The disclosed invention provides methods and instruments for fluorescence
detection making it possible to separate and detect analytes of a
plurality of species in a migration (separation) channel with length of
the order of millimeters. Analyte samples disperse across the whole
detection region of a migration channel filled with a sieving matrix.
Electrodes located in contact with a power supply and the sieving matrix
cause the analytes to electophoretically migrate at predetermined velocity
V. The detection region is irradiated by excitation light whose intensity
changes in a cycle equaling pitch p in the direction that the analytes
move. Fluorescence emission from the analytes exposed to the excitation
light is detected by a detector. Fluctuation .delta.i (t) of output
current from the detector is analyzed by a spectrum analyzer and the
obtained spectrum is displayed. Florescence detection according to the
invention is not affected by band broadening of analytes injected into the
sample injection end of the migration channel.
