IMAGING OF HYDRODYNAMIC AND ELECTROKINETIC FLOW PROFILES IN CAPILLARIES

An imaging system based on microscope optics and a charge-coupled device camera is used to form high-resolution images of the liquid core inside narrow fused-silica capillaries. This technique allows direct examination of the fluid motion inside the capillary under electrokinetic and hydrodynamic (Poiseuille) conditions. Two experiments are described. The first involves monitoring the front of the fluorescence-labeled solvent as it travels through the capillary. The second is an examination of the local velocities using submicron-sized particles as probes. The results are discussed in context of band broadening in capillary electrophoresis.