液液萃取-石墨炉原子吸收法测定食盐中铅含量的不确定度评定

The Uncertainty Evaluation of Determination of Lead in Salt by Graphite Furnace Atomic Absorption Spectrometry with Liquid-Liquid Extraction

本文建立了液液萃取-石墨炉原子吸收法测定食盐中铅含量的不确定度评定数学模型。针对液液萃取中存在的多次定容操作对结果带来的影响,分析和探讨了测定过程中不确定度来源,包括样品称量结果、待测溶液定容体积、工作曲线、测量结果的重复性和校准溶液浓度。将各分量进行合成,得到合成标准不确定度和扩展不确定度。当k=2(95%置信度水平),食盐中铅含量结果表示为(0.136±0.011)mg·kg^(-1)。结果不确定度的主要分量依次为工作曲线、测量结果的重复性和校准溶液浓度。在检验中,需要减少工作曲线定容次数和保证样品的均匀度以降低不确定度。

A mathematical model for the determination of lead by graphite furnace atomic absorption spectrometry with liquid-liquid extraction in salt was established in this paper.Considering the new influence of liquid-liquid extraction procedure,the sources of uncertainty were evaluated,including sample weighting,sample volume adjustment,standard curve,sample measurement repeatability and concentration of standard solution.Each uncertainty component was synthesized together to calculate combined standard uncertainty and expanded uncertainty.The measured contend of lead in salt sample was expressed as(0.136±0.011)mg·kg^(-1),k=2(95%confidence interval).The main sources of uncertainty in descend order were standard curve,sample measurement repeatability and concentration of standard solution.During the inspection procedure,decreasing the number of sample volume adjustment and preparing of homogenous sample should be considered.