Study on determination of total amounts of rare earth by spectrophotometry with 2.6-dibromo-4-fluoro fluorophosphonazo

The colour reactions of the new chromogenic reagent 2.6-dibromo-4-fluoro fluorophosphonazo(fluorophosphonazo-DBF) with rare earth elements(RE) have been studied.In the medium of 0.06 mol/L sulfuric acid,the chromogenic reagent reacts with 15 rare earth elements to form blue complexes,in the presence of emulsifier OP and ethanol.The molar ratio of lanthanum to reagent is 1∶3.The molar absorptivity e of respective rare earth complex is 0.75～1.13×10~5 L·mol~-1·cm~-1.The maximum absorption wavelength lies at 632～635 nm.The mixed RE content obeys Beer′s law in the range of 0～0.60 μg/mL.With the solution of 4 mixed screening agents,the method can be directly applied to the determination of total RE in samples.The recoveries of the method are 93.8%～104.3%.