Carbon Film-Based Interdigitated Array Microelectrode Used in Capillary Electrophoresis with Electrochemical Detection

Abstract

A carbon film based interdigitated ring-shaped array (IDRA) microelectrode was applied to capillary electrophoresis with electrochemical detection to enhance the detection sensitivity on the basis of the redox cycling of electrochemical reversible species at the IDRA microelectrode. We propose a simple capillary-electrode connection device that consists of an X-Y-Z fiber aligner, an electrochemical cell, and a Nafion tubing joint that will enable the detection capillary to be aligned easily on the IDRA microelectrode and isolate the separation voltage from the electrochemical detection system. We used the off-column amperometric detection of aqueous ferrocene and catecholamines by capillary electrophoresis with an IDRA microelectrode to investigate the effects of the capillary-to-electrode distance and the separation voltage on the response currents in single and dual modes and the collection efficiencies (CE) and redox cycles (Rc) at the IDRA microelectrode. The results show that CE and Rc increase when we increase the distance and lower the separation voltage. The limiting currents also increase as the separation voltage decreases in the dual mode. Under optimum conditions, the CE and Rc of catechol, with good reversibility, reach 83.9% and 3.67, respectively. Our results showed that dual-mode detection with the IDRA microelectrode was capable of achieving lower detection limits than single-mode detection.