Kjeletc 8400凯氏定氮仪测定乳粉中蛋白质的不确定度评定

目的 评定Kjeletc 8400凯氏定氮仪测定乳粉中蛋白质的不确定度。方法 采用GB 5009.5-2016第一法凯氏定氮法测定乳粉中蛋白质含量。对每个不确定度分量进行计算合成,分析影响测量不确定度的因素,同时对各不确定度分量进行评估,计算乳粉中蛋白质的标准不确定度及扩展不确定度。结果 乳粉称量、消化、蒸馏及滴定等过程均为不确定度的来源,乳粉中蛋白质含量测定的扩展不确定度为(19.3±2.7)%,k=2。结论 不确定度主要由硫酸标准溶液浓度和全自动凯氏定氮仪的仪器滴定体积的不确定度引入。

Uncertainty analysis on determination of protein in milk powder with Kjeltec 8400 protein analyzer

Objective To determine the uncertainty of protein in milk powder with Kjeletc 8400 protein analyzer. Methods The protein content in milk powder was determined by the first method of GB 5009.5-2016. Each uncertainty component was calculated and synthesized, and the factors affecting the measurement uncertainty were analyzed. At the same time, each uncertainty component was evaluated to calculate the standard uncertainty and extended uncertainty of the protein in the milk powder. Results Milk powder weighing, digestion, distillation and titration were sources of uncertainty. The extended uncertainty of protein content determination in milk powder was (19.3±2.7)%, k=2. Conclusion The uncertainty is mainly introduced by the uncertainty of the concentration of the sulfuric acid standard solution and the instrumental titration volume of Kjeltec 8400 protein analyzer.