电感耦合等离子体质谱法测定烟草中6种元素的不确定度

Uncertainties in Measurement of Six Elements in Tobacco by Inductively Coupled Plasma Mass Spectrometry

为提高烟草中铬(Cr)、镍(Ni)、砷(As)、硒(Se)、镉(Cd)和铅(Pb)6种元素检测结果的准确性,依据JJF 1059.1—2012《测量不确定度评定与表示》,对电感耦合等离子体质谱法(ICP-MS)测定烟草中6种元素的测量不确定度进行了评定。采用因果关系图系统分析影响不确定度的各因素,在此基础上构建了ICP-MS法测量不确定度的评定方案,并通过数学模型评定了各不确定度分量。结果表明:1Cr、Ni、As、Se、Cd、Pb的测定值分别为1.41、3.26、0.42、0.69、1.97、4.11μg/g,在95%包含概率下其扩展不确定度分别为0.10、0.21、0.03、0.10、0.13、0.33μg/g;2影响测量不确定度的因素主要有方法回收率、测量重复性、最小二乘法校准曲线拟合以及标准溶液配制;3采用称量法配制标准溶液、选择合适的标准工作溶液浓度范围以及控制漂移确保仪器稳定性,可进一步提高分析的精准度。

In order to promote the accuracy of test results, the uncertainties in measurement of chromium （Cr）, nickel （Ni）, arsenic （As）, selenium （Se）, cadmium （Cd）, and lead （Pb） in tobacco samples by inductively coupled plasma mass spectrometry （ICP-MS） were evaluated according to JJF 1059.1-2012 Evaluation and expression of uncertainty in measurement. The factors affecting the uncertainty were analyzed systematically with a cause-and-effect diagram, a procedure for assessing the uncertainty in the measurement was then developed, and the uncertainty of individual component was estimated with mathematic models. The results showed that： 1 ） The determined values for Cr, Ni, As, Se, Cd, and Pb were 1.41, 3.26, 0.42, 0.69, 1.97 and 4.11 μg/g, respectively; their expanded uncertainties at a confidence level of 95% were 0.10, 0.21, 0.03, 0.10, 0.13, and 0.33 μg/g, respectively. 2） The major factors influencing measurement uncertainty included recovery, repeatability, calibration curve fitting, and standard solution preparation. 3） The precision and accuracy of test results could be improved by preparing standard solution with gravimetric method, choosing a proper concentration range for standard working solution, and ensuring the stability of instrument by minimizing drift.