化妆品中甲醇气相色谱分析方法的不确定度评定和比较

Evaluation and Comparison of Uncertainty in the Determination of Methanol in Cosmetics by GC

对《化妆品安全技术规范》(2015年版)中有关毛细管柱气相色谱法测定甲醇含量的三种方法——气-液平衡法、直接法及蒸馏法进行不确定度的评定和比较。根据JJF1059.1-2012《测量不确定度评定与表示》,建立数学模型,考察不确定度的来源并给出量化结果,计算出合成标准不确定度和扩展不确定度,对三种方法评定结果进行比较。结果表明,三种方法测得同一化妆品样品甲醇含量分别是气-液平衡法为544±98mg/kg,直接法为540±98 mg/kg,蒸馏法为517±88 mg/kg(P=95%,k=2)。其不确定度主要来源均来自于标准溶液的配制过程(包括量器本身和使用频次),当中气-液平衡法和直接法测定结果相对准确可靠,操作简单易行。

The uncertainties in the determination of methanol in cosmetics by capillary column gas chromatography with vapor-liquid equilibria, direct method or distillation method in Safety and Technical Standards for Cosmetics（2015 Edition） were evaluated and compared. According to JJF1059-2012 Evaluation and Expression of Uncertainty in Measurement, the mathematical model was established, and each source and uncertainty component were analyzed.The combined standard uncertainty and expanded uncertainty were calculated, and the results of three methods were compared at last. The results showed that the measurement results of three methods（vapor-liquid equilibria, direct method and distillation method） for the same sample were 544±98 mg/kg, 540±98 mg/kg and 517±88 mg/kg（P=95%,k=2）, respectively. The main source of uncertainty was the preparation process of standard solutions（including the measure itself and the frequency of use）, the results of vapor-liquid equilibria and direct method were more accurate and reliable, easy to use.