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  • 1
    Electronic Resource
    Electronic Resource
    Dielectric properties of ion-exchange beads of sulfonic acid type dispersed in aqueous solutions — effect of fixed charge density (1985)
    Springer
    Colloid & polymer science 263 (1985), S. 428-432 
    Details
    ISSN: 1435-1536
    Keywords: Dielectric property ; dielectric relaxation ; permittivity ; electrical conductivity ; ion-exchanger
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Ion-exchange beads with different densities of fixed charges were prepared by sulfoethylation of dextran gel beads. The relative permittivities and the electrical conductivities of the ion-exchange beads in a sodium form were evaluated by a dielectric technique consisting of the following two procedures proposed in a previous study (2): (a) Dielectric measurements for densely packed sediments of the ion-exchange beads; (b) Analysis of the observed dielectric relaxations by means of a theoretical equation of interfacial polarization for suspensions of spherical particles. The deduced permittivities of the ionexchange beads in equilibrium with water were about 60, which is lower than those of outer aqueous phases. The deduced conductirities were of the order of 1 to 10 mS cm−1 and were increased reasonably with the fixed charge density. Closer consideration on these deduced values indicates that no specific interaction exists between the counter ions and the fixed charges irrespective of changes in fixed charge density and temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01410394
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  • 2
    Electronic Resource
    Electronic Resource
    Dielectric observations on polystyrene microcapsules and the theoretical analysis with reference to interfacial polarization (1983)
    Springer
    Colloid & polymer science 261 (1983), S. 381-389 
    Details
    ISSN: 1435-1536
    Keywords: Conductivity ; Dielectric property ; Dielectric relaxation ; Interfacial polarization ; Microcapsule ; Permittivity ; Polystyrene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Dielectric measurements were carried out for polystyrene microcapsules which were prepared by means of an interfacial polymer deposition technique. The microcapsules showed a couple of dielectric relaxations termedP for lower andQ for higher frequencies. The frequency profiles were characteristic of the structure that shelled spheres were dispersed in a continuous medium. Gelatin aqueous solutions, cationic polyelectrolyte solutions and distilled water were loaded in the capsule interior to examine the effect of conductivities of the constituent aqueous phases on the dielectric properties. Relaxation frequencies of the relaxationsP andQ observed were directly proportional to the conductivities of the continuous medium and of the capsule interior, respectively. A dielectric theory was proposed for a suspension of shelled spheres in a continuous phase in order to analyze the relaxation data observed for the microcapsules. Volume fraction of the capsules, relative permittivity and conductivity of the capsule interior and thickness of the capsule wall are evaluated from the dielectric observations by use of the theoretical formulas derived. The dielectric behavior observed for the polystyrene microcapsules are interpreted quantitatively in terms of the dielectric theory proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01418210
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Dielectric properties of quaternary ammonium ion-exchange beads dispersed in aqueous phases (1984)
    Springer
    Colloid & polymer science 262 (1984), S. 477-480 
    Details
    ISSN: 1435-1536
    Keywords: Dielectric property ; permittivity ; electrical conductivity ; ion-exchanger ; interfacial polarization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Dielectric measurements were carried out for dense sediments of quaternary ammonium type anion-exchange resin beads dispersed in deionized water over a frequency range of 30 Hz to 130 MHz. According to a method proposed in previous studies the relative permittivities and electrical conductivities of ion-exchange beads were evaluated from the relaxation data observed in a megahertz region on the basis of a theory of interfacial polarization. The permittivities of the ion-exchange beads were found to be unchanged irrespectively of the salt form and somewhat lower than that of a continuous medium, while the conductivities of the ion-exchange beads were characteristic of the salt form. The equivalent ionic conductances of different counter anions in the beads were estimated from the conductivities of the ion-exchange beads. These results indicate an ion-binding effect in the resin beads.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01412044
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  • 4
    Electronic Resource
    Electronic Resource
    Dielectric approach to polystyrene microcapsule analysis and the application to the capsule permeability to potassium chloride (1984)
    Springer
    Colloid & polymer science 262 (1984), S. 513-520 
    Details
    ISSN: 1435-1536
    Keywords: Dielectric property ; dielectric relaxation ; microcapsule ; permittivity ; polystyrene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A method of numerical analysis is proposed to determine the phase parameters from dielectric observations of polystyrene microcapsules by using the conductivity at intermediate frequencies between two dielectric relaxations observed. The method was more feasible for the analysis of the microcapsule observations than the method by which the calculation is performed by use of the permittivity at lower frequencies. The method was applied to the dielectric observations of the KCl-loaded microcapsules to obtain the permittivity and the conductivity of the capsule interior, the thickness of the capsule wall, the volume fraction of the suspended capsules and the conductivity of the surrounding aqueous phase. The conductivity of capsule interior was found to be unchanged with time for as long as 3 months. From the results it is concluded that the microcapsules are impermeable to KCl.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01451514
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  • 5
    Electronic Resource
    Electronic Resource
    Chromatographic behaviour of acids on macro-porous-polystyrene gels (1983)
    Springer
    Chromatographia 17 (1983), S. 633-639 
    Details
    ISSN: 1612-1112
    Keywords: Macro porous polystyrene gel and the ion-exchange resins ; Aromatic acids ; Hydrophobicity ; Dissociation constant ; lon-pair
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention behaviour of aromatic acids was examined in a reversed-phase mode liquid chromatography. Macro porous styrene-divinylbenzene copolymers were selected on the basis of their chemical stability throughout the entire pH range. The effect of addition of a hydrophobic ion in the eluent and that of an ion-exchange group on the packing were discussed in relation with the hydrophobicity and the dissociation constant of solutes. The maximum capacity ratios of the acids on apolystyrene gel are linearly related with the hydrophobicity. The prediction of the retention time of aromatic acids could be possible by combination of their hydrophobicity and their dissociation constants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02261948
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Optimization of retention time of aromatic acids in liquid chromatography from log P and predicted pKa valuesThis paper was presented at VIIth International Symposium on Column Liquid Chromatography, Baden-Baden, May (1983) (1984)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 7 (1984), S. 524-528 
    Details
    ISSN: 0935-6304
    Keywords: Liquid chromatography, HPLC ; Reversed phase mode ; Prediction of retention time ; Prediction of pKa ; Hydrophobic fragmental constant ; Aromatic acids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For optimization of liquid chromatography separations, several approaches have been reported, among them the use of the hydrophobic fragmental constant, as proposed by Rekker [1]. The fragmental constant is derived from the partition coefficients of various solutes between octanol and water and represents a summation of solubility parameters: van der Waals volume, π - π interactions, hydrogen bonding, etc. With these constants the optimization of reversed phase mode liquid chromatography using octadecyl bonded silica gels as packing was feasible, although large error was found for the eluent with a high concentration of organic modifier or water. This is probably due to the heterogeneous solvation of the surface of the packings and to various solvent effects. In addition, when the acid dissociation constant was known, the retention times of aromatic acids in the ionic form were also predicted using the hydrophobic fragmental constant and the dissociation constant. By comparison of the previous data and a method proposed by Perrin et al. [2] it was possible to predict the dissociation constant of aromatic acids and optimize separation in reversed phase mode liquid chromatography using octadecyl bonded silica gels as packing. Furthermore, an equation for calculating the capacity ratios in a given pH eluent was proposed and the predicted and observed capacity ratios of aromatic acids in several eluents were examined in order to improve the above system.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240070906
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