钛铁试剂分光光度法直接测定轻稀土中的铈  

Direct Spectrophotometric Determination of Cerium in the Mixture of Rare Earths with Tiron

作　　者：陈玉銮[1] 王济奎[1] 汤旭东 周祝敏[1] 

机构地区：[1]南京化工大学应用化学系

出　　处：《分析测试技术与仪器》1997年第2期107-112,共6页Analysis and Testing Technology and Instruments

摘　　要：利用铈的变价以及Ｃｅ（Ⅳ）－Ｔｉｒｏｎ配合物在不同酸度条件下颜色的特殊性，建立了无需预先分离而直接测定混合稀土中铈含量的分光光度法。在ｐＨ为９．０条件下，借助空气的氧化，Ｃｅ（Ⅲ）和Ｃｅ（Ⅳ）都与Ｔｉｒｏｎ形成Ｃｅ（Ⅳ）－Ｔｉｒｏｎ配合物。该配合物在ｐＨ为５．０时呈亮黄色，在４３５ｎｍ处有最大吸收。铈的浓度在０～８０μｇ范围内，符合Ｂｅｅｒ定律：摩尔吸光系数ε＝１．６４×１０３Ｌ／（ｍｏｌ．ｃｍ－１；检出限为１．８８μｇ／ｍＬ；线性回归方程为Ａ＝０．０１１７Ｃ－０．０１８（Ｃ以μｇ／ｍＬ表示），线性相关系数γ＝０．９９９２。对稀土样品平行测定６次，变异系数ＣＶ≤２．３％。共存的轻稀土离子对铈的测定无干扰。用于稀土氧化物及稀土盐中铈的测定，结果与ＫＭｎＯ４法比较，相对误差≤０．５５％。A direct method is presented about the spectrophotometric determination of cerium, which is based on the reaction of ceric ion with Tiron.. Results shows that cerious ion can not form a color complex with Tiron, but ceric ion in pH 5.0 HAc-NaAc medium reacts slowly with Tiron and gives a stable soluble bright yellow complex with a maximum absorption at 435 nm.In a basic medium, the reaction of ceric ion with Tiron becomes very rapid, but oxygen dissolved in solution can rapidly transfer cerious-Tiron complex to ceric-Tiron complex with wine red. Ceric-Tiron complex in pH 5.0 HAc-NaAc medium can keep a stable bright yellow color for many hours. Beer′s law is obeyed in the range of 0.80μg/mL cerium at 435nm. The apparant molar absorptivity is 1.64×10 3 L/(mol.cm)and the detection limit is 1.88μg/mL. The linear regression equation is A=0.011 7C-0.018,and the linear limit is 1.88μg/mL. The linear regression equation is A=0.011 7c-0.018,and the linear correlatiion coeffcients(r) are found to be better than 0.999 2. The coefficient of variation is lesser 2.3%(n=6). Other light rare earth ions have no interference. The recommended method has been used to determine cerium in the mixture of rare earhts without prenious separation and oxidation of cerium in advance.

关 键 词：铈 钛铁试剂 分光光度法 轻稀土 

分 类 号：O614.332[理学—无机化学]