A photometric detector based on a blue light-emitting diode

The suitability of blue light-emitting diodes as radiation sources in molecular absorption spectroscopy was evaluated. Electronic as well as spectral considerations are discussed. A transducer based on a blue light-emitting diode and a photodiode is described which yields direct absorbance readings by passing the photocurrent to an integrated circuit logarithmic converter. The performance of this device was tested for commonly used spectrophotometric procedures for Cr, Mn, Zn, Fe and Cl and compared with conventional molecular absorption spectroscopy. Also investigated was the application of the transducer as a detector in flow-injection analysis.