凯氏定氮法测定固体饮料中蛋白质含量的不确定度评定

[目的]对凯氏定氮法测定固体饮料中蛋白质含量的不确定度进行评定。[方法]根据JJF 1059.1—2012标准中要求,建立了凯氏定氮法测定固体饮料中蛋白质含量的测量不确定度的数学模型,分析了凯氏定氮法中不确定度的主要来源,对已识别来源的不确定度分量进行分析评价。[结果]固体饮料中蛋白质含量为11.60%,扩展不确定度为0.46%(95%,k=2)。测量结果的不确定度主要来源于测定样品实际消耗硫酸标准溶液的体积与测量重复性,标准溶液的影响次之,样品质量、取样体积与定容的体积带来的影响可忽略不计。[结论]系统介绍了蛋白质测量不确定度的评定过程,提高了检测数据的可靠性和一致性。

Evaluation of Uncertainty in Determination of Protein Content by Kjeldahl Method in Solid Beverage

[Objective] The uncertainty in determination of protein content by Kjeldahl method in solid beverage was evaluated.[Method] According to the requirements of JJF 1059.1-2012 standard, a mathematical model for uncertainty in determination of protein content by Kjeldahl method in solid beverage was established, various sources of uncertainty were analyzed, the uncertainty components of identified sources are analyzed and evaluated.[Result] The concentration of protein was 11.60% and the expanded uncertainty was 0.46 %(95%, k=2).The uncertainties of measurement result were mainly from volume determination of the actual consumption of sulfuric acid solution and measurement repeatability, the influence of standard solution on the second, the sample quality, the influence brought by sample volume and volume of constant volume was negligible.[Conclusion] The evaluation process of protein measurement uncertainty is introduced systematically, and the reliability and consistency of the data are improved.