Anion selectivity at the aqueous/polymeric membrane interface: A streaming current study of potentiometric Hofmeister effect

作者：Wojciechowski Kamil^*; Linek Kamil

来源：Electrochimica Acta, 2012, 71: 159-165.

DOI：10.1016/j.electacta.2012.03.113

• ISE
• Hofmeister effect
• Zeta potential
• Ion-specificity

The anion-selectivity of model polymeric membranes as used in potentiometric sensors (ion-selective electrodes, ISE) was studied using zeta-potential measurements. For this purpose the streaming current measurements of plasticized poly(vinyl chloride) were performed by pushing an aqueous electrolyte through a thin channel with walls lined with the polymer. Despite the literature reports on accumulation of plasticizer on the PVC membrane surface, no significant effect of plasticizer on the potential vs pH curve was observed. A cationic surfactant, cetyltrimethylammonium bromide (CTAB) was chosen as a water-soluble analogue of tetraalkylammonium salts used in anion-selective ISE displaying a characteristic Hofmeister selectivity pattern. The effect of anions on zeta-potential was studied at fixed concentration of CTAB (10(-4) mol L-1 approximate to 0.1 cmc), by varying the concentration and nature of anion in the added 1:1 electrolytes (NaCl, NaBr, NaF, NaClO4, Nal and NaNO3). The anions chosen cover the whole Hofmeister series, and their influence on the measured zeta-potential parallels that of the Hofmeister effect in potentiometry, as well as in colloid/interface science. A significant deviation was observed only for fluoride ions. The effect of anion selectivity on zeta-potential is clearly notable, but rather weak, due to a large distance between the location of the Stern layer (where the ion-specific interactions take place), and that of the hydrodynamic slip plane (where the zeta-potential is actually measured).

• 出版日期2012-6-1