气相色谱法测定保健食品中二十碳五烯酸的不确定度评定

Uncertainty evaluation for the determination of eicosapentaenoic acid in healthy foods by gas chromatography

目的评定气相色谱法测定保健食品中二十碳五烯酸的不确定度。方法样品用正己烷溶解,经皂化、甲酯化后用气相色谱法检测,外标法定量,对保健食品中的二十碳五烯酸进行测定。建立数学模型对测量不确定度的来源进行分析和评定,合成不确定度。结果二十碳五烯酸含量测定的合成不确定度为4.2%,扩展不确定度为19 mg/g,测量结果为(2.2±0.2)×10~2 mg/g,k=2,置信区间为95%。通过对各不确定度分量进行分析,不确定度主要由标准系列溶液配制和样品制备过程引入。结论对气相色谱法测定保健食品中二十碳五烯酸的过程进行不确定度评定与分析,有利于检测结果准确性的提高和实验室的质量控制。

Objective To evaluate the uncertainty for the determination of eicosapentaenoic acid in healthy foods by gas chromatography. Methods Samples were dissolved with n-Hexane. After saponification and meth-esterification, samples were analyzed by gas chromatography, while eicosapentaenoic acid was quantified with external standard curve. A mathematic formula was established in order to identify and analyze the source of uncertainty. The synthetic uncertainty was assessed. Results The synthetic uncertainty for the determination of eicosapentaenoic acid was 4.2%, while the expanded uncertainty was 19 mg/g. The content of eicosapentaenoic acid was （2.2±0.2）×10^2 mg/g, k=-2, with the confidence interval 95%. Through the evaluation of each uncertainty component, the uncertainty of determination was mainly caused by preparation of standard solutions and samples. Conclusion The uncertainty evaluation for the determination of eicosapentaenoic acid in healthy foods by gas chromatography is conducive to improve the accuracy of test results and the quality control of laboratory.