A Microchip Electrophoresis Device Integrated with the Top-bottom Antiparallel Electrodes of Indium Tin Oxide to Detect Inorganic Ions by Contact Conductivity.

A microchip electrophoresis (ME) device with off-channel contact conductivity detection (C2D) was constructed using top-bottom antiparallel indium tin oxide (ITO) electrodes and a cross-type microchannel. The 500-m wide top-bottom antiparallel decouplers were found to effectively decrease the interference of the electrophoretic current. The cross-type microchannel was formed by bonding the patterned negative photoresist microstructures and the two top-bottom opposed ITO-deposited glass substrates. Five seconds of 150 V/cm injection field and the 100 V/cm separation field equipped with the C2D of AC 200 mV excitation voltage provided adequate ME operational parameters to obtain the K+ and Na+ peaks separation. The ME devices obtained good coefficients in a range of 11000 µM for the K+ and Na+ detection. The calculated limit of detection was 1 µM. This design for off-channel and top-bottom antiparallel electrodes shows that C2D ME devices have great potential for the measurement of inorganic ions.