SINGLE PIECE ALL-SOLID-STATE ION-SELECTIVE ELECTRODE

A novel concept of a single-piece all-solid-state ion-selective electr ode (SPE) is introduced. A processable conjugated (electronically cond ucting or semiconducting) polymer (CP) is dissolved in a cocktail cont aining the components used for a conventional ion-selective poly(vinyl chloride) matrix membrane. The cocktail, containing the CP, is cast d irectly on a solid substrate (glassy carbon), resulting in a SPE. The role of the CP is to mediate the charge transfer between the substrate and the membrane. Two soluble CPs are studied: (i) poly(3-octylthioph ene) in its undoped state and (ii) polyaniline doped (protonated) with bis(2-ethylhexyl) hydrogen phosphate. Experimental results obtained f or lithium-selective SPEs and calcium-selective SPEs are discussed. Al l the SPEs studied show near-Nernstian responses, and no redox interfe rence is observed as long as the concentration of the CP is sufficient ly low. The incorporation of a CP, particularly polyaniline, in the me mbrane is shown to improve the stability of the standard potential of the SPE compared to the corresponding coated-wire electrode (membrane without CP). Impedance measurements provide information about the char ge transfer processes of the electrodes.