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 U95=22.08 μg/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.
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