Determination of the Total Amount of Rare Earth in Green Tea and Rice by the Dual-wavelength Spectrophotometry with Dibromocarboxyarsenazo

Chromogenic reagent dibromocarboxyarsenazo reacts with cerium subgroup rare earths to form blue complexes in an acidic medium of the wide range.the maximum absorption of dibromocarboxyarsenazo and its cerium complex are at 534nm and 636 nm respectively.Beer's law is obeyed in the range of 0~20μg /25mL for total rare earth content with a dual-wavelength spectrophotometry,which is more sensitive than singl-wavelength spectrophotometry,and its molar absorptivity is 1.54×10~5~1.71×10~5.The method has been used to determine the cerium subgroup rare earths in the green tea and rice with satisfactory results and it is precise(RSD6%),sensitive,accurate(recovery rate 89%~105%) and simple.