Micromachined separation chips with a precolumn reactor and end-column electrochemical detector

Glass microchips, integrating chemical derivatization reactions, electropho retic separations, and amperometric detection, have been developed. The per formance of the new integrated microfabricated devices is demonstrated for rapid on-chip measurements of amino acids utilizing precolumn reactions of amino acids with o-phthaldialdehyde/2-mercaptoethanol to generate electroac tive derivatives that are separated electrophoretically and detected at the end-column electrochemical detector. The influence of the sample/reagent m ixing ratio, reagent concentrations, driving voltage, detection potential, and other variables is explored. The integrated microsystem offers a rapid (6 min) simultaneous measurements of eight amino acids, down to similar to2 .5 x 10(-6) M (5 fmol) level, with linearity up to the 2 x 10(-4) M level e xamined, and good reproducibility (RSD = 2.2-2.756), A step of the driving voltage is used for decreasing the migration time of late-eluting component s and reducing the overall analysis time. The integrated microfabricated de vice expands the scope of on-chip electrochemical detection to nonelectro-a ctive analytes and holds promise of being a powerful analytical tool.