微波消解-火焰原子吸收法测定鲜果中钙含量的不确定度评定

摘要

A mathematic model for evaluating the uncertainty in the determination procedure for calcium content in fruits by microwave digestion-flame atomic absorption spectrometry （FAAS） was established. The uncertainty sources for each param- eter in the model were analyzed. The uncertainties of type A （based on the calculation of the statistical distribution of the determination results） type B （based on the estimation by experience and the probability distribution of other information） were evaluated. According to JJF 1059-1999, the component uncertainties were synthesized and extended. An expanded uncertainty of 1.18 mg/kg was obtained at the confidence probability of 95% and coverage factor of k=2. Based on the analysis of uncertainty, the preparation of standard solutions and the fitting of standard curves were the major sources of uncertainty, while sample weighing and the preparation of digestion solution revealed little effect on the final uncertainty. Meanwhile, some strategies for improving quality control were proposed.%分析微波消解．火焰原子吸收法测定鲜果中钙含量的过程，建立相应数学模型。对数学模型中各个参数进行不确定度来源分析，分别对A类不确定度（用对观测列进行统计分析的方法来评定的不确定度）或B类不确定度（用不同于对观测列进行统计分析的方法来评定的不确定度）进行评定。按照JJF1059-1999《测量不确定度评定与表示》对各不确定度分量合成和扩展，当取置信概率为95％，包含因子k=2，则其扩展不确定度为1．18mg／kg。通过对不确定度的分析，指出标准溶液配制和标准曲线拟合是不确定度的主要来源，而称量和消解液的定容过程对最终不确定度结果影响不大，并提出了质量控制改进方法。