The construction of a simple absorption monitor for capillary electrop
horesis, based on a bright blue-green light emitting diode as radiatio
n source, is described. Fibre optic coupling between light source, cap
illary and photodiode detectors was employed. It was found that, owing
to the use of a high intensity light emitting diode, no optical focus
ing elements were required. The performance of the device was found to
be comparable to that of a commercial detector, and the versatility i
s demonstrated with methods for the determination of transition metal
ions by complexation with 4-(2-pyridylazo)resorcinol and the indirect
detection of other inorganic cations and anions using organic dyes.