PHYSICOCHEMICAL PROPERTIES OF A LIQUID ION EXCHANGER MICROELECTRODE AND ITS APPLICATION TO BIOLOGICAL FLUIDS

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Abstract
Double-barreled K+ or Cl- selective microelectrodes were constructed using a liquid ion exchanger. Technical details of the fabrication of double-barreled microelectrodes, having a PD sensor as 1 barrel and an ionic sensor as the other, are described. The sensitivity of K+ or Cl- selective microelectrodes exhibited an approximately Nernstian response over a temperature range of 7-37.degree. C, and the electromotive force (EMF) was stable within .+-. 1 mV for a few hours. The rise time was less than 1 s. The effect of pH on the electrode response was negligible over a physiological range of pH 5.6-7.8. The selectivity constants of the K+ microelectrode to other cations were 0.011 for Na+, 0.200 for .**GRAPHIC**. and < 0.002 and 0.001 for Ca2+ and Mg2+, respectively, while that of the Cl- microelectrode was 0.067 for .**GRAPHIC**. Glucose or urea has no effect on the EMF. Protein has a significant effect on ion exchanger membrane only when the concentration of the tested ion is low and protein is high. On the basis of this background the determination of K+ and Cl- activity was carried out in vivo and in vitro on several biological samples, e.g., serum, tissue and cellular fluids and other protein-containing fluids. The values obtained with the microelectrode were consistent with those obtained with the other conventional methods or with the current theory on electrolyte solutions.

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