Optimization of a reference electrode with constrained liquid junction forthe measurements of ions

In direct potentiometry even small changes in the diffusion potential at li quid junction can lead to erroneous results, especially when the analytical potential range is narrow. The method of optimization of composition of a reference electrode to minimize the influence of bridge dilution and sample composition changes is proposed. The method allows one to find the best mi xture of salts to be used as well as their concentration ratios. Pseudo-sol id-state reference bridges with how constrained by Teflon were used in the experiments. The performance of reference electrode equipped with this brid ge was tested against calcium and potassium ISE and the optimization of the bridge was made for serum matrix. For this matrix a mixture of potassium c hloride and sodium bicarbonate was found to be most advantageous.