Integration of "on-chip" electrochemical detection in a microfabricated capillary electrophoresis device

Our efforts have been focused on developing a self-contained and transportable capillary electrophoresis (CE) system with integrated electrochemical detection (ECD). The current prototype includes all necessary electrodes "on-chip" and utilizes miniaturized CE and ECD supporting electronics custom designed for this purpose. A novel microfabrication procedure was used to create recessed platinum electrodes and the CE/EC device from two patterned ultra-flat glass substrates. The electrodes in the bottom substrate were formed by a self-aligned etch and deposition technique followed by a photolithographic lift-off process. The microchannels (20 μm deep×50 μm wide [avg]) were chemically etched into the top substrate followed by thermal bonding to complete the microchip device. CE/EC experiments were performed using 0.02M phosphate buffer (pH 6), an analyte/buffer solution (2.2 mM dopamine, 2.3 mM catechol) and varying separation voltages (0-250 V) with a custom electronics unit interfaced to a laptop computer for data acquisition. Detection limits (S/N=3) were found to be 4.3 μM for dopamine and 4.4 μM for catechol. A linear detection response was observed up to 2200 μM and 2300 μM for dopamine and catechol, respectively.