Micromachined Separation Chips with a Precolumn Reactor and End-Column Electrochemical Detector

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Abstract
Glass microchips, integrating chemical derivatization reactions, electrophoretic separations, and amperometric detection, have been developed. The performance 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 electroactive derivatives that are separated electrophoretically and detected at the end-column electrochemical detector. The influence of the sample/reagent mixing 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 ∼2.5 × 10-6 M (5 fmol) level, with linearity up to the 2 × 10-4 M level examined, and good reproducibility (RSD = 2.2−2.7%). A step of the driving voltage is used for decreasing the migration time of late-eluting components and reducing the overall analysis time. The integrated microfabricated device expands the scope of on-chip electrochemical detection to nonelectroactive analytes and holds promise of being a powerful analytical tool.