甲基绿显色分光光度法测定微量铈

Spectrophotometric Determination of Cerium Using Methyl Green as a Chromogenic Reagent

Ce(Ⅳ )的强氧化性对甲基绿有显色作用 ,借此建立了分光光度法测定铈的新方法。实验表明 ,在 0 .2 5～ 0 .63mol/LH2 SO4介质中 ,甲基绿被Ce(Ⅳ )氧化而生成深色化合物 (λmax=465nm) ,且颜色的深度与Ce(Ⅳ )的存在量呈线性关系。Ce(Ⅳ )量在 0～ 4.0mg/L内符合比尔定律 ,表观摩尔吸光系数为 1 .1 6× 1 0 4 L·mol- 1 ·cm- 1 。方法用于测定稀土氧化物中的铈时 ,结果与等离子体发射光谱法一致 ,5次测量结果的RSD <1 .5 %。

Based on the chromogenic reaction of methyl green with Ce(Ⅳ) in H 2 SO 4 (0.25～0.63 mol/L) medium,a new method for the determination of micro amount cerium is developed. The maximum absorption is at 465 nm. Beer′s law is obeyed in a concentration range of 0 to 4.0 mg/L of cerium. The apparent molar absorptivity is 1.16×10 4 L·mol -1 cm -1 . The method has been used for the determination of cerium in rare earth oxides and the results are in agreement with those provided by ICP AES with precision of <1.5% RSD ( n =5).