High-throughput microfluidic devices for NO assay based on electrophoretic separation

In order to develop a high-throughput screening system for NO metabolites (nitrite and nitrate) in biological fluids, we investigated microfluidic devices that use electrophoresis as the basis for separation. Because of the high ionic strength of biological fluids, we first developed a novel running buffer for electrophoretic separation. We also developed a novel way of operating the microfluidic device whereby an apparent separation channel, longer than the actual channel, was formed by controlling the electroosmotic flow (EOF) to obtain complete peak separation. With this new method, high speed separation of nitrite and nitrate was achieved in 15 s. The method was applied to human saliva. We successfully demonstrated complete separation of nitrite and nitrate in 10-fold diluted saliva.