Real-time Fluorescence Imaging of Capillary Electrophoresis

An arrangement for real-time fluorescence imaging of capillary electrophoretic separations is described. A decoated capillary was excited along a substantial part of its length by a dye laser pumped with an XeCl excimer laser tuned to match the fluorophors in the sample. Light emitted from the migrating, fluorescent molecules was detected by an image-intensified, thermoelectrically cooled charge-coupled device camera. The camera signals were processed by a computer and displayed as moving peaks on a screen in real-time, thus allowing the progress of the separation to be monitored continuously. Basic characteristics of the imaging arrangement such as sensitivity (signal-to-noise ratio) and resolution were checked with fluorescein samples. The imaging principle was also illustrated with a separation of a mixture of DNA fragments on a commercially available capillary designated for DNA separations. The benefits of real-time imaging for separation processes, in particular for capillary electrophoresis, are discussed.