Graphitized carbon black ; Capillary packed adsorption columns ; Tricyclic hydrocarbon separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Due to their high efficiency capillary columns packed with graphitized thermal carbon black (GTCB) permit to realize high selectivity in the chromatographic separation of isomers on the flat surface of this adsorbent. However, the increase in the efficiency is connected to a considerable increase of the pressure drop across the column which hinders the determination of the thermo-dynamic adsorption characteristics. The optimum conditions for the preparation of such columns designed both for analytical purposes and for thermodynamic measurements of the individual isomers have been established. The retention volumes for small (zero) sample size (Henry constants for adsorption on GTCB) of six isomers of tricyclo(8,4,0,02,7)tetradecane (perhydrophenanthrene), seven isomers of tricyclo-(7,4,0,02,6)tridecane (1,2-cyclopentanodecalin) and six isomers of tricyclo(7,3,0,02,6)dodecane have been determined. The Henry constants increase with the flattening of the isomeric molecules in these hydrocarbon series. A qualitative procedure of identification of the isomers on the basis of optimum orientation of their molecules on a flat surface has been considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02261915
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  • 8
    Electronic Resource
    Electronic Resource
    Die Retention von Indan- und Inden-Kohlenwasserstoffen auf graphitiertem thermischen Ruß (1980)
    Springer
    Chromatographia 13 (1980), S. 493-496 
    Details
    ISSN: 1612-1112
    Keywords: Gas adsorption chromatography ; Graphitized thermal carbon black ; Indan ; Indan-type hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es werden die Werte der Retentionsvolumina, der Retentionsindices und andere thermodynamische Adsorptionscharakteristiken von zehn Indan- und Inden-Kohlenwasserstoffen mit 9–11 Kohlenstoffatomen auf graphitiertem thermischem Ruß (GTR) bestimmt. Es wurde festgestellt, daß auf GTR die Kohlenwasserstoffe der Inden-Reihe am stärksten adsorbiert werden und am schwächsten cis-Hydrandan, was mit den Besonderheiten der geometrischen Struktur dieser Verbindungen zusammenhängt. Es wird die Möglichkeit der Anwendung von GTR für die vollständige Trennung der cis- und trans-Isomeren von Hydrindan gezeigt.
    Notes: Summary The retention volumes, retention indices and other thermodynamic values characteristic of the adsorption of ten indan-hydrocarbons having 9–11 carbon atoms were determined on graphitized thermal carbon black (GTCB). It is shown that GTCB adsorbs strongest the hydrocarbons of the indan series and weakest cis hydrindan. This is related to the peculiarities of the geometric structure of the compounds. The possibility of the application of GTCB for the complete separation of cis and trans hydrindan is shown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02261620
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  • 9
    Electronic Resource
    Electronic Resource
    Regularities in the retention of isomeric aromatic hydrocarbons in liquid chromatography II. Analysis of polymethyl- and monoalkylbenzenes on silanized silica gel (1981)
    Springer
    Chromatographia 14 (1981), S. 638-640 
    Details
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Aromatic hydrocarbons ; Molecular structure ; Influence on retention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The regularities of the retention of polymethyl- and monoalkylbenzenes on a nonpolar adsorbent (silanized silica gel) with a polar eluent (2∶3 isopropanol-water) have been studied. In contrast to the retention of the same compounds on a polar adsorbent (silica gel with hydroxylated surface) and with a nonpolar eluent (hexane) polymethylbenzenes are retained on silanized silica gel for a shorter time than the corresponding monoalkylbenzene isomers. The retention order of tert.-, sec.- and n-butylbenzenes is the reverse of that observed on silica gel having a hydroxylated surface. The retention order of xylenes, trimethyl- and tetramethylbenzenes is also the reverse of their retention order on silica gel having a hydroxylated surface. All the mixtures of the corresponding homologues and isomers have been separated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02291103
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  • 10
    Electronic Resource
    Electronic Resource
    Separation of carbohydrates by liquid chromatography on silica gel, adding adsorption modificators to the eluent (1982)
    Springer
    Chromatographia 15 (1982), S. 751-756 
    Details
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Carbohydrates ; Bonded-phase columns ; Silica gel modified with amino groups
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary For the separation of carbohydrates by liquid chromatography, utilizing the intermolecular interaction with amino groups on the surface of the adsorbent, two types of adsorbents were used: silica gel modified by adding to the eluent a diamine, and a chemically bonded phase prepared by the reaction of γ-aminopropyl triethoxy silane with silica gel. Mono- di- and trisaccharides could be separated on silica gel modified by the adsorption of piperazin and ethylene diamine from the eluent. The separation capacity of columns packed with silica gel with bonded NH2 groups and with silica gel having diamines adsorbed on its surface is similar. The retention volumes of 15 carbohydrates were measured on columns containing silica gel with hydroxylated surface and on silica gel modified with piperazin from the eluent consisting of acetone-water. Comparison of acetone-water and acetonitrile-water as the eluent showed that the former is also suitable for the analysis of carbohydrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02261370
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