电感耦合等离子体质谱测定婴幼儿配方乳粉中铝的不确定度评定

Uncertainty evaluation of determination of aluminum in infant formula milk powder by inductively coupled plasma-mass spectrometry

目的评定电感耦合等离子体质谱(inductively coupled plasma-mass spectrometry,ICP-MS)法测定婴幼儿乳粉中铝的不确定度。方法奶粉样品经微波消解后,以钪作内标,用ICP-MS测定样品中铝的含量。建立相应数学模型,对检测方法的定量限、精密度、回收率等指标进行验证,同时分析测定过程中的不确定度来源,并评定各标准不确定度的分量。结果本方法测定婴幼儿乳粉中铝含量的定量限为0.484 mg/kg,此含量水平的相对标准偏差(relative standard deviation,RSD)为8.66%,在0.25、1、2μg的加标范围内,回收率为93.13%~109.67%;样品扩展不确定度为0.040 mg/kg(k=2);其测定结果为(0.542±0.040)mg/kg。结论 ICP-MS法操作简单、定量限低、分析时间短,适合用于测定婴幼儿配方乳粉中铝的含量。影响检测结果不确定度的主要因素为测量重复性、加标回收率以及标准物质。

Objective To evaluate the uncertainty of determination of aluminum in infant formula milk powder by inductively coupled plasma-mass spectrometry （ICP-MS）. Methods After microwave digestion of the milk powder sample, helium was used as the internal standard and the aluminum content in the sample was determined by ICP-MS. A mathematical model was established to verify the limit of quantification, precision, and recovery rates of the detection methods. The sources of uncertainty in the measurement process were analyzed and the weight of each uncertainty component was assessed. Results The limit of quantification was 0.484 mg/kg and relative standard deviation （RSD） was 8.66%. The recoveries at 2 spiked levels （0.25, 1, 2 μg） were 93.13%-109.67%. The extension uncertainty was 0.040 mg/kg （k=-2）, and the result was （0.542 ± 0.040） mg/kg. Conclusions ICP-MS is simple, with limit of quantification and short analysis time, which is suitable for the determination of aluminum in infant formula milk powder. The main factors affecting the uncertainty of determination results are repeatability of measurement, recovery of standard addition and certified reference materials.