Comparison of Four Carbon Fiber Electrodes in Microfluidic Chip Integrated With Electrochemical Detector

A microchip electrophoresis system with integrated amperometric detector was developed. Using 0.02 M Tris-HCl (pH = 8) as buffer, at the detection potential of 0.6 V (vs. Ag/AgCl), dopamine (DA) and isoprenaline (IP) were detected by chip-CE with end-column amperometric detection using a carbon fiber microelectrode (CFME), a carbon fiber nanoelectrode (CFNE), a carbon fiber microelectrode modified by single-walled carbon nanotubes (SWNTs-CFME), and a carbon fiber microdisc electrode (CFMDE). The resolution of DA and IP are 0.64, 1.06, 0.61 and 1.22, and the sensitivity of DA (S/N = 3) are 1.7 × 10−7, 5.9 × 10−8, 2.3 × 10−8, and 5.3 × 10−7, respectively. As the CFNE had high resolution and sensitivity, the nanoelectrode-based microchip CE system was successfully applied to the determination of DA in cultured rat pheochromocytoma (PC12) cells, and the average content of DA in an individual PC12 cell was 0.57 ± 0.07 fmol (n = 5), which was in good agreement with that reported in the literatures.