微孔板法测定乳粉中叶酸含量的不确定度分析

Analysis of uncertainty in determination of folic acid in milk powder by microplate method

目的:对微孔板法测定乳粉中叶酸含量的不确定度进行分析评估。方法:按GB 5009.211—2022中微孔板法测定婴儿配方乳粉中叶酸含量,依据JJF 1059.1—2012、CNAS-CL01-G003:2021和CNAS-GL05:2011等不确定度评定方法和指南对影响检测结果的各种试验因素进行分析、计算,得到合成标准不确定度及扩展不确定度。结果:扩展不确定度U 95=22.08μg/100 g(k=2),样品中叶酸含量为(282.33±22.08)μg/100 g。不确定度主要来源于接种微孔板过程、标准曲线拟合和测量重复性。结论:移液器的准确度和微生物因素对试验结果影响较大,需保证仪器质量并严格按照标准化流程操作以降低不确定度。

Objective:To analyze and evaluate the uncertainty of the determination of folic acid content in milk powder by microplate method.Methods:The content of folic acid in infant formula milk powder was determined by microplate method according to GB 5009.211—2022"National Standard for Food Safety-Determination of Folic Acid in Foods".Various experimental factors affecting the test results were analyzed and calculated according to the uncertainty evaluation methods and guidelines such as JJF 1059.1—2012,CNAS-CL01-G003:2011 and CNAS-GL05:2011,and the synthetic standard uncertainty and expanded uncertainty were obtained.Results:The expanded uncertainty U 95=22.08μg/100 g(k=2),and the folate content of the sample was(282.33±22.08)μg/100 g.The uncertainty mainly comes from the process of microplate inoculation,the fitting of standard curve and the repeatability of measurement.Conclusion:The accuracy of pipettes and microbial factors have a great impact on the experimental results,so it is necessary to ensure the quality of the instrument and strictly follow the standardized procedures to minimize the uncertainty.