气相色谱内标法测定甲基苯丙胺含量的不确定度评定

Evaluation of Uncertainty in Determination of Methamphetamine by GC with Internal Standard Method

目的建立气相色谱内标法测定甲基苯丙胺含量的不确定度评估方法。方法从分析测定程序着手,依据不确定度评定的指导性文件,分析了测量实验过程中引入的不确定度来源,包括测量重复性、样品、标准物质、内标物质等分量引入的不确定度,最后合成标准不确定度及获得测量结果的扩展不确定度。结果各相对不确定度分别来源于样品重复性检测为1.4%,SKF525A内标溶液配制为0.89%,甲基苯丙胺对照品溶液配制为0.85%,气相色谱仪为0.78%,样品配制为0.081%。甲基苯丙胺含量为10.4%时,其扩展不确定度为0.4%。结论甲基苯丙胺含量的不确定度主要来源于样品重复性检测、甲基苯丙胺对照品配制、气相色谱仪和内标液配制。

ObjectiveTo evaluate the uncertainty in determination of methamphetamine by gas chromatography （GC） with internal standard method.MethodsEach source of uncertainty, arising from the procedure of testing, was analyzed and conifrmed according to the guidelines of the uncertainty in measurement. Analysis of the measurement uncertainty during the experiment,including the uncertainty of calculation, measurement repeatability, standard substance, internal standard substance, sample and gas chromatography was taken. After each uncertainty component was evaluated, the combined standard uncertainty and the expanded uncertainty of the result were calculated.ResultsThe relative uncertainty brought from the measurement repeatability was 1.4 %, the one from preparation for internal standard solution of the SKF525A was 0.89%, the one from preparation for standard solution of the methamphetamine was 0.85 %, the one from gas chromatography was 0.78 %, and the one from preparation for the sample of methamphetamine was 0.081 %. The expanded uncertainty was 0.4 % when the methamphetamine content was 10.4 %.ConclusionsThe measurement uncertainty of methamphetamine comes primarily from the measurement repeatability of sample, preparation for standard solution of the methamphetamine, GC, preparation for sample and internal standard. The uncertainty from the sample preparation was relatively minimal, the uncertainty from the uniformity of the sample and peak area ratio can be ignored.