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  • Calculation of concentration of organic modifier  (2)
  • distribution  (2)
  • electrical conductivity  (2)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 262 (1984), S. 477-480 
    ISSN: 1435-1536
    Schlagwort(e): Dielectric property ; permittivity ; electrical conductivity ; ion-exchanger ; interfacial polarization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 263 (1985), S. 428-432 
    ISSN: 1435-1536
    Schlagwort(e): Dielectric property ; dielectric relaxation ; permittivity ; electrical conductivity ; ion-exchanger
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 269 (1991), S. 880-888 
    ISSN: 1435-1536
    Schlagwort(e): Dielectricrelaxation ; distribution ; microcapsule ; permeability ; porassiumchloride
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Release of KCl from a batch of PMMA microcapsules containing an aqueous 3 mM KCl solution was studied with the following two methods: 1) dielectric measurements of suspensions of the microcapsules in distilled water. The electrical conductivity of capsule interior was estimated with this method. 2) Measurements of the conductivity of suspending medium of the microcapsule suspensions. These two kinds of experiments provided us with information about the amount of KCl remaining in the capsules and that diffused outside. Results of these experiments showed that the microcapsules varied in their release rate of KCl. A distribution function of the release rates was derived from the results of the dielectric measurements. That distribution function was successful in explaining the results of the measurements of the conductivity of suspending medium. Furrther examination revealed that the release rate increased with the increase in the thickness of capsule wall.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 268 (1990), S. 1059-1065 
    ISSN: 1435-1536
    Schlagwort(e): Dielectricproperty ; distribution ; microcapsule ; suspension
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Theoretical consideration is made concerning the dielectric behavior of aqueous suspensions of W/O-type microcapsules containing aqueous electrolyte solutions, especially concerning distribution effects of the electrolyte release rate on the dielectric behavior. It is shown at first that the distribution of the release rate causes electrical conductivity of the capsule interior. Next, it is deduced, in the light of a theory of the interfacial polarization, that the distribution characteristics of the capsule interior's electrical conductivity are closely related to those of the relaxation time for a dielectric relaxation exhibited by the suspensions. Several formulas are derived to describe the relation between the distribution characteristics of the release rate and those of the relaxation time.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 6 (1983), S. 20-26 
    ISSN: 0935-6304
    Schlagwort(e): Reversed-phase mode liquid chromatography ; Rekker's hydrophobic fragmental constant ; Calculation of concentration of organic modifier ; Prediction of retention time of phenols ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The chromatographic behavior of phenols in reversed-phase mode liquid chromatography differs from that of non-ionic compounds such as alkyl alcohols, alkylbenzenes, halogenated benzenes, polyaromatic hydrocarbons, and aromatic acids. Therefore, the retention times of 61 phenols were measured in a system of an octadecyl bonded silica gel and acetonitrile/water mixtures. The logarithm of the capacity ratio (log k') was found to be a linear function of the hydrophobicity (log P) in acidic acetonitrile/water mixtures. This result was applied to a different octadecyl bonded silica gel. Eight phenols were selected as standard compounds, and their log k' values were measured in 0.05 M phosphoric acid in 10 to 90% acetonitrile/water mixtures. An empirical polynomial relation was obtained between the concentration of acetonitrile and the slope of the log k' vs log P curve. Finally the capacity ratio of all phenols were calculated in given eluents by the equations derived from the measurements of standard compounds and the calculated log P values. The difference between predicted capacity ratios and measured ones was within 10%.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 4 (1981), S. 454-460 
    ISSN: 0935-6304
    Schlagwort(e): Reversed-phase mode liquid chromatography ; Rekker's hydrophobic fragmental constant ; Calculation of concentration of organic modifier ; Prediction of retention time ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The utility of Rekker's hydrophobic fragmental constant has been examined for optimization of reversed-phase mode liquid chromatographic separations. The chromatographic behavior of about 60 non-ionic compounds was measured in different acetonitrile/water mixtures and the logarithm of their capacity factors (log k) was correlated with their calculated hydrophobicities (log P). Linear relations were found in each case between log k and log P. The slope of the various lines was related to the percentage concentration of acetonitrile in the mobile phase. It was shown that, by using nine stand ard compounds and measuring their capacity factors in five eluents with different acetonitrile concentrations, the retention time could be predicted for 60 compounds. Calculation of the concentration of the organic modifier was also possible in a system of well coated octadecyl bonded packings with acetonitrile/water mixtures as eluent. Prediction of the capacity factor was accomplished to within 5% error.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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