- Technical Field: The present invention relates to electrochemical devices and methods for quantitative or qualitative analyses of a substance in the presence of an enzyme, particularly an oxidase enzyme. Exemplary oxidases are glucose oxidase, lactate oxidase and others, such as those below; and the invention more particularly relates to measuring the glucose, lactate, etc. in the material to be analyzed.Cross-Reference to related to U.S. Patents Application: Reference is made to copending, commonly assigned, U.S. patent application Ser. No. 407,566, filed August 12, 1982, for "Apparatus and Method for Electrochemical Measurements", the entire disclosure of which hereby is incorporated by reference.Background: Reference also is made to U.S. Pat. Nos. 3,539,455 and 4,340,448, the entire disclosures of which hereby are incorporated by reference. Such patents disclose approaches to measuring certain materials in the presence of specified enzymes of such materials, for example glucose in the presence of glucose oxidase, etc.U.S. Pat. No. 3,539,455 discloses a technique for measuring the concentration of glucose by allowing the glucose to diffuse through a membrane into an electrolyte that contains an enzyme, particularly an oxidase, such as glucose oxidase. In the electrolyte a reaction occurs to produce hydrogen peroxide. The electrical current produced during that reaction is measured as a representation of the glucose concentration. When there is interfering material in the unknown sample, which also contains the glucose means are provided by the patentee to subtract the current produced by the intefering material from the current produced by the interfering material and that material whose concentration is to be measured. The device of the U.S. Pat. No. 3,539,455 suffers from inaccuracy and instability due to the relatively low signal strength and, as the patentee recognizes, the difficulty in maintaining a uniform oxidase layer at the membrane. In U.S. Pat. No. 4,340,448 the need for an electrolyte separate from the unknown material, separated therefrom by a selective diffusing membrane, is overcome by immobilizing the enzyme directly on the cathode (working electrode) of the sensor system. The cathode and reference electrode both are inserted into an electrolyte that contains the unknown concentration of material intended for measurement. Such immobilization is achieved by confining the enzyme in a gel that is applied to the working electrode; the gel permits oxygen and glucose to diffuse therethrough. In the above mentioned application Ser. No. 407,566, there is disclosed an apparatus and method for making electrochemical measurements of certain species, especially of the type that undergo oxidation and/or reduction reactions.