二溴羧基偶氮胂双峰双波长分光光度法测定稀土元素研究

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

在 1 2mol/LHCl介质中 ,显色剂二溴羧基偶氮胂与稀土元素能发生高灵敏度的显色反应 ,形成稳定的蓝紫色络合物 ,试剂和络合物的最大吸收波长分别位于 5 3 4nm和 63 6nm ,用双峰双波长分光光度法测定痕量稀土总量。结果表明 ,本法有较高灵敏度 ,表观摩尔吸光系数 (La～Eu)达 1 5 4× 10 5～ 1 75× 10 5;在 2 5mL溶液中稀土元素质量在 0～ 2 0 μg范围内符合比尔定律 ;受酸度及共存离子的影响小 ,并具有准确、快速、简便的特点 ;方法回收率达 94 3 %～ 10 4% ,可不经分离富集 ,直接用于实际样品中痕量稀土的测定 。

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)ε=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.