PRECOLUMN REACTIONS WITH ELECTROPHORETIC ANALYSIS INTEGRATED ON A MICROCHIP

A glass microchip was constructed to perform chemical reactions and ca pillary electrophoresis sequentially. The channel manifold on the glas s substrate was fabricated using standard photolithographic, etching, and deposition techniques. The microchip has a reaction chamber with a 1 nL reaction volume and a separation column with a 15.4 mm separatio n length. Electrical control of the buffer, analyte, and reagent strea ms made possible the precise manipulation of the fluids within the cha nnel manifold. The microchip was operated under a continuous reaction mode with gated injections to introduce the reaction product onto the separation column with high reproducibility (<1.8% rsd in peak area). The reaction and separation performances were evaluated by reacting am ino acids with o-phthaldialdehyde to generate a fluorescent product wh ich was detected by laser-induced fluorescence. Control of the reactio n and separation conditions was sufficient to measure reaction kinetic s and variation of detection limits with reaction time. Half-times of reaction of 5.1 and 6.2 s and detection limits of 0.55 and 0.83 fmol w ere measured for arginine and glycine, respectively.