A portable battery powered electrochemical detection circuit with a 1000 volt CE power supply for microchip capillaries

Capillary electrophoresis (CE) with electrochemical detection (ECD) is an attractive combination for a miniaturized portable instrument. Capillaries and integrated detection electrodes can be fabricated accurately and at low cost using microfabrication processes. Precise sample injection and electrode alignment issues are addressed via interconnecting capillaries and patterned electrodes respectively. However, to fully realize the portability offered by microfabricated devices, a portable battery powered ECD circuit and HV CE power supply is developed. The ECD circuit and HV CE power supply are each constructed on 3"×4" PCBs including batteries. The detection circuit has adjustable gain, applied electrode voltage, and current offset. The CE power supply contains one positive and one negative voltage source. Each voltage source is filtered, regulated, adjustable from 250 VDC to 1 kVDC, and can source up to 400 μA. Both the power supply and detection circuit are connected to a portable computer using LabView software for control and data acquisition. A capillary biasing method using the negative voltage source for injection and the positive voltage source for separation is also presented. This method simplifies detection and capillary current measurement circuits and requires minimal interface circuitry. The CE power supply performance is evaluated with electrical tests and a laser induced fluorescence (LIF) experiment. The detection circuit is tested by performing dopamine and catechol ECD experiments. Results show the successful injection, separation, and electrochemical detection of analytes using microchip capillaries