Study On Monitoring Method Of Trimethylbenzene In Exhaust Gas And Atmosphere

A new method was established for determination of trimethylbenzene(1,3,5-Trimethylbenzene,1,2,4-Trimethylbenzene,1,2,3-Trimethylbenzene)in ambient air and stationary source.The trimethylbenzene were sampled by activated charcoal adsorption,desorpted by carbon disulfide and qualitatively analyzed and quantitatively detected by capillary column gas chromatograaphy.And in order to provide technical support for the development of relevant environmental standards and environmental protection work.According to the recovery to study on the condition,which are sample collection,storage,desorption and analysis.The detection limit,precision and accuracy were determined,and the method was tested with actual samples.The method was verified by six laboratories.The conclusion is as follows:The sampling flow rate was seted at 0.2 L/min to 1.0 L/min;and samples can be stored at 4 ℃ for 4 days.The desorption condition of the sample was static desorption,which needs to last 0.5 h to 1 h.The common laboratory solvents(dichloromethane,trichloromethane,carbon tetrachloride,methanol,ethylene glycol,acetonitrile,ethyl acetate,acetone,n-hexane)have no obvious interference with the determination of trimethylbenzene.When the sampling volume was 30 L,the method detection limits were between 0.003mg/L and 0.006mg/L,and the lower limits were between 0.012mg/L and 0.024mg/L.The relative standard deviation was between 1.84%~4.63%;the recovery rate were between 94.0%~ 109.4%.For the actual sample test: trimethylbenzene emitted by automobile manufacturing industry,automobile maintenance industry(4S)and wood furniture manufacturing industry are feasible in the exhaust cylinder and the factory boundary.The contribution of oil paint to trimethylbenzene emissions was higher than that of water-based paint.Therefore,we recommend the production of water-based paint instead of oil paint,which can reduce the trimethylbenzene emissions.The maximum value of detection limit obtained by 6 laboratories was the detection limit of this method.For ambient air,when the sampling volume is 30 L,the detection limit of this method is 0.004 mg/m3 ~ 0.006 mg/m3,and the lower limit is 0.016 mg/m3 ~ 0.024 mg/m3.For exhaust gas,when the sampling volume is 10 L,the detection limit of this method is 0.02 mg/m3,and the lower limit is 0.08 mg/m3.A total of 6 parallel measurements were made in six laboratories with concentrations of 0.0333 mg/m3,0.333 mg/m3 and 3.33 mg/m3 respectively.The range of relative standard deviation was 1.8% ~ 5.6%,1.5% ~ 4.6%,1.5% ~ 3.9%.The relative standard deviation range between laboratories is 3.6% ~ 5.2%,2.8% ~ 3.7%,1.8% ~ 2.3% respectively.The reproducibility limit ranges from 2.8×10-3mg/m3 to 4.0×10-3mg/m3,2.5×10-2 mg/m3 to 2.9×10-2 mg/m3,0.26 mg/m3 to 0.27 mg/m3,the reproducibility limit ranges from 5.0×10-3mg/m3 to 5.8×10-3mg/m3,3.4×10-2 mg/m3 to 3.8 ×10-2 mg/m3,and 0.30 mg/m3 to 0.31 mg/m3.Six laboratories analyzed and measured blank labeled samples with concentrations of 0.0333 mg/m3,0.333 mg/m3 and 3.33 mg/m3 respectively.The final value range of relative error was-6.8% ~ 18.7%,-10.2% ~ 4.9%,and-6.7% ~ 6.5%.The final value range of the standard recovery rate is 93.1% ~ 118.7%,89.7% ~ 105.1%,93.5% ~ 106.5%.