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[目的]根据国家计量技术规范JJF1135-2005《化学分析测量不确定度评定》的要求,以石墨炉原子吸收法测定面粉中铅为例对测定结果的不确定度进行评定。[方法]对不确定度的主要来源包括称量的不确定度、标准物质的不确定度、体积的不确定度、标准曲线的不确定度及测量重复性引起的不确定度进行分析,并按数学模型计算出各不确定度分量、合成标准不确定度和扩展不确定度。[结果]得到石墨炉原子吸收法测定面粉中铅的不确定度,当面粉中铅含量为0.122mg/kg时,扩展不确定度为0.020mg/kg,结果表达为(0.122±0.020)mg/kg。[结论]正确选择前处理方法和熟练掌握前处理方法极其重要。定容体积、样品称量产生的不确定度非常小,对测量结果影响不大。
[Objective] According to the requirements of National Measurement Specification JJF1135-2005 “Evaluation of Uncertainty in Chemical Analysis Measurement”, the determination of lead in flour by graphite furnace atomic absorption spectrometry was carried out to evaluate the uncertainty of measurement results. [Methods] The main sources of uncertainty include the uncertainty of weighing, the uncertainty of reference material, the uncertainty of volume, the uncertainty of standard curve and the uncertainty caused by the repeatability of measurement According to the mathematical model to calculate the components of uncertainty, synthetic standard uncertainty and extended uncertainty. [Result] The uncertainty of determination of lead in flour by graphite furnace atomic absorption spectrometry was obtained. When the lead content in flour was 0.122mg / kg, the extended uncertainty was 0.020mg / kg, the result was (0.122 ± 0.020) mg / kg. [Conclusion] The correct choice of pretreatment methods and master pre-treatment methods is extremely important. The volume of constant volume, sample weighing uncertainty is very small, little effect on the measurement results.