SIMPLE SYSTEM FOR THE MEASUREMENT OF ION ACTIVITIES WITH SOLVENT POLYMERIC MEMBRANE ELECTRODES

A simple device for the application of ion-selective liquid membrane electrodes to biochemistry is described. K+- and Ca2+-selective membranes were sealed on polyvinyl chloride (PVC) tubing and inserted into the side wall of a Plexiglas reaction vessel, enabling simultaneous measurements of K+ and Ca2+. The vessel also permits the simultaneous detection of changes in pH and oxygen and is predisposed to work under a controlled atmosphere. The system is particularly suitable for the measurement of fast changes in ion activities, since the stirring system described has a mixing time below 0.1 s. The 95% response times of the ion-selective electrodes and of the oxygen electrode were below 0.5 s. The volume of the reaction vessel is 0.5-1.0 ml. © 1979.