In-channel simplified decoupler with renewable electrochemical detection for microchip capillary electrophoresis.

Electrochemical (EC) detection is comparable to fluorescence detection in that it is simple to perform, economical, and highly sensitive. In this study, we used replica molding to fabricate a PDMS microchip for microchip capillary electrophoresis (CE). A decoupler electrode and a working electrode were implanted into the PDMS chip during the molding process to prevent leakage into the electrode channel. The working electrode could be renewed readily through its slight withdrawal (ca. 3 mm) from the PDMS; its detection ability was highly reproducible in the microchip CE-EC system. The relative standard deviation (R.S.D.) of the detecting current for the renewed working electrode was 1.2% (n=5). The calibration curves were linear for both dopamine and catechol analytes over the concentration range 10-1000 microM, with coefficients of determination (R(2)) of 0.999 and 0.976, respectively. The number of theoretical plates (N/m) for these analytes was greater than 133,000.