Research And Application Of Rapid Detection Method Of Nitrobenzene Compounds In Air

Nitrobenzene compounds were highly toxic semi-volatile organic compounds and widely used in the fields of medicine,pesticides,dyes,and chemicals.Nitrobenzene compounds in the ambient air generally exist in specific workplaces or emergencies.The hazards to human health and environmental pollution in the workplace cannot be ignored.Therefore,the development of rapid,efficient,and accurate methods for detecting nitrobenzene compounds in ambient air was very important for environmental monitoring and protection of human health.Needle trap device（NTD）was a needle-shaped solid-phase micro-extraction sampling technology,which has the characteristics of fast,simple operation,no solvent extraction,etc.,combined with GC-MS to detect the volatilization in the environment VOCs have high sensitivity and accurate detection results,and have been applied to the detection of various VOCs in the environment.This thesis selects seven nitrobenzene compounds in the air(nitrobenzene NB,o-nitrotoluene ONT,m-nitrotoluene MNT,p-nitrotoluene PNT,o-nitrochlorobenzene ONCB,p-nitrochlorobenzene MNCB,p-Nitrochlorobenzene（PNCB）for the target to establish GC-MS method for simultaneous determination of seven nitrobenzene compounds,and NTD-GC-MS method to quickly sample-determining nitrobenzenecompounds in the environment.Finally,application of established NTD-GC-MS method to detect and analyze nitrobenzene compounds in the air of the auto repairing facilities was conducted.The following main results are obtained:1.Establishing GC-MS method for the rapid determination of seven nitrobenzene compounds.Through comparative experiments,the Equity-5 capillary column was selected,and the instrument parameters were optimized.The instrument parameters for simultaneous determination of seven nitrobenzene compounds by GC-MS were determined.The final optimized parameters: the inlet temperature was250 ℃,Splitless injection,split ratio was 15,column flow rate was 1.3ml·min^-1;heating program was: initial temperature 50 ℃,9 ℃·min^-1 to210 ℃ for 1 min,then 15 ℃·min^-1 rise to 250 ℃ for 1 min.A chromatographic peak with good separation can be obtained,and all substances can be separated in 13 minutes.The linear coefficient of the standard curve of nitrobenzene compounds with different concentrations(0.01 ～ 2.0 μg·m L^-1)is 0.9990 ～ 0.9995,the detection limit of the instrument is 0.0001～0.0014 μg·m L^-1,and the limit of quantification is0.001～0.007 μg·m L^-1.The relative deviation was 5.3 to 9.8%.2.Establishing NTD-GC-MS method for a rapid sampling-detection method for the determination of nitrobenzene compounds in the environment.Through optimization experiments,itwas determined that the desorption time was 4 min,the desorption temperature was 270 ℃,the sampling rate of NTD was 4 m L·min^-1,and the concentration of seven nitrobenzene compounds was good at 1～200ng·L^-1.The linear correlation coefficient is 0.9993-0.9997.The standard addition experiments for different concentrations of air samples showed that the recovery rate of seven nitrobenzene compounds was 87.4% ～104.5%,and the relative standard deviation was 4.3%～12.1%,indicating that NTD-GC-MS was used to determine nitrobenzene in the air.The compound-like method is feasible and accurate,and the method can be used to obtain fast,efficient and accurate detection results.3.Application of NTD-GC-MS method for rapid detection and analysis of nitrobenzene compounds in the air of auto repairing facility.NTD-GC-MS was used to detect and analyze the nitro compounds in the air of three different auto repair plants in Guangzhou.The test results of the three auto repair plants were basically the same,and both NB and PNCB could be detected.The concentration of NB in??three auto repair plants is between 10.01±1.23 ng·L^-1 ～113.99±28.09 ng·L^-1,and the concentration of PNCB is between10.57±0.54～34.56 ± 8.26 ng·L^-1,among which the sampling point 1 is organized exhaust emissions,and sampling points 2 and 3 are organized exhaust emissions.According to the “Comprehensive Emission Standards for Air Pollutants”（GB16297-1996）,the maximum concentration limit ofnitrobenzene compounds in organized exhaust gas is 20 mg·m-3,and the maximum concentration limit of unorganized exhaust gas is 0.050 mg·m-3,the concentration of unorganized exhaust gas NB at sampling point 3(113.99±28.09 ng·L^-1)exceeds the maximum concentration limit of the national standard,and the NB and PNCB of the other sampling points do not exceed the national standard maximum concentration limit.NTD-GC-MS samples the nitrobenzene compounds in the auto repair plant.The sampling time was 25 minutes,and the GC-MS desorption can produce the test results within 10 minutes,enabling fast and efficient sample analysis.