凯氏定氮法测定人血白蛋白中蛋白质含量的不确定度评价

目的：对凯氏定氮法测定人血白蛋白中蛋白质含量的不确定度进行评价。方法：建立不确定度计算模型，对测定中的各影响因素进行考察。结果：量化了各不确定度分量并计算出合成不确定度为0．62％，取k=2，得扩展不确定度为1．2％，人血白蛋白中蛋白质含量为（104．7±1．2）％。结论：测定总氮时样品的稀释和量取以及实际消耗硫酸滴定液体积、测量重复性、硫酸滴定液的浓度标定和稀释是凯氏定氮法测定人血白蛋白含量不确定度的主要因素，通过分析上述不确定度分量对试验进行优化，可使测定结果更加可靠。

Evaluation of the Uncertainty for Content Determination of Protein in the Human Albumin by Kjeldahl Nitrogen Method

Objective： To evaluate the uncertainty for the protein content determination of human albumin by Kieldahl nitrogen method. Methods： The model for evaluation of the uncertainty was established,and the factors influencing upon the measurement were investigated. Results： The combined standard uncertainty was obtained as 0.62% by combining all standard uncertainty. The expanded uncertainty was calculated as 1.2% by using a coverage factor k = 2, and the protein content in the human albumin was determined as （ 104. 7 ± 1.2） %. Conclusion： The dilution and fetching of the sample in the determination of total nitrogen, repeatability of the measurement, as well as the consumption, standardization, and dilution of volumetric solution （ sulfuric acid） were the primary factors for the measurement of uncertainty. Optimizing the method by analyzing all factors could make the result more reliable.