Microchip-Based Analysis Systems

A new laboratory experiment for instrumental analysis that involves microchip-based analysis systems is described. Students are provided a lithographically-defined master and use it to fabricate a poly(dimethylsiloxane)-based microchip. The flow channel is reversibly sealed over a micromolded carbon electrode and a flow-based amperometric analysis is performed on catechol, a model compound for catecholamine neurotransmitters. The external components of the flow system include a four-port injection valve, a syringe pump, associated tubing, and a computer-controlled potentiostat. The device is evaluated for linearity, limits of detection, calibration sensitivity, and analytical sensitivity. In addition, the effect of flow rate on the amount of peak dispersion in the device is investigated. Instead of the “black box” nature of many current chromatography and flow-analysis systems, the students fabricate a flow-analysis system from raw materials and assemble all of the components of the system. The general approach that is described can be used for different analytes and detection systems and will be of interest to instructors who would like to introduce miniaturized instrumentation, microfluidic principles, and/or flow-based analysis in their courses.