Cleaning of pH Selective Electrodes with Ionophore-doped Fluorous Membranes in NaOH Solution at 90 °C

Elizabeth C. Lugert-Thom, John A. Gladysz, J. Rábai, Philippe Bühlmann

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

This work demonstrates the remarkable stability of fluorous ion-selective electrode (ISE) membranes by exposing them to cleaning-in-place treatments (CIP) as they are used in many industrial processes. The sensing membranes consisted of Teflon AF2400 plasticized with a linear perfluoropolyether and doped with ionic sites and a H+ ionophore (i. e., tris[3-(perfluorooctyl)propyl]amine, 1, or tris[3-(perfluorooctyl)pentyl]amine, 2). To mimic a typical CIP treatment, the electrodes were repeatedly exposed for 30 min to a 3.0 % NaOH solution at 90 °C (pH 12.7). ISE membranes doped with the less strongly H+ binding ionophore 1 started to show reduced potentiometric response slopes and increased resistances after one exposure for 30 min to hot 3.0 % NaOH solution. No decomposition of the ionic sites and ionophore 1 at 90 °C was evident by 1H NMR spectroscopy, suggesting that the performance of membranes doped with 1 was compromised primarily by leaching of the negatively charged ionic sites along with H+ into the hot caustic solution. In contrast, even after ten exposures to hot 3.0 % NaOH for a cumulative 5 h at 90 °C, the fluorous sensing membranes doped with the more strongly H+ binding ionophore 2 still showed the ability to respond with a theoretical (Nernstian) slope up to pH 12. Addition of the fluorophilic electrolyte salt methyltris[3-(perfluorooctyl)propyl]ammonium tetrakis[3, 5-bis(perfluorohexyl)phenyl]borate reduced the membrane resistance by an order of magnitude.

Original languageEnglish
Pages (from-to)611-618
Number of pages8
JournalElectroanalysis
Volume30
Issue number4
DOIs
Publication statusPublished - Apr 1 2018

Fingerprint

Ionophores
Cleaning
Membranes
Electrodes
Amines
Caustics
Borates
Polytetrafluoroethylene
Ammonium Compounds
Polytetrafluoroethylenes
Electrolytes
Nuclear magnetic resonance spectroscopy
Leaching
Salts
Decomposition

Keywords

  • cleaning in place
  • fluorous
  • ion-selective electrode
  • ionophore
  • pH
  • Teflon AF

ASJC Scopus subject areas

  • Analytical Chemistry
  • Electrochemistry

Cite this

Cleaning of pH Selective Electrodes with Ionophore-doped Fluorous Membranes in NaOH Solution at 90 °C. / Lugert-Thom, Elizabeth C.; Gladysz, John A.; Rábai, J.; Bühlmann, Philippe.

In: Electroanalysis, Vol. 30, No. 4, 01.04.2018, p. 611-618.

Research output: Contribution to journalArticle

Lugert-Thom, Elizabeth C. ; Gladysz, John A. ; Rábai, J. ; Bühlmann, Philippe. / Cleaning of pH Selective Electrodes with Ionophore-doped Fluorous Membranes in NaOH Solution at 90 °C. In: Electroanalysis. 2018 ; Vol. 30, No. 4. pp. 611-618.
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