Capillary electrophoresis detector using a light emitting diode and optical fibres

The construction of a simple absorption monitor for capillary electrophoresis, based on a bright blue-green light emitting diode as radiation source, is described. Fibre optic coupling between light source, capillary and photodiode detectors was employed. It was found that, owing to the use of a high intensity light emitting diode, no optical focusing elements were required. The performance of the device was found to be comparable to that of a commercial detector, and the versatility is 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.