A dual electrochemical detector having two working electrodes (anode and cathode) suitable for micro high-performance liquid chromatography has been characterized for the selective detection of catecholamines on the basis of their electrochemical reversibility. The rapid determination of applied potentials for such electrochemical detectors in liquid chromatography by means of cyclic semi-differential voltammetry is described. The dual electrochemical detector has been successfully utilized for the selective determination of catecholamines in human urine injected directly into a micro high-performance liquid chromatograph with an alumina preconcentration micro-column.