The Origin of the Non-Constancy of the Bulk Resistance of Ion-Selective Electrode Membranes within the Nernstian Response Range

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Abstract

The dependence of the bulk resistance of membranes of ionophore-based ion-selective electrodes (ISEs) on the composition of mixed electrolyte solutions, within the range of the Nernstian potentiometric response, is studied by chronopotentiometric and impedance measurements. In parallel to the resistance, water uptake by the membranes is also studied gravimetrically. The similarity of the respective curves is registered and explained in terms of heterogeneity of the membranes due to the presence of dispersed aqueous phase (water droplets). It is concluded that the electrochemical equilibrium is established between aqueous solution and the continuous organic phase, while the resistance refers to the membrane as whole, and water droplets hamper the charge transfer across the membranes. In this way, it is explained why the membrane bulk resistance is not constant within the range of the Nernstian potentiometric response of ISEs.
Original languageEnglish
Article number344
Number of pages13
JournalMembranes
Volume11
Issue number5
StatePublished - 7 May 2021

Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)

Keywords

  • ion-selective membranes
  • Ionophores
  • mixed aqueous solutions of electrolytes
  • resistance
  • water uptake
  • nanometer-sized water droplets
  • potentiometry
  • chronopotentiometry
  • Electrochemical impedance
  • gravimetry

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