热脱附-气质联用法测定环己酮装置废气中VOCs的研究

Determination of VOCs in exhaust gas of cyclohexanone unit by thermal desorption-gas chromatography/mass spectrometry

采用热脱附-气相色谱/质谱(TD-GC/MS)法,首先对试样进行吸附并经加热脱附解析,再经过InterCap-5MS色谱柱(60 m×0.25 mm×0.25μm)分离,利用质谱的全扫描模式定性,选择离子扫描模式进行定量分析,测定环己酮装置废气中6种挥发性有机物(VOCs)含量,探讨了热脱附条件对测定结果的影响,并研究了分析方法的准确度、精密度和检出限。结果表明:采用TD-GC/MS法测定环己酮装置废气中6种VOCs含量,合适的吸附管为美国PerkinElmer公司生产的Tenax TA吸附管,冷阱脱附温度为300℃,冷阱脱附时间为5 min;合适的热脱附条件下,废气中6种VOCs在5.0~100.0 ng范围内线性关系良好,相关系数均大于0.9987,其方法检出限为1.07~2.33 ng,相对标准偏差为1.85%~8.21%,加标回收率为73.2%~124.0%,可以满足环己酮装置废气中VOCs的检测要求。

The contents of six volatile organic compounds(VOCs)in the exhaust gas of cyclohexanone unit were determined by thermal desorption-gas chromatography/mass spectrometry(TD-GC/MS)method which comprised the qualitative analysis using the full scanning mode of mass spectrometry and quantitative analysis using the ion scanning mode after sample absorbing and thermal desorbing and separating through InterCap-5MS column(60 m×0.25 mm×0.25μm).The influence of thermal desorption conditions on the determination results was discussed.And the accuracy,precision and detection limit of the analytical method were studied.The results showed that the suitable adsorption tube was Tenax TA adsorption tube produced by PerkinElmer Company in the United States,and the cold trap desorption temperature and time was 300℃and 5 min,respectively,for TD-GC/MS determination of the six VOCs contents in the exhaust gas of cyclohexanone unit and under the suitable thermal desorption conditions,the linearity of the six VOCs in the exhaust gas was good in the range of 5.0-100.0 ng and the correlation coefficient was above 0.998,and the detection limit of the method was 1.07-2.33 ng,the relative standard deviation was 1.95%-8.21%,and the standard addition recovery rate was 73.2%-124.0%,which can meet the detection requirements of VOCs in the exhaust gas of cyclohexanone unit.