半微量凯氏法测定土壤全氮量的不确定度评定

以半微量凯氏法测定土壤中全氮量为例，对测定结果的不确定度来源进行了详细分析，对测定过程中的主要不确定度分量进行了合理评定，包括样品和标准物质硼砂的称量引入的不确定度，硼砂的纯度引入的不确定度，容量瓶、移液管和滴定管的体积引入的不确定度．相关元素的摩尔质量引入的不确定度以及测量的重复性引入的不确定度。最后合成标准不确定度．通过乘以95％置信概率下的扩展因子2获得测量结果的扩展不确定度。

Uncertainty Evaluation of Measurement Results for the Determination of Total Nitrogen in Soil Samples by Semimicro-Kjeldahl Method

The uncertainty semimicro-Kjeldahl method of measurement results for the was evaluated in this example. determination of total The results show that nitrogen in soil samples by the main sources of the total uncertainty comes from the fraction uncertainties of weighting of borax standard and sample, purity of borax, volume of volumetric flask, pipette and burette, molar mass of relative elements and measurement repeatability. The total uncertainty for the determinations of total nitrogen by semimicro-Kjeldahl method was combined and its extended uncertainty was obtained via multiplying it by extended factor of 2 under confidence probability of 95%.