分光光度法测定饲料中尿素不确定度评定

Uncertainty evaluation for the determination of urea in feed by spectrophotometry

基于对二甲氨基苯甲醛分光光度法(GB/T 36859–2018)测定饲料中尿素含量,对测定结果的不确定度进行评定。根据国家计量技术规范JJF 1059.1–2012《测量不确定度评定与表示》的要求,以检测原理为基础建立数学模型,分析测定过程中引入的各项不确定度,计算合成标准不确定度和扩展不确定度。当饲料中尿素含量为0.98%时,扩展不确定度为0.082%(k=2)。该检测方法的不确定度主要来源于标准工作曲线拟合引入的不确定度,其次为测量重复性和系列标准工作溶液配制所引入的不确定度。

The content of urea in feed was determined based on p-dimethylaminobenzaldehyde spectrophotometry(GB/T 36859–2018).The uncertainty of measurement results was evaluated.According to evaluation and expression of uncertainty in measurement(JJF 1059.1–2012),a mathematical model was established based on the detection principle.The various components of uncertainty in the measuring process of determining of urea content in feed were analyzed,and the combined uncertainty and extended uncertainty were calculated.The expanded uncertainty was 0.082%(k=2)as urea content in the feed sample was 0.98%.The major factor of uncertainty in measurement of this method is the standard curve fitting,and the minor ones are the repeatability of measurement and the preparation of urea standard solution.