Electrochemical detection cell

Claim 1

An electrochemical cell for quantitatively detecting a .Iadd.noxious .Iaddend.gas .Iadd.in the presence of air .Iaddend.comprising an anode having catalyst bonded to polytetrafluoroethylene to provide a diffusion electrode, a cathode, a reference electrode .Iadd.at which substantially no current flow.Iaddend., and an aqueous electrolyte .[.in contact with.]. .Iadd.within an electrolyte container, each of said anode, cathode and reference electrode having a catalytic surface contacting .Iaddend.said .[.anode, cathode and reference electrode;.]. .Iadd.electrolyte, and said reference electrode contacting air, .Iaddend.means for exposing said anode to a .[.gaseous substance.]. .Iadd.gas containing a noxious gas .Iaddend.to be detected; .Iadd.said anode being arranged in said cell so that one surface of said anode contacts said gas exposing means and the opposite surface contacts said electrolyte whereby the noxious gas to be detected migrates from the surface contacting said gas exposing means to the internal surface of said anode to interface with the electrolyte for reaction in the presence of the catalyst, .Iaddend.means connecting said anode and reference electrode, said latter means being a potentiostat .[.for.]. maintaining a fixed potential on said anode relative to said reference electrode of from about 0.9 to 1.5 volts with respect to the potential of the reversible hydrogen couple in the electrolyte of said cell which potential is independent of the concentration of the .Iadd.noxious .Iaddend.gas to be detected and means for measuring said current flowing between sad anode and cathode of said cell, said measured current being a measure of the concentration of the gas being detected.