石墨炉原子吸收光谱法测定大米中镉含量的不确定度分析

Uncertainty analysis for the determination of cadmium content in rice by graphite furnace atomic absorption spectrometry

根据前处理和测定过程中使用的器材和实验条件,分析得到影响大米镉含量测定的主要因素,并对实验过程提出改进意见。结果显示:在石墨炉-原子吸收光谱法测定大米中镉含量过程中,重复测定引入的不确定度最高,其次为系统偏差引入的不确定度,随着样品中镉含量的增加,重复测定引入的不确定度占比减小。除此之外,影响程度较大的为标准曲线的拟合,再次为定容过程。标准品的纯度、称量过程、稀释过程引入的不确定度误差相对较小。最后得出大米样品中镉含量为(0.2430±0.03052)mg/kg。

According to the equipment and experimental conditions used in the pretreatment and determination process,the main factors affecting the determination of cadmium content in rice were analyzed,and suggestions for improving the experimental process were put forward.The results showed that during the determination of cadmium content in rice by graphite furnace atomic absorption spectrometry,the uncertainty introduced by repeated determination was the highest,followed by the uncertainty introduced by systematic deviation.With the increase of cadmium content in the sample,the uncertainty introduced by repeated determination decreased.In addition,the fitting of the standard curve had a greater impact,and then the constant volume process.The uncertainty error introduced by the purity of the standard,weighing process and dilution process was relatively small.Finally,the cadmium content in rice samples was(0.2430±0.03052)mg/kg.