金矿石中铅含量的测量不确定度评定

Evaluation of Measurement Uncertainty of Lead Content in Gold Ores

本研究依据GB/T 20899.5—2021方法1火焰原子吸收光谱法测定金矿石中的铅含量,建立数学模型,分析整个测定过程中不确定度的来源。样品的称量、定容体积、稀释及标准曲线的拟合等都会引入一定的不确定度分量。本文分别通过A类或B类评定方式对这些不确定度分量进行计算,并合成标准不确定度u,在置信概率为95%的情况下,取包含因子k=2,计算得扩展不确定度U=0.05%。计算发现,B类不确定度的贡献大于A类不确定度,而B类不确定度分量贡献最大的部分为标准曲线带来的不确定度,可以通过增加标准溶液数量以及试液的测量次数来降低标准曲线带来的不确定度影响。实验表明,在条件一致的情况下,试液测量次数由3次增加到5次,扩展不确定度可由0.05%降至0.04%。

Lead content was determined by flame atomic absorption spectrometry according to method 1 of GB/T 20899.5—2021,and measurement models were established depending on the measurement program.The sources of uncertainty were analyzed,including the sample weighing,solution volume,dilution volume and the fitting of the standard curve.All the uncertainty components were calculated using type A or type B evaluation,combined to the standard uncertainty u,if the probability level is 95%,take the inclusion factor k=2 and calculate the extended uncertainty U=0.05%.It is found that the uncertainty evaluated by type B is greater than the uncertainty evaluated by type A,and the largest uncertainty source is that from working curve.An effective way to reduce U is increasing the standard solutions’number and increasing test times of standard solutions and the sample test solution.The experiment shows that under the same conditions,the number of test liquid measurements increases from 3 to 5,and the extended uncertainty decreases from 0.05%to 0.04%.