二十碳四烯酸（ARA）作为婴儿配方奶粉普遍添加的可选择性成分,是食品安全检测的必检项目。本文通过气相色谱法（外标法）测定婴儿配方奶粉中的ARA含量,依据测定结果合成不确定度为2.73%, 扩展不确定度为5.46%,ARA含量测定结果为（0.264±0.007）g（k=2）。经分析表明,影响婴儿配方奶粉中ARA含量的不确定度主要来源于样品重复检测（分量不确定度2.68%）,次要来源于标准溶液（分量不确定度0.40%）与样品处理（分量不确定度0.31%）,气相色谱仪器（分量不确定度0.00002%）影响最小。为提高检测婴儿配方奶粉中ARA含量的准确度,有必要通过样品重复检测、专人专区专用具配制标准溶液、样品处理过程中规范操作动作和习惯等综合实现。

As an optional ingredient commonly added to infant formula,arachidonic acid （ARA） is also a necessary item in the food safety test of infant formula. To analyze the content uncertainty of ARA in infant formula by gas chromatography,the uncertainty components was assessed through the determination of the process of repeated measurement,the preparation of sample,the preparation of standard solutions and testing instruments according to regulation of Evaluation and Expression of Uncertainty in Measurement. The synthetic uncertainty was 2.73%,and the expanded uncertainty was 5.46%. The content of ARA in infant formula was （0.264±0.007）g （k=2）. The results showed that the uncertainty of the measurement results of ARA content in infant formula mainly came from the repeated determination of sample （2.68% uncertainty of component）, the influence of standard solution （0.40% uncertainty of component） and the sample treatment （0.31% uncertainty of component）,while the influence of gas chromatography instrument （0.00002% uncertainty of component）was the least. In the detection process, he uncertainty brought by the manual operation of the experimenter has the greatest impact on the accuracy of the detection results,and second focus is on standard solution preparation and sample handling.