阻抑动力学法测定铈的新指示反应研究——Ce(Ⅲ)-H_2O_2-水扬基荧光酮体系

A Novel Kinetic Method of the Determinating Cerium(Ⅲ) Based on H_2O_2-Salicyl Fluoronyl Redox Indicator Reactions

在碱性介质中，铈（Ⅲ）能显著地阻抑Ｈ２Ｏ２氧化水扬基荧光酮（ＳＡＦ）褪色的指示反应，研究表明该动力学反应对铈（Ⅲ）为一级，测得反应的表观活化能为２８．７５ｋＪ／ｍｏｌ。据此建立了测定痕量铈的动力学分析法，测定条件为ＳＡＦ：４．０×１０－５ｍｏｌ／ｌ，Ｈ２Ｏ２：０．０１０％，ＮａＯＨ：２．０×１０－２ｍｏｌ／ｌ，５０℃。线性测定范围０．０４μｇ／ｍｌ～０．４４μｇ／ｍｌ，方法检测限为０．０２μｇ／ｍｌ（Ｃｅ）。当溶液中的铈含量为０．１６μｇ／ｍｌ时，３～８倍量的轻稀土，５～１１倍量的重稀土和同倍量的铀和钍等不干扰测定。测定了按不同稀土矿的稀土元素配分合成的样品中的铈含量，结果满意。

The redox reaction between H_2O_2 and salicyl fluoronyl is strongly inhibited by cerium(Ⅲ) in alkline medium. The reaction is first order for Ce(Ⅲ), and the apparent active energy was determined to be 2875 kJ/mol. A novel kinetic method of determinating trace cerium has been established based on the above reaction. The conditions of the determination are as follows: 4.0×10-5mol/l SAF, 0.010% H_2O_2, 2.0×10-2 mol/l NaOH and 50℃. The calibration curve is linear for 0.04 μg/ml～0.44μg/ml Ce^3+, and the detection limit is 0.02μg/ml. As cerium content in a solution is less than 0.16μg/ml, light rare earths of 3～8-fold cerium, heavy rare earths of 5～11-fold cerium, and equal amount of uranium and thorium do not interfere with the determination of cerium. Cerium contents in the synthetic samples have been determined, and the results are satisfactory.