Cyclic Chronopotentiometry as a Detection Tool for Flowing Solution Systems

Cyclic chronopotentiometry provides a very simple detection method, which may be particularly useful in capillary electrophoresis (CE) and microseparation systems. It has been shown that for disk microelectrodes it is possible to define safe reduction and oxidation currents that would never lead to the formation of H2 or O2 gas bubbles, even if they are applied for an indefinitely long time period. During end-column CE detection, currents passing through the working microelectrode can be completely controlled by the external electronic circuit and they are not affected by the separation current. Consequently, problems created by the offset potential in CE can be completely eliminated. The detection can be accomplished through a variety of different mechanisms; however, generation of the electrode response as a result of analyte adsorption seems to be most common. The method is applicable to many analytes, which do not have to be electroactive. The analytical signal is obtained by monitoring the change in the average electrode potential (calculated for either a cathodic or an anodic half-cycle) caused by an analyte interacting with the electrode. The analytical signal is proportional to the analyte concentration, within a concentration range extending over ∼2 orders of magnitude.