Apparently "non-nernstian" equilibrium responses based on complexation between the primary ion and a secondary ion in the liquid ISE membrane

Philippe Bühlmann, Yoshio Umezawa

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

We have previously reported on a phase boundary model explaining the apparently "twice-Nernstian" responses to divalent cations as they have been observed for some liquid-membrane ion-selective electrodes (ISEs) based on acidic ionophores. The rationalization of those responses which are characterized by slopes that are two times larger than Nernstian response slopes for divalent cations, took into account the equilibrium distribution of two types of ions, i.e., the divalent cations as primary ions and H+ ions as "secondary ions", across the sample-membrane interface. In the present work, we have intentionally chosen an extremely simple type of electrodes to show that apparently "non-Nernstian" responses can also occur if the primary and the secondary ion have opposite charge signs. It is shown that apparently "non-Nernstian" equilibrium responses can occur in the case of ionophore-free ion-exchanger electrodes if the sample solutions contain besides the primary ion also a secondary ion, and if 1:n or n:1 complexes between these two types of ions are formed in the electrode membrane phase. In contrast to the well-known responses of ion-exchanger electrodes in solutions that contain metal ion complexes, an interaction between the primary and secondary ion in the sample solution is not required for the observation of apparently "non-Nernstian" equilibrium responses. A set of very simple equations allows the determination of the response slopes that are expected for particular sets of complex stoichiometries and charges of the primary and secondary ion. Due to the very general formulation of the theory these results are applicable both for electrodes with primary and secondary ions of opposite charge signs and for electrodes with primary and secondary ions of the same charge sign.

Original languageEnglish (US)
Pages (from-to)687-693
Number of pages7
JournalElectroanalysis
Volume11
Issue number10-11
DOIs
StatePublished - Jul 1999

Keywords

  • Ion-selective electrode
  • Non-nernstian response
  • Primary ion
  • Response slope
  • Secondary ion
  • Super-nernstian response
  • Twice-nernstian response

Fingerprint Dive into the research topics of 'Apparently "non-nernstian" equilibrium responses based on complexation between the primary ion and a secondary ion in the liquid ISE membrane'. Together they form a unique fingerprint.

Cite this