All-solid-state potassium-selective electrode using double-layer film of polypyrrole/polyanion composite and plasticized poly(vinyl chloride) containing valinomycin

All-solid-state potassium-selective electrodes have been constructed on a Pt disk electrode using a double-layer film of polypyrrole/poly(4-styrenesulfonate) (PPy/PSS) composite covered with a plasticized poly(vinyl chloride) (PVC) membrane containing valinomycin. The lower composite layer is formed by electropolymerization of pyrrole in an aqueous solution containing poly(sodium 4-styrenesulfonate), and the upper PVC layer is formed by casting. The double-layer film electrode using this composite shows no overshoot and lower drift of the standard potential than both a single PVC-coated electrode and a double-layer electrode using polypyrrole doped with ClO₄^-. This is due to both the highly electrochemical activity of the lower PPy/PSS and the cation-exchange ability between the PPy/PSS and the potassium-selective membrane.