Ionic condensation of sodium chondroitin sulfate in water–dioxane mixture (original) (raw)

Journal of Molecular Liquids, 2007

Abstract

In a previous work, we have verified that sodium chondroitin sulfate in water at 25 °C, presents a correct Manning behavior (αM=0.81). In contrast, we expect that the rate of condensation α is shifted from its Manning value (αM=0.36) in water–dioxane (50% wt) mixture at 25 °C, (α≅0.47). In order to verify this dioxane effect, we have compared experimental equivalent conductibility Λexp of sodium chondroitin sulfate in water (no shift) and water–dioxane (50% wt) mixture (positive shift), to their theoretical values ΛM, Λcth and Λsth corresponding respectively to the Manning cylindrical and spherical models. Indeed, except some cases, α must obey to Ostwald's principle of dilution (α→1 when CNa+→0), according to the following “rod-like model” approximation:(1−α)≈|Zi|(πbS)[4⁢πZi2Lb][−bS″α][αCiR2][1−bS″α];with:bS″=αM−1However, only in pure water at 25 °C (ε=78.3), the exponent [1−bS″α] of sodium chondroitin sulfate is zero and therefore: α=αM.

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