Development of a Reflected Light Fluorescence Unit for the Microfluidic Detection System

We have developed a reflected light fluorescence unit for a microchip detection system. This fluorescence detection unit can be attached to a commercial fluorescence photometer. The unit’s equipment includes optical fibers ( # 0.8 mm), a stage that moves 10 mm in the X, Y and Z directions and a special lid for inserting capirally. The excitation light is irradiated on the bottom of the microchip from a close position through the fibers, and the emission is condensed with a lens and then detected by a photomultiplier tube. We have also examined the fluorometric determination of sulfite with N-(9acridinyl)maleimide using this unit and a PDMS microchip. The detection limit of sulfite was 500 j.tM at the microchip. In a comparison of the absolute quantity in the detection volume, the microchip using our unit was better than the conventional cuvette (2.3 nmol and 156 nmol, respectively). It is considered that the fluorescence unit is an effective tool for biological analysis.