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目的探讨氢化物原子荧光法测定乳粉中砷含量的不确定度评定方法,确定引入测量不确定度的主要来源,获得不确定度评定结果。方法根据《检测和校准实验室能力的通用要求》(GB/T27025—2008)第一法中的氢化物原子荧光光度法对食品中总砷及无机砷进行测定,并建立不确定度数学模型。分析测定过程中引起测量结果不确定度的来源,并计算各分量引入的不确定度和合成标准不确定度、扩展不确定度。结果当乳粉中砷含量为0.46 mg/kg时,方法引入的扩展不确定度为0.05 mg/kg。结论当测量值为临界值(测量值临近要比较的界限值)时,就必须考虑不确定度对符合性判断的影响;样品消解、标准溶液和标准曲线拟合是氢化物原子荧光法测定乳粉中砷含量不确定度的主要来源,而其他方面引入的不确定度相对较小。
OBJECTIVE To investigate the method for the determination of the uncertainty of arsenic content in milk powder by hydride generation atomic fluorescence spectrometry and to determine the main sources of measurement uncertainty and evaluate the uncertainty. Methods The total arsenic and inorganic arsenic in food were determined by hydride generation atomic fluorescence spectrometry in accordance with the first method of “General Requirements for the Capability of Testing and Calibration Laboratory” (GB / T27025-2008), and a mathematical model of uncertainty was established. Analyze the sources of the measurement uncertainty caused by the measurement, and calculate the uncertainty introduced by each component and the standard uncertainty of the synthesis, and expand the uncertainty. Results When the arsenic content in milk powder was 0.46 mg / kg, the extended uncertainty introduced by the method was 0.05 mg / kg. Conclusion When the measured value is the critical value (the measured value is close to the threshold value to be compared), the influence of the uncertainty on the judgment of conformity must be considered. Sample digestion, standard solution and standard curve fitting are determined by hydride generation atomic fluorescence spectrometry The main source of uncertainty in the arsenic content is the powder, while the uncertainty introduced in other areas is relatively small.