Microchip separation and electrochemical detection of amino acids and peptides following precolumn derivatization with naphthalene-2,3-dicarboxyaldehyde

An integrated microfluidic device is used to derivatize, separate, and amperometrically detect amino acids and peptides in the presence of naphthalene-2,3-dicarboxyaldehyde (NDA). The integrated system offers a rapid (4 min) simultaneous measurements of 5 amino acids (Arg, Lys, Gly, Cys, PhenA) down to the 3.2 μM level in connection to a precolumn reaction chamber, an electrophoretic separation channel, and an end-column thick-film carbon-electrode detector. The effect of the separation voltage, detection potential, reagent concentration, and other variables on the response is examined. Calibration and precision experiments indicate a linear and reproducible response. Applicability for the separation and detection of small peptides is demonstrated. Such on-chip generation of electroactive products offers great promise for detecting other nonelectroactive analytes.