原子吸收光谱法测定钼酸铵中钾的不确定度评定

Evaluation on Uncertainty of Potassium Content in Ammonium Molybdate Measured by Atomic Absorption Spectrometry

钼酸铵中钾的含量高低是衡量钼酸铵质量优劣的一个重要指标,因此,必须要求分析测试结果准确可靠。分析测试结果的质量如何,测量不确定度就是一个衡量尺度,它表征合理地赋予被测量值的分散性。本文采用原子吸收光谱法对钼酸铵中钾量进行了测定,并对其测量结果的不确定度进行了评定。对引入该方法不确定度的相关来源进行了探讨,识别了各不确定度来源,主要对测量结果重复性、样品称量、定容体积、标准溶液、工作曲线等引入的不确定度进行了分析、计算和评定,合成标准不确定度为0.000 78%,计算出来的扩展不确定度为0.002%,测定的钼酸铵中钾量的质量分数为(0.021±0.002)%。评定结果表明,不确定度的主要来源为重复性测定和工作曲线,其他方面引入的很小,可以忽略不计。重复性测定关键在于原子吸收仪器的稳定性,工作曲线方面要求准确线性好,这两方面的工作是重点。

Potassium content in ammonium molybdate is an important fator affecting the product quality.It is essential to get exact and credible result of the potassium content.Measurement uncertainty can evaluate the quality of the results.In this research,the potassium content was determined by atomic absorption spectrometry,and the measurement uncertainty was evaluated.The uncertainty sources,such as repeatability,sample weighing,constant volume,standard solution and working curve,were calculated,discussed and evaluated.The total standard uncertainty was 0.000 78%,and the calculated expanded uncertainty was 0.002%.The measured potassium content was 0.021%±0.002%.The results show that the repeatability and calibration curve are main uncertainty sources.The repeatability is mainly affected by the stability of the atomic absorption spectrometer and the working curve should be exact and linear,they must be specially noticed in the determination process.