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在pH值为4.5的HAc-NaAc缓冲溶液介质中,以硫脲为活化剂,痕量铈(Ⅳ)可催化高碘酸钾氧化亮绿SF褪色反应。据此,建立了催化动力学光度法测定痕量铈的新方法。考察了介质、试剂用量、反应温度、反应时间及共存离子的影响,确定了测定波长为632 nm等最佳实验条件。在选定的实验条件下,测得反应的表观活化能为91.2 kJ/mol,常见元素不干扰测定;Ce(Ⅳ)的质量浓度在0～0.18μg/mL范围内与lg(A0/A)呈良好的线性关系,方法的检出限为5.04×10-10g/mL。用于粮食样品中痕量铈的分析,6次测定的标准偏差≤7.65%,样品加标准回收率在94.4%～103.3%。
In the HAc-NaAc buffer solution with pH 4.5, thiourea as activator, trace amounts of cerium (IV) catalyzed the oxidation of bright green SF by potassium periodate. Based on this, a new method for the determination of trace cerium by catalytic kinetic spectrophotometry was established. The effects of medium, reagent amount, reaction temperature, reaction time and coexisting ions were investigated. The optimal experimental conditions were determined at 632 nm. Under the selected experimental conditions, the apparent activation energy of the reaction was 91.2 kJ / mol, and the common elements did not interfere with the determination. The mass concentration of Ce (Ⅳ) was in the range of 0 ~ 0.18μg / mL and lg (A0 / A ) Showed a good linear relationship, the detection limit of the method was 5.04 × 10-10g / mL. For the analysis of trace cerium in food samples, the standard deviation of 6 determinations was ≤7.65%, and the standard recovery of samples was between 94.4% and 103.3%.