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

中文关键词:  铈  钛铁试剂  分光光度法  轻稀土  直接测定

英文关键词:cerium  Tiron  spectrophotometry  light rare earth  direct determination

中文摘要:

      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%.

英文摘要:

      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 1.64×10³ 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.