微波消解ICP-MS测定大米中铅和镉的不确定度评定

Uncertainty Evaluation for the Determination of Pb and Cd in Rice by Microwave Digestion-ICP-MS

采用微波消解结合电感耦合等离子体质谱仪测定大米中重金属铅和镉的含量,对其测量不确定度进行分析评定。根据相关规定,分析测定大米中铅和镉的过程中不确定度来源,计算各不确定度并进行合成。结果表明,称0.5 g大米样品,定容体积50 mL,大米中铅含量为0.184 mg/kg,扩展不确定度为0.022 mg/kg(k=2);大米中镉含量为0.517 mg/kg,扩展不确定度为0.065 mg/kg(k=2)。不确定度主要来源于标准溶液配制和标准曲线拟合。

The contents of heavy metals of lead and cadmium in rice were determined by microwave digestion combined with inductively coupled plasma mass spectrometer, and the uncertainty of determination was analyzed and evaluated. According to relevant regulations, the uncertainty sources of lead and cadmium in rice were analyzed, and the uncertainties were calculated and synthesized. The results showed that in the sample weighing 0.5 g with the constant volume of 50 mL, the lead content in rice was 0.184 mg/kg, and the expanded uncertainty was 0.022 mg/kg(k=2);the cadmium content in rice was 0.517 mg/kg and the expanded uncertainty was 0.065 mg/kg(k=2). The uncertainty mainly came from the preparation of standard solution and the fitting of standard curve.