ISSN:
1432-1130
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Potentiometric and electrochemical impedance spectroscopic investigations of calcium-selective membranes containing poly(vinylchloride), dioctylphenylphosphonate, calcium (bis[4-(1,1,3,3-tetramethylbutyl)phenyl] phosphate) and different amounts of the lipophilic anionic additive tridodecylmethylammonium chloride were carried out. The addition of the lipophilic additive changes the properties of calcium-selective electrodes, e.g. slope and calcium selectivity. The selectivity for calcium in presence of H+, Na+, K+, NH4 +, Mg2+, Ba2+, Sr2+ and (C2H5)4N+ was measured by three different methods, namely separate solution method, fixed interference method and matched potential method. Membranes with different concentration ratios between the calcium-exchanger and tridodecylmethylammonium chloride were investigated within half a year. The tendency of changing from cationic into anionic response for membranes containing nearly equivalent concentrations of cation- and anion-exchanger was shown. This inversion of the electrode response depends not only upon the concentration ratio of both ion-exchangers but also upon the total concentration of calcium-exchanger. Electrochemical impedance spectroscopy was used for monitoring the development of membrane resistances during a soaking period of one month. Based on these results dielectric constants for the calcium-selective membranes depending on the membrane composition were determined. Furthermore, the dependence of the membrane resistance on the membrane thickness and the concentration of tridodecylmethylammonium chloride was evaluated.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002160051205
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