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

Abstract

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.