便携式GC-MS测定气体样品中6种典型VOCs的不确定度评定

The Uncertainty of Determination of Six Typical VOCs in Gas Sample by Portable GC-MS

以便携式GC-MS测定气体样品中6种典型挥发性有机物(VOCs)组分(苯、1,1,2-三氯乙烷、四氯乙烯、乙苯、间二甲苯和1,3,5-三甲基苯)为例,应用不确定度理论,从检测过程和计算方法的角度分析了影响测量不确定度的各种因素:标准气体定值、标准气体稀释、工作曲线的非线性及重复性测定。对各测量不确定度分量进行计算和评定,同时采用稳健统计方法对测定结果进行准确度评价。结果表明:采用便携式GC-MS测定气体样品中VOCs不确定度的主要影响因素是标准气体定值和工作曲线的非线性,其次是重复性测定,标准气体稀释引入的不确定度较小。当VOCs组分含量为200 nmol/mol浓度水平时,测量扩展不确定度为14~17 nmol/mol,测量相对扩展不确定度为7.1%~9.2%(k=2,置信水平为95%),相对误差为1.5%~4.0%。

Determination of representative components of VOCs(Benzene,1,1,2-Trichloroethane,Tetrachloroethylene,Ethylbenzene,m-Xylene and 1,3,5-Trimethylbenzene)in gas sample by portable GC-MS was taken for example in this paper.Based on the theory of uncertainty,affecting factors on uncertainty were analyzed from the angle of testing process and calculation method,including the certified reference material,diluted method,non-linearity and repeatability measurement of standard curve.And robust statistical method was used to evaluate the accuracy of the determination results.The results showed that the main influencing factors of uncertainty in determination of VOCs in gas sample by portable GC-MS were the certified reference material and non-linearity of standard curve,followed by the repeatability measurement,and the uncertainty of standard gas dilution was small.When the concentration level of VOCs components was 200 nmol/mol,the expanded uncertainty of testing was 14-17 nmol/mol,and the relative expanded uncertainty was 7.1%-9.2%(k=2,confidence level is 95%),and the relative error was 1.5%-4.0%.