CONTINUOUS SAMPLE PRETREATMENT USING A FREE-FLOW ELECTROPHORESIS DEVICE INTEGRATED ONTO A SILICON CHIP

A novel concept for continuous sample pretreatment is presented. A planar silicon structure containing the channel system for free-flow electrophoresis has been fabricated using micromachining techniques. A separation bed (25 mu L volume), two arrays of 125 inlet and outlet channels, and two arrays of 2500 channels used to isolate the separation bed from the electrodes were integrated onto a silicon chip. Free-flow electrophoresis allows the separation of a mixture according to charge with the subsequent continuous collection of the sample band of interest. A continuous separation of rhodamine-B isothiocyanate labeled amino acids over a period of 20 min with an applied voltage of 50 V demonstrates the utility of this technique. The effect of flow from the side channel arrays, sample dilution, and the resolution as a function of the applied voltage is also presented.