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在微酸性条件下,铈(Ⅲ)与铬(Ⅵ)的反应可诱导铬(Ⅵ)-碘化钾氧化还原慢反应;用停流光度法以Ⅰ_3~-淀粉络合物为指示剂研究了该诱导反应的动力学,据此提出了一种测定铈(Ⅲ)的动力学-停流光度法,并建立了最佳测定条件为:[Cr(Ⅵ)]=4.2×10~(-3)mol/L,[Ⅰ~-]=3.0×10~(-2)mol/L,pH=2.0,停流180 s,反应温度25℃;测定铈(Ⅲ)的线性范围为0～1.8μg/ml,检测限为0.008 μg/ml。除Eu(Ⅱ)外,其余稀土离子不影响测定。测定了硝酸钍及废催化剂中的铈含量。结果满意,样品加标回收率为97.3%～103.5%。相对标准偏差为1.3%～1.6%。
The reaction of cerium (Ⅲ) with chromium (Ⅵ) can induce the slow reaction of chromium (Ⅵ) -potassium iodide redox reaction under slight acidic conditions. The induction of this reaction was studied by using stop-flow spectrophotometry with Ⅰ_3 ~ starch complex as indicator Kinetics of kinetic-stop-flow spectrophotometry for the determination of cerium (Ⅲ) was proposed and the optimum conditions were established as follows: [Cr (Ⅵ)] = 4.2 × 10 -3 mol /L,[Ⅰ~-]=3.0×10~(-2)mol/L,pH=2.0, stopping flow 180 s, reaction temperature 25 ℃. The linear range of cerium (Ⅲ) was 0 ~ 1.8μg / ml , The detection limit was 0.008 μg / ml. In addition to Eu (Ⅱ), the other rare earth ions do not affect the determination. The cerium content in thorium nitrate and spent catalyst was determined. The results are satisfactory, the sample recovery was 97.3% ~ 103.5%. The relative standard deviation was 1.3% ~ 1.6%.