石墨炉原子吸收法测定发电厂水汽中微量铁浓度的不确定度评定

Evaluation of uncertainty of trace iron content in water and steam of power plant detected by graphite furnace atomic absorption method

对石墨炉原子吸收光谱法测定发电厂水汽中微量铁浓度进行了不确定度评定。根据《化学分析中不确定度的评估指南》和《化学分析测量不确定度评定》,分析了整个测定过程中不确定度来源,计算了各不确定度分量,得到测定结果的扩展不确定度。当水样中铁的质量分数为3.67μg/L时,扩展不确定度为0.16μg/L。在各不确定度分量中,回归方程计算铁浓度引入的不确定度影响最大,必须控制好回归方程的相关系数;消解定容引入的不确定度影响很小,可以舍去。

The uncertainty of trace iron content in water and steam of power plant detected by graphite furnace atomic absorption method was evaluated. According to the files CNAS-GL06—2066 'Guidance on Evaluating the Uncertainty in Chemical Analysis'and JJF 1135—2005 'Evaluation of Uncertainty in Chemical Analysis Measurement',the sources of the uncertainty during whole measurement process were analyzed. Each component of the uncertainty was calculated,and the expanded uncertainty on the measurement result was obtained. When the mass fraction of iron in water sample is 3. 67 μg /L,the expanded uncertainty is 0. 16 μg /L. In the various uncertainty components,the uncertainty brought by using the regression equation to calculate the iron content has largest influence,so it is necessary to control the related coefficients of the regression equation well. The influence of the digestion and volume calibration process on the uncertainty is very little and can be neglected.