COATED-WIRE ELECTRODES CONTAINING POLYMER IMMOBILIZED IONOPHORES BLENDED WITH POLY(VINYL CHLORIDE)

Polymers containing covalently attached 18-crown-6 or 2.2.2 cryptand u nits were incorporated into plasticized PVC membranes and the composit e membranes were examined as potassium ion sensor elements. Ionosphore s were linked to carboxy-PVC and to poly(acrylic acid) via amide linka ges to an alkyl spacer unit. Coated-wire electrodes (CWEs) from the im mobilized ionosphores gave acceptable responses, but conventional ion- selective membrane electrodes (ISEs) prepared by solvent casting were inactive. Dip-cast membranes did give active ISEs. Potassium electrode performance was independent of the loading of the ionophore within th e acrylate support polymer, but depended upon the spacer length. Ion s electivity varied with the ionophore loading within the support polyme r. Selectivity is a composite of the ionophore selectivity and ion-exc hange interactions with the acrylate backbone, giving selectivities ak in to carboxylate substituted crown ethers, notably enhanced monovalen t/divalent ion discrimination relative to the ionophore in solution. P olymer immobilization extended the lifetime of active electrodes.