全自动凯氏定氮仪测定蛋白饮料中蛋白质的不确定度分析

目的]减少试验过程中带来的误差,确保蛋白质含量的数据准确性。方法]采用GB 5009.5—2016第一法,凯氏定氮法测定蛋白饮料中蛋白质含量,其测量不确定度来源于样品称量、消化、蒸馏及滴定等过程。通过对各个不确定度分量的计算合成,找出影响测量不确定度的因素,并对各个不确定度分量进行评估,最终分析出样品核桃花生奶中蛋白质的标准不确定度及扩展不确定度,并描述影响核桃花生奶蛋白质测定结果各分量对其不确定度的相对贡献。结果]最终通过合成和扩展得出了核桃花生奶中蛋白质含量测定的扩展不确定度为(1.30±0.03)%。结论]不确定度主要由全自动凯氏定氮仪的仪器滴定体积的不确定度引入,说明仪器的先进性能够有效减少试验过程中的误差。

Uncertainty Analysis on Determination of Protein in Protein Drinks with Kjeltec 8400 Protein Analyzer

Objective]To reduce the errors caused by the experiment and ensure the accuracy of the protein content.Method]Protein content in protein drinks was determined by Kjeldahl method,the first method of GB 5009.5-2016,the measurement uncertainty was tracked from such experimental processes as sample weighing,digestion,distillation and titration etc..By calculation and synthesis of each component uncertainty, it figured out the factors affected the measurement uncertainty,and evaluated the uncertainty of each component,analyzed the standard uncertain-ty and expanded uncertainty of protein in protein drinks samples,and described the relative contributions which affected various components re-sults of protein in walnut and peanut milk on its uncertainty.Result]The results were combined and expanded,thus the expanded uncertainty of measurement result of the protein in walnut and peanut milk was(1.30 ±0.03)%.Conclusion]The uncertainty is mainly introduced by the uncertainty of the instrument titration volume of the automatic apparatus,indicating that the advanced nature of the instrument can greatly reduce the error in the experiment.