AbstractA conducting, chemically synthesized, Cu(II)‐containing poly(3‐methylthiophene) powder was pressed into a pellet and used as the working electrode of a three‐electrode system in a thin‐layer amperometric cell unit to detect ionic analytes in an aqueous stream by flow‐injection analysis. The electrode response was linearly correlated with the applied voltage, which was varied between 0.2 and 3.0 V (vs. Ag/AgCI). It was shown that the electrode possesses favorable sensitivity and stability in comparison with other metallic electrodes such as stainless steel and Pt. During a period of more than a year, it showed no deterioration in its pe