Anal. Chem., 74(9), (2002), 1952-1961 Electrophoretic Injection within Microdevices Electrophoresis using Ultra-High Voltages Maribel Vazquez1, Gareth McKinley2, Luba Mitnik3, Samantha Desmarais3, Paul Matsudaira3, Daniel Ehrlich3 1) New York Center for Biomedical Engineering, Department of Mechanical Engineering, The City College of the City University of New York, 140th and Convent Ave T- 250, New York, NY 10031, USA 2) Department of Mechanical Engineering , Massachusetts Institute of Technology , 77 Massachusetts Ave, 3- 250, Cambridge, MA 02139, USA 3) Whitehead Institute for Biomedical Research, 9 Cambridge Center, WI- 339, Cambridge, MA 02142,USA Abstract The flexibility of the microfabricated format creates unique opportunities for study of the electrophoretic process. The present work utilizes digital images to capture the motion of DNA samples during pre-electrophoretic processes. A systematic study of DNA loading and strong sample stacking (sample concentration effects) was performed in order to analyze realistic DNA analysis conditions within microdevices. Using digital imaging and microscopy, DNA sample profiles within the injector were analyzed by deconvolving the geometrical intensity profile into different velocity groups. This analysis illustrates the evolution of molecular separation into distinct migrating populations within the injector itself. The present study performed DNA injections within microfabricated devices imposing run voltages between 85 and 850 V/cm. Data from 3 different offset lengths of a double-T cross-injector, 10 different applied voltages, and 2 different sample preparation protocols are presented.