A technique for investigating mixtures of charged species. In capillary zone electrophoresis (CZE), the sample is introduced into a fine capillary tube, with each end of the capillary placed in a reservoir containing an electrolyte (e.g. a buffer solution). The source reservoir contains a positive electrode and the destination reservoir contains a negative electrode. A high potential difference is maintained between the electrodes. Components of the sample flow through the buffer solution in the capillary under the influence of the electric field. Their mobility depends on their charge, size, and shape, and the components separate as they move through the tube. They are detected close to the end of the capillary, usually by ultraviolet absorption. Capillary gel electrophoresis (CGE) is used for separating large charged species, such as DNA fragments. The capillary is filled with a gel and separation depends on the size of the species. In CE, a graph of detector output against time is known as an electropherogram. Individual components can be identified by their retention times in the capillary. The technique can be highly sensitive and is widely used in forensic laboratories.