Three-electrode electrochemical detector and platinum film decoupler integrated with a capillary electrophoresis microchip for amperometric detection

This article demonstrates that a three-electrode electrochemical (EC) detector and an electric decoupler could be fabricated in the same glass chip and integrated with an O₂-plasma-treated PDMS layer using microfabrication techniques to form the capillary electrophoresis (CE) microchip. The platinized decoupler could mostly decouple the electrochemical detection circuit from the interference of an separation electric field in 10 mM 2-(N-morpholino)ethanesulfonic acid (MES, pH 6.5) solution. The baseline offset of background current recorded from the working electrode with and without application of a separation electric field was maintained at less than 0.05 pA in 10 mM MES. In addition, the platinized pseudoreference electrode was demonstrated to offer a stable potential in electrochemical detection. As a consequence, the limit of detection of dopamine was 0.125 μM at a S/N = 4. The responses for dopamine to different concentrations were found to be linear between 0.25 and 50 μM with a correlation coefficient of 0.9974 and a sensitivity of 11.76 pA/μM. The totally integrated CE-EC microchip should be able to fulfill the ideal of miniaturization and commercialization.