Color reaction of 2,4-dichloro-6-bromo fluorophosphonazo with rare earths and its applicaiton

The coloring reactions of chromogenic reagent 2,4-dichloro-6-bromo fluorophosphonazo(fluorophosphonazo-DCB) with rare earth elements under microwave catalysis were been studied.In the nitric acid medium containing a little pyridine,the chromogenic reagent reacted with rare earth elements to form stable blue complexes after heating catalysis in microwave water-bath at 40℃ for 8 minutes.The molar ratios of lanthanum and cerium to reagent were both 1∶3.The maximum absorption wavelengths of rare earth complexes were in range of 632-636 nm.The apparent molar absorptivities(e) were close and in range of 0.89-1.15×105 L·mol-1·cm-1.The proportion of mixed rare earths was tested at measuring wavelength of 634 nm.The results showed that,the proportion of La,Ce and Y had little influence on the determination of total rare earth elements.The proposed method was applied to the determination of total rare earth elements in actual samples such as rock,with the relative standard deviations(RSD,n=5) of 2.0%-2.4%,and the recoveries of 93%-98%.