气相色谱法测定藿香正气水中乙醇量的不确定度评定

Uncertainty Evaluation of Ethanol Content Detection in Huoxiang Zhengqi Tincture by Gas Chromatography

采用气相色谱法测定藿香正气水中乙醇量,评定测定结果的不确定度。建立气相色谱法测定藿香正气水中乙醇量的不确定度数学模型,分析影响测量不确定度的来源,包括无水乙醇的纯度、对照品溶液的移液定容、样品溶液的移液定容、样品重复测定和气相色谱仪,计算合成标准不确定度和扩展不确定度。当藿香正气水中乙醇量为47.44%时,扩展不确定度为0.50%(k=2,置信区间P=95%)。测量不确定度主要来源于对照品溶液和样品溶液的移液定容。测量过程中,可以通过选择精度较高的玻璃量具,并尽量将定容温度控制在20℃,以提高测定结果的准确度。

The ethanol content in Huoxiang Zhengqi tincture was determined by gas chromatography,and the uncertainty for the measurement results was evaluated.A mathematical model of uncertainty in ethanol content detection by gas chromatography was established,and the factors affecting measurement uncertainty were analyzed,including the purity of anhydrous ethanol,the pipetting and constant volume of standard solution and sample solution,the repeatability of measurement,and the instrument.The synthetic standard uncertainty and expanded uncertainty were calculated.The results showed that when the ethanol content in Huoxiang Zhengqi tincture was 47.44%,the expanded uncertainty was 0.50%(k=2,P=95%).The main sources of measurement uncertainty were the pipetting and constant volume of the standard solution and sample solution.The accuracy of the measurement results cloud be improved by selecting the glass gauge with higher precision and controlling the constant volume temperature close to 20℃.