Hydration energy or hydration force? Origin of ion-specificity in ion selective electrodes

Kamil Wojciechowski

Abstract

The origin of ion-specificity (also known as Hofmeister effect) in potentiometric ion selective electrodes (ISE) with polymeric membranes has been traditionally assigned to the differences in lipophilicities of ions, with hydration energies described in the framework of Born theory as being of purely electrostatic nature. This is in clear contrast to the current understanding of the Hofmeister effect in colloid and interface science, where it is viewed as resulting from an interplay between the electrostatic and non-electrostatic interactions, the latter often referred to as “hydration” forces. The two approaches to ion-specificity in ISE, simplistically termed “hydration energy” (ion partitioning between an aqueous phase and the ISE membrane) and “hydration force” (ion adsorption from an aqueous phase to the electrically charged ISE membrane) are described and compared. Two major conclusions are drawn: i) ion-specificity can be included in both approaches, although it is more natural within the “hydration force” approach with ion-surface interactions; ii) both ion partitioning into, and ion adsorption onto the ISE membrane should be considered in order to fully understand the origin of ion-specificity in ISE.
Author Kamil Wojciechowski ZMB
Kamil Wojciechowski,,
- Department Of Microbioanalytics
Journal seriesCurrent Opinion in Colloid & Interface Science, ISSN 1359-0294
Issue year2011
Vol16
No6
Pages601-606
Keywords in EnglishHofmeister effect, ion selective electrodes
DOIDOI:10.1016/j.cocis.2011.05.002
URL http://www.sciencedirect.com/science/article/pii/S1359029411000719
Score (nominal)40
Publication indicators WoS Impact Factor [Impact Factor WoS]: 2011 = 8.01 (2) - 2011=7.837 (5)
Citation count*4 (2014-04-22)
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