Abstract: The use of a metallic copper wire electrode for potentiometric detection of organic acid anions in ion-exchange chromatography is described. These anions were detected by changes in electrode potential resulting from complexation of copper(I) or copper(II) ions at the electrode surface. The direction of this potential change, and hence the direction of the peak produced, was found to depend on the relative strengths of copper complexation between the injected ligand and the eluent ligand. Calibration relationships between the electrode potential and the amount of injected solute were studied and were observed to depend on the type of solute and the amounts injected. Several separations obtained using the copper wire electrode detector are presented as examples. Included are separations of glycinate, glutamate, and oxalate, and of acetate, lactate, formate, succinate, and benzoate.