A two-electrode system-based electrochemiluminescence detection for microfluidic capillary electrophoresis and its...

A two-electrode configuration powered by batteries was designed for a microchip capillary electrophoresis-electrochemiluminescence system. A home-made working electrode for end-column mode detection and wall-jet configuration was made up of a platinum wire (0.3 mm diameter) and a quartz capillary (320 µm internal diameter). The platinum wire served as a pseudoreference electrode. The configuration of the detection power supply comprised two D-size batteries (connected in series), a switch, and an adjustable resistor. The microchip consisted of two layers: the bottom layer was a glass sheet containing injection and separation channels; the upper layer was polydimethylsiloxane block. In order to reduce the loss of electrochemiluminescence signal, a coverslip (0.17 mm thickness) was used as the floor of the detection reservoir. The performance of the system was demonstrated by separation and detection of atropine, anisodamine and proline. The linear response for proline ranged from 5 µM to 100 µM (r = 0.9968), and the limit of detection was 1.0 µM (S/N = 3). The system was further applied to the measurement of atropine in atropine sulfate injection solutions with the limit of detection 2.3 µM. This new system is a potential tool in pharmaceutical analysis.