Electrochemical detection in capillary electrophoresis with dual-parallel on-capillary electrodes.

A new approach for dual electrode electrochemical detection in capillary electrophoresis (CEEC) is described. In this approach, two identical capillaries, each containing an on-capillary electrode incorporated permanently onto its tip, were paired together for simultaneous sample injection and detection. This procedure permitted dual-parallel detection to be performed without the need for painstaking alignment of the electrodes with respect to one another and to the capillary outlet as is required for the off-capillary microelectrode systems usually employed in CEEC. As a result, independent detection at two electrodes held at different potentials or at two electrodes of different composition or structure could be performed simply and with wide flexibility. Fabrication of on-capillary electrodes was carried out by sputter-coating the exit end of the capillaries with a thin layer of Au or Pt. Dual electrode system performance was demonstrated by separation and analysis of phenol and catechol samples. In addition, the detection system was coupled with glucose oxidase for the selective detection of glucose.