原子荧光法测定苹果中总汞和总砷含量不确定度评定

Evaluating Uncertainty in Determination of Total Arsenic and Total Mercury in Apple by Atomic Fluorescence Spectrometry

本文旨在建立原子荧光法测定苹果中总砷和总汞含量不确定度评定的方法。首先通过分析在测定过程中影响不确定度的各个因素,接着对这些因素的不确定度进行评估和量化,最后按数学模型计算出原子荧光法测定苹果中总汞和总砷含量,合成不确定度和扩展不确定度。原子荧光法测定苹果中总汞和总砷含量分别为5.256和189.750μg/kg;相对扩展不确定度分别为14.694%和6.748%;结果表达分别为(5.256±0.772)和(189.750±12.804)μg/kg。不同浓度的待测样品要合理选择标准曲线的对应的浓度点;提高仪器稳定性,增加重复检测样品的次数;合理选择标准溶液的配制方法和移液器非常重要;总砷的测量值比总汞的测量值更接近真值,可信度更高。

To evaluate the uncertainty in determination of total arsenic and total mercury in apple by atomic fluorescence spectrometry.The influence factors of uncertainty in the cource of determination were analyzed and considered.According to mathematical model,the components of uncertainty and the combined uncertainty were calculated.The concentration of total arsenic and total mercury in apple was respectively 5.256 and 189.750μg/kg.The relative expanded uncertainty of total arsenic and total mercury was 14.694%and 6.748%respectively,and the result of the measurement was(5.256±0.772)and(189.750±12.804)μg/kg respectively.The different concentration point of the standard curve should be correctly chosen to evaluate the different concentration of sample;the repeated times of measurement and the stability of the instrument should be increased;the method and pipetting device of configuration standard soution shoule be reasonability chosen.Those factors are very important.The relative expanded uncertainty of total arsenic is smaller than the expanded uncertainty of total mercury.The measured values of total arsenic is closer to the truth than the measured values of total Mercury.