Light-emitting-diode-induced fluorescence detector for capillary electrophoresis using optical fiber with spherical end

A simple fluorescence detector for capillary electrophoresis (CE) using a blue light-emitting-diode (LED) as excitation source is constructed and evaluated. An optical fiber was used to collect the fluorescence, and a flat end of the fiber was modified to spherical end, resulting in 50% increase of efficiency over the flat end. A simple device for optical alignment of the fibers and capillary column was designed. The concentration and mass detection limits for fluorescein were 1.8×10−7 mol l−1 and 4.3 femol, respectively.