The composition of polymeric membranes, including the amounts of appropriate ionophores, lipophilic salt, plasticizer, and highmolecular-weight PVC as well as respective conditioning solutions are listed in Table . All components were dissolved in 1 mL of tetrahydrofuran in case of the syringe electrodes and 500 µL for the standard ISE electrodes. 0.1M KCl was used as the internal solution.