MEMBRANES FOR CHEMICAL SENSORS SELECTIVE TO DOUBLY-CHARGED ANIONS

The main results concerning selective properties fur carbonate sulfate and phosphate polyvinyl chloride (PVC) membranes based on neutral car riers and anion-exchangers are discussed. It is shown that for the inv estigated systems selectivity depends on the concentration ratio betwe en anion-exchanger and neutral carrier. The shape of the curves (selec tivity.vs. neutral carrier concentration) corresponds to a mathematica l model described earlier and determines the stoichiometry of the comp lexes of the anions with neutral carrier. The incorporation of anionic sites inside the anion-selective membrane, e.g., carbonate-selective. leads to an increase of carbonate selectivity in presence of lipophil ic anions of the internal solution.