A New Electrochemical Determination of Potassium Ion Concentration with Immobilized Valinomycin Disk

A new electrochemical determination f potassium ion concentration in serum with immobilized valinomycin disk was studied, in which the disk having porous structure was prepared by radiation polymerization f hydrophilic monomer at low temperature. The method was based upon the measurement of he current resulting from liberated potassium ion in the disk. The sensitivity varied with the pore size in the porous polymer matrix of the disk, which depends on monomer concen-tration. Potassium ion concentration ranging from 0.4 to 10 mM/1 can be easily assayed with precision of 2 % by using 20 ~] of sample. The correlation between potassium ion concentrations in sera measured by flame photometry and bythe present, method was good (r = 0.91). l)etermination of sodium and potassium ion concen-tration in blood serum is important in diagnostic assay, so that various methods have been developed (1-3). The average concentration ranges of sodium and po-tassium ion in serum of normal humans are 134-I43,and 3.5-5.4 mM/1, respectively. Thus, the concentration range is very narrow, so that an analysis method wit