Study on the dual-wavelength spectrophotometry for the determination of rare earth elements with dibromocarboxyarsenazo

The chromogenic reagent dibromocarboxyarsenazo(abb. DBCAA) reacts immediately with rare earths of cerium sub-group to form blue complexes in HCl medium of wide concentration range,and the apparent molar absorptivity of the complex for the dual-wavelength spectrophotometry is(La～Eu)e=1.54×10 5-1.75×10 5 at 636nm. The dual-wavelength spectrophotometry is more sensitive than single-wavelength spectrophotometry.Beer's law is obeyed in the concentration range of 0-20 μg/25 mL for total rare earths. The method has simplicity,high sensitivity,better selectivity and accuracy. The recovery of the method is in the range of 94.3%-104%. It is used directly to determine REs of cerium sub-group in iron base samples and milk powder without separation and concentration.