The limitations of ion-selective electrodes (ISEs) presently in use mainly concern the stability of the calibration values. By applying optimal membrane technologies and optimized reference electrodes a perfectly symmetric measuring system including a symmetric ISE membrane has been developed. Thus, stable standard potentials of the cell assembly, both before and after serum contact, as well as theoretical slopes of the electrode response have been obtained. Results of calibration-free assays of K+ and Na+ concentrations in aqueous calibration solutions and in undiluted human serum are presented. The precision required in fully met for K+ measurements in aqueous solutions and in sera of the normal as well as pathological concentration range. In addition, the precision of Na+ assays in aqueous calibration solutions and in serum samples of the normal concentration range is close to the required values.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.