ELIMINATION OF THE ACETATE INTERFERENCE IN POTASSIUM-SELECTIVE VALINOMYCIN-PVC-MEMBRANES FOR PROCESS-CONTROLLING DURING HEMODIALYSIS

Valinomycin-PVC-membranes of potassium-selective electrodes, which wer e used up to now, show for process controlling during haemodialysis in the presence of dialytic solutions including acetate, an anion interf erence which has to be corrected. On the basis of experimental examina tions on the influence of plasticizers, lipophilic anions and differen t concentrations of ionophoric transport-antibiotics on the nature of membranes, an optimized application could be realized. But surprisingl y, the incorporation of lipophilic anions like tetrakis(4-chlorophenyl )borate induces a significant acetate anion interference. Otherwise, w hen avoiding this lipophilic anion in PVC-membranes with a saturation of valinomycin on oxygen-independent solid-state contact sensors, an e limination of acetate anion interference is achieved if bis(2-ethylhex yl)sebacate is used as plasticizer.