石墨炉原子吸收光谱法测定农业地质调查土壤样品中镉的不确定度评定

Uncertainty Evaluation of Measurement Results for the Determination of Cadmium in Soil Samples by Graphite Furnace Atomic Absorption Spectrometry

用实例对石墨炉原子吸收光谱法测定土壤样品中镉元素的不确定度进行评定,采用《测量不确定度评定与表示指南》对测量结果进行评估。分析了不确定度的主要来源,包括测量浓度的不确定度、体积的不确定度、称量不确定度及测量重复性引起的不确定度。评估了镉含量的合成标准不确定度和扩展不确定度。对于镉含量为0.42×10-6的土壤样品,其扩展不确定度为0.04×10-6。

Based on 〈 The Guide of Uncertainty Evaluation and Denotation for Measurements 〉 , uncertainty evaluation of measurement results for the determination of cadmium in soil samples by graphite furnace atomic absorption spectrometry （GFAAS） was carried out with some examples. The results show that the main sources of the total uncertainty comes from the fraction uncertainties of sample weighting, preparation of various chemical solutions, the certified values of standard reference materials, the instrument stability and etc.. The total uncertainty for the determinations of cadmium by GFAAS was combined and the expanding uncertainty was calculated with value of 0.04 × 10^ -6 for the soil sample with cadmium content of 0.42 × 10^ -6.