A gradient elution method with conventional electrochemical detection was developed to separate four analogs of the nitroxide 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) free radical in less than 3 min. The corresponding hydroxylamines and oxoammonium ions of these free radicals were separated using the identical chromatographic method. A dual microelectrochemical detector was constructed that allowed for simultaneous anodic and cathodic detection of all three redox forms. This detector was superior to a conventional electrochemical detector because it could provide immediate information about the oxidation state of the nitroxide, it nearly eliminated post-column band broadening, and it was less susceptible to changes in oxygen concentration of the mobile phase during gradient elutions.