湿法消解-火焰原子吸收法测定小麦粉中锌含量的不确定度评定

目的评定湿法消解-火焰原子吸收法测定小麦粉中锌含量的不确定度。方法依据JJF 1059.1-2012《测量不确定度评定与表示》,分析小麦粉中锌含量测定过程中的不确定度来源,通过建立数学模型,确定不确定度传播律,量化各不确定度分量,然后计算合成不确定度和扩展不确定度。结果本研究测得的小麦粉中锌的含量为(16.1±0.8)mg/kg,k=2。测定过程的不确定度来源主要有测量结果的重复性、方法的回收率、由校准曲线求得的样品溶液中Zn浓度、样品溶液的定容体积、试样称样量和样品空白变动性引入的不确定度分量。结论湿法消解-火焰原子吸收法测定小麦粉中锌含量的不确定度主要来源于方法的回收率,其次为由校准曲线求得的样品溶液中Zn浓度和测量结果的重复性引入的不确定度,其他因素的影响相对较小。

Uncertainty evaluation of determination of zinc content in wheatflour by wet digestion-flame atomic absorption spectrometry

Objective To evaluate the uncertainty of determination of zinc content in wheatflour by wet digestion-flame atomic absorption spectrometry. Methods According to the JJF 1059.1-2012 Chinese regulation on the valuation and expression of uncertainty in measurement, the sources of uncertainty in determination of zinc content in wheatflour were analyzed. By establishing a mathematical model, the propagation law of uncertainty was determined, the uncertainty components were quantified, and then the uncertainty of synthesis and the expansion uncertainty were calculated. Results The content of zinc in wheatflour was (16.1±0.8) mg/kg, k=2. The main sources of uncertainty in the determination were analyzed as follows: the repeatability of measurement results, the method recovery, the concentrations of zinc in sample solution obtained by the calibration curve, the constant volume of sample solution, the sample weighing and the variability of the sample blank. Conclusion The uncertainty of determination of zinc in wheatflour by wet digestion-flame atomic absorption spectrometry is predominantly contributed by the method recovery, followed by the concentrations of zinc in sample solution obtained by the calibration curve and the repeatability of measurement results. Besides that, the influences of other factors are relatively small.