Development of rotating electrochemical detectors for capillary electrophoresis

A rotating disk electrode (RDE) has been evaluated and optimized for the detection of electroactive species separated by capillary electrophoresis (CE). With catechol as a working model, the limit of detection was estimated to be 0.3 microM, i.e., approximately 2.5-fold better than that of the stationary disk electrode (0.7 microM). Separation efficiency was significantly improved as exemplified by an increase of theoretical plates from 26,000 plates/m at 0 rpm to 67,000 plates/m at 500 rpm. Of particular importance was the capability of RDE to alleviate electrode passivation and electrical interference associated with high separation potential fields. Therefore, rotation amperometry was especially useful for analytes such as phenolic compounds that tended to rapidly foul the electrode surface. The RDE/ CE system was capable of separation and determination of pentachlorophenol in contaminated soils, and the result obtained agreed well with conventional liquid chromatography, an EPA recommended procedure.