Measurement of sodium ion concentration in undiluted urine with cation-selective polymeric membrane electrodes after the removal of interfering compounds

Feyisayo Phillips, Kim Kaczor, Neel Gandhi, Bradford D. Pendley, Robert K. Danish, Michael R. Neuman, Blanka Tóth, Viola Horváth, Ernö Lindner

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26 Citations (Scopus)


The measurement of sodium ion concentration in urine can provide diagnostic information and guide therapy. Unfortunately, neutral-carrier-based ion-selective electrodes show a large positive drift and loss in selectivity in undiluted urine. The extraction of electrically neutral lipids from the urine into the sensing membrane was suggested as the main source of the drift, loss of selectivity and the consequent incorrect concentration readings. In this work, (i) solvent-solvent extraction, (ii) membrane-immobilized solvent extraction and (iii) solid phase extraction were used to remove interfering compounds from urine samples. The "cleaned" urine samples were subsequently analyzed using a calixarene (sodium ionophore X)-based, solid-contact, sodium-selective electrode in a flow-through manifold. The solid-contact sodium sensors had excellent stability in cleaned urine and an acceptable bias compared to commercial clinical analyzers.

Original languageEnglish
Pages (from-to)255-264
Number of pages10
Issue number2
Publication statusPublished - Nov 30 2007



  • Ionophore-based electrode
  • Sodium ion monitoring
  • Solid-contact ion-selective electrode
  • Solvent-solvent and solid phase extraction
  • Undiluted urine

ASJC Scopus subject areas

  • Analytical Chemistry

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