液相色谱-串联质谱法测定婴儿奶粉中三聚氰胺残留量的不确定度评估

Uncertainty evaluation for the determination of melamine residues in infant formula by liquid chromatography-tandem mass spectrometry

目的对液相色谱-串联质谱法测定婴儿奶粉中的三聚氰胺的不确定度进行评估。方法以GB/T22388-2008《原料乳与乳制品中三聚氰胺检测方法》为基础改良方法,测定婴儿奶粉中的三聚氰胺。依据CNAS-GL06:2006《化学分析中不确定度的评估指南》,通过数学建模建立不确定度来源鱼骨图,分析不确定度来源并计算不确定度分量。结果当奶粉中的三聚氰胺残留量为50μg/kg时,测量不确定度为3.70μg/kg(k=2),其中液质仪器校准、重现性和偏差对不确定度影响最大。结论内标法的线性拟合对测量不确定度贡献较小,对三聚氰胺的常规检测具有重要意义。

Objective To evaluate the uncertainty for the determination of melamine residue in infant formula by liquid chromatography-tandem mass spectrometry（LC-MS/MS）. Methods Based on GB/T 22388-2008 Determination of melamine in raw milk and dairy products, the original method to measure melamine residue in infant formula was improved. According to CNAS-GL06： 2006 Guidance on evaluating the uncertainty in chemical analysis, the sources of uncertainty of the whole determination procedure were analyzed and calculated based on the mathematical model and fishbone diagram. Results When melamine residue in infant formula was 50 μg/kg, the uncertainty of measurement was 3.70 μg/kg（k=2）, and the major sources of uncertainty of measurement were the calibration of LC-MS/MS, repeatability and measuring deviation. Conclusions Standard curve fitting by internal standard method contributes little in combined uncertainty, which is significant for conventional detection of melamine.