Direct Potentiometric Measurement of Potassium in Blood Serum with Liquid Ion-Exchange Electrode

Abstract

A new liquid ion-exchange electrode is described which has a selectivity for K⁺ over Na⁺ of 93:1 in 0.1 mol/kg solutions. Its response is Nernstian in the range 5 x 10^-4 to 5 x 10^-1 mol KCl per kg. The dip-type electrode responds to small changes in K⁺ in mixed salt solutions containing the same quantities of KCl and NaCl as human blood serum. A miniaturized form of the electrode was adapted to a capillary flow-through system for blood sera. It gives results for K⁺ in the normal range that agree with flame photometric values without correction for Na⁺ in the concentrations normally present. The effect of pH on the K⁺ response and the response of the electrode to Mg⁺⁺, Ca⁺⁺, NH₄⁺, Rb⁺, and Cs⁺ are also illustrated.