Abstract: An iodide-doped, polythienylene coated electrode suitable for a potentiometric iodide ion sensor and a method for its manufacture are disclosed. The electrode is prepared by polymerizing the polythienylene on a working surface thereof. To this end, the working surface is contacted with a monomer solution of thiophene monomer and an electrolyte dissolved in organic solvent. Thereafter the solution is subjected to either a substantially constant potential of about 1.6 volts to about 1.8 volts vs. Ag/AgCl or to a cycling potential between -0.1 volts and +1.8 volts vs. Ag/AgCl for a time period sufficient to polymerize a polythienylene film of the desired thickness onto the working surface of the electrode.The polythienylene film on the working surface is then doped with I.sub.2 by placing the coated electrode in an aqueous solution of iodide salt under applied potential conditions of about +0.6 volts to about +1 volt vs. Ag/AgCl for a period of time sufficient to dope the polymer.

Abstract: A thin layer electrolytic cell is disclosed in which the solution being studied is retained around the working electrode and separated from the electrolyte by an annular piece of a current conducting membrane. The membrane is preferably an ion selective membrane, preferably Nafion, a copolymer of tetrafluoroethylene and a vinylsulfonyl fluoride.