Volume 12, Issue 3-4

This review deals with the spectrophotometric and/or spectrofluorimetric determination of individual rare earth elements in rare earth mixtures by their characteristic absorption or fluorescence of 4f electron transitions, including conditions of maximal absorption or fluorescence, molar absorptivity, ranges of linearity, detection limits, interference, and application of these methods with 136 references cited.

The asymmetric bisazo derivatives of Arsenazo and Phosphonazo have been widely used as chromogenic reagents in spectrophotometric determination of thorium, uranium, rare earth elements and other heavy metals. They exhibit advantages over the symmetric reagents such as Arsenazo m and Chlorophosphonazo III both in sensitivity and selectivity. The following is a brief introduction and short review on these reagents concerning their structures, analytical characteristics, synthesis, purification and application. 182 references mainly published in the past decade are presented.