内标法与外标法测定废气中挥发性有机化合物

目前采用热脱附-气相色谱-质谱法测定废气中挥发性有机化合物时多使用外标法。实验对比了内标法与外标法测定时存在的差异,发现大多数VOCs内标法的回收率均高于外标法,且内标法的相对标准偏差普遍小于外标法,内标法测定的准确度和精密度均优于外标法。内标法的标准曲线可使用更长时间,对于大量样品的测定非常有利;而外标法必须每次测定时重新绘制新曲线。故废气中VOCs测定工作推荐使用内标法定量。

Comparison of internal and external standard method used for determination of VOCs in waste gas

At present,the external standard method （ESTD）is mostly used to determine volatile organic compounds（VOCs）in waste gas by thermal desorption-gas chromatography-mass spectrometry. The difference between the internal standard method（ISTD）and ESTD were compared by experiment. It is found that the most recovery rate of VOCs via ISTD is higher than that via ESTD,the relative standard deviation of ISTD is generally smaller than that of ESTD,and the accuracy and precision of ISTD are better than that of ESTD. The standard curve of ISTD can be used for a longer period of time,which is very beneficial for determination of a large number of samples;whereas that of ESTD must be redrew for each time. Therefore,ISTD is recommended for quantified determination of VOCs in waste gas.