Intrinsic binding effects in mixed counterionic polyelectrolyte systems: extension of condensation theory and comparison with voltammetric data (original) (raw)
1995, Biophysical Chemistry
Voltammetric speciation data for the potassium/zinc/polymethacrylate system, recently obtained for various charge densities of the polyelectrolyte (Díaz-Cruz et al., Anal. Chim. Acts, 264 (1992) 163) and for different concentrations of monovalent counterions (van den Hoop and van Leeuwen, Anal. Chim. Acts, 273 (1993) 275), are compared with theoretical predictions computed according to a new thermodynamic model developed by Paoletti et al. (Biophys. Chem., 41 (1991) 73) and recently extended by Benegas and Paoletti (in preparation). The model allows: (i) the simultaneous condensation of both monovalent and divalent counterions and (ii) can account for a certain specific affinity of the polyelectrolyte for one type of the counterion over the other. For various charge densities of the polyelectrolyte, experimentally obtained speciation data for the K/Zn/PhU system agree wel1 with theoretical predictions by considering an extra reduced molar affinity energy of -4RT for the Znz+ polyelectrolyte binding. The agreement between experimental and theoretical values for the distribution of Zn*+ ions over the free and bound state becomes less perfect for relatively high concentrations of monovalent counterions. chemical and/or physical-chemical farms in natura1 0301-4622/95/$09.50 0 1995 Elsevier Science B.V. Al1 rights reserved SSDI 0301-4622(94)00125-1
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