微波消解-石墨炉原子吸收法测定水产制品中铬含量的不确定度评定

摘要

Objective To evaluate the uncertainty for determination of chromium content in aquatic products,so as to provide a more standardized method for assessment of uncertainty in laboratories.Methods Taking the roasted cod fillet as an example,the content of chromium in food was determined by microwave digestion-graphite furnace atomic absorption spectrometry with reference to GB 5009.123-2014 National food safety standard Determination of chromium in food.The uncertainties introduced in the experiment were analyzed,and the synthetic standard uncertainty and expanded uncertainty were calculated.Results The main factors influencing the evaluation results were the standard solution formulation,standard curve fitting and sample repeatability measurement process,in which the uncertainty introduced by the repeatability measurement of the sample had the greatest effect on the final uncertainty.The chromium content in sample was 419.60 μg/kg,the relative uncertainty was 10.526 μg/kg,the expanded uncertainty was 21.05 μg/kg (k=2),and the result could be expressed as (419.60±21.05) mg/kg (k=2,P=95％).Conclusion Through the evaluation of uncertainty,we can find possible problems in the measurement process to standardize the operation,and reduce the introduced uncertainty,so that the test results will be more reliable.%目的 评定水产制品中铬含量测定的不确定度,为食品检验实验室提供更规范的不确定度评定方法.方法 以烤鳕鱼片为例,参照GB 5009.123-2014《食品安全国家标准食品中铬的测定》用微波消解-石墨炉原子吸收光谱法测定食品中铬含量,对实验过程中引入的不确定度各分量进行分析,并计算合成标准不确定度及扩展不确定度.结果 对评定结果产生影响的主要因子是标准溶液配制、标准曲线拟合和样品重复性测量过程,其中样品的重复性测量引入的不确定度对最终不确定度影响最大.分析得该样品中铬含量为419.60 μg/kg,相对合成不确定度为10.526 μg/kg,扩展不确定度为21.05 μg/kg(k=2),最后结果表示(419.60±21.05) mg/kg(k=2,95％置信水平).结论 通过不确定度的评定,查找测量过程中可能存在的问题以规范操作,降低引入的不确定度,使检测结果更可靠.