The sources of uncertainty for the kjeldahl method for determination of protein in soybean powder were investigat?ed by analyzing whole determination procedure. Each uncertainty component was modeled,synthesized. A method for the evaluation of uncertainty of protein in soybean powder was developed. The uncertainty was attributed to five sources. The de?scending order of their impacts was measurement repeatability,sample weighting,titration volume of sample solution, transfer volume of sample solution and hydrochloric acid standard titrimetric solution. The results of uncertainty evaluation showed the protein content to be(39.0±0.6)g/100g(k=2).%通过对凯氏定氮法测大豆粉中蛋白质含量的测定过程的研究,确定测定结果的不确定度.建立不确定度的数学模型,对各不确定度分量进行合成和扩展,最终建立大豆粉中蛋白质的不确定度评定方法.影响测量结果不确定度的因素共有5项,按其影响大小顺序排列分别为测量重复性、试样质量、样液滴定体积、样液移取体积以及盐酸标准溶液浓度.其不确定度报告为大豆粉中蛋白质含量为:(39.0±0.6)g/100g,包含因子k=2.
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