分光光度法测定乳粉中亚硝酸盐含量的不确定度评定

目的 研究分光光度法测定乳粉中亚硝酸盐的不确定度评定。方法 以乳粉为例, 参考JJF 1059.1-2012《测量不确定度评定与表示》, 对GB 5009.33-2016《食品安全国家标准 食品中亚硝酸盐与硝酸盐的测定》第二法分光光度法测定亚硝酸盐的不确定度进行评定。结果 乳粉中亚硝酸盐的含量为1.0 mg/kg 时, 测定结果的合成标准不确定度为0.042 mg/kg, 取k=2, 扩展不确定度为0.084 mg/kg, 其结果可表示为(1.0±0.1) mg/kg。结论 测量结果的不确定度主要是标准曲线拟合、标准工作液配制、试样检测重复性和测定用样液体积。前两者引入的不确定度分量贡献较大。

Evaluation of uncertainty in the determination of nitrite content in milk powder by spectrophotometry

Objective To evaluate the uncertainty of determination of nitrite content in milk powder by spectrophotometry. Methods Taking milk powder as an example, refer to JJF 1059.1-2012 Measurement and expression of measurement uncertainty, the uncertainty of the second method spectrophotometric determination of GB 5009.33-2016 Determination of nitrite and nitrate in foods of national food safety standards was assessed. Results When the content of nitrite in milk powder was 1.0 mg/kg, the synthetic standard uncertainty of the determination result was 0.042 mg/kg (k=2), and the expansion uncertainty was 0.084 mg/kg. The result can be expressed as (1.0 ± 0.1) mg/kg. Conclusion The uncertainties of the measurement results are mainly the standard curve fitting, standard working solution preparation, sample detection repeatability and measurement sample volume. The uncertainty components introduced by the former two factors contribute a lot.