On-column amperometric detection for capillary electrophoresis microchips with electric field decoupler

In this study, we investigated a micro (micro electromechanical system) technology. The CE-EC chips consisted of a upper layer containing the separation and injection channels formed by poly(dimethylsiloxane) (PDMS) molding and a lower layer fabricated by using photolithography process to deposit Au on glass as the detection electrodes. The surface of PDMS layer was treated with oxygen plasma to improve the bonding strength and the effect of electroosmotic flow (EOF). 50 mM ferrocyanide was performed in CE-EC chips with separation field of 60 V/cm, and the oxidation current detected can reach 105 nA. The result was suggested that EOF indeed exists in oxidized PDMS because the negative charge molecules can be detected in cathode terminal of the separation column. In addition, 10 mM norepinephrine, was carried out with electric field of 60 V/cm to estimate the separation efficiency. The theoretical plate number of norepinephrine calculated from the electropherogram result is 9026889. The result was shown that the EC-CE microchip was suitable for electrochemical detection and have a good separation efficiency.