Polarographic detector:

A polarographic detector consists of a mechanically controlled dropping mercury electrode where eluent flows around the mercury droplet. The potential of the electrode is then maintained at a suitable level during elution. Plot of current vs time provides elution pattern for species that are reduced at the chosen potential.

A dual electrode detector offers additional specificity. In one configuration, two working electrodes are placed parallel with the flowing stream where each electrode is held at a different potential, thus, generating two simultaneous chromatograms. The current ratio at the two potential settings is calculated and used for peak confirmation. The second configuration has two electrodes arranged in series. The upstream working electrode generates an electroactive product from the analyte which is subsequently detected at the downstream working electrode. The series of arrangement limits the number of electroactive compounds that are detected. Only the compounds that generate stable electroactive product and reach the second electrode are sensed.