Determination Of Chlorobenzene Compounds In Air By Dynamic Needle Trapping Gas Chromatography Mass Spectrometry

Chlorobenzenes（CBs）are a class of persistent toxic pollutants that are widely used in dyes,pesticides,chemicals,pharmaceuticals and other fields.Most of the CBs in ambient air exist in specific workplaces or in sudden environmental pollution events,and the risk to human health and environmental pollution in the workplace cannot be ignored.Therefore,it is particularly important to develop a fast,efficient,environmentally friendly,and accurate methods for detecting CBs in ambient air.In addition,CBs attached to PM_2.5 can enter the human body through breathing,and their health risks such as carcinogenicity and mutagenicity pose a potential threat to human health.At present,the pollution characteristics and sources of CBs in atmospheric particulate matter have been reported,but the study of the pollution characteristics and sources of CBs in atmospheric particulate matter in Guiyang City has not been reported.Therefore,the study of the pollution characteristics of CBs is of great significance for the protection of human health and the management of CBs pollution.The dynamic needle trap device（NTD）is a needle-based microextraction pre-treatment technique with the advantages of rapid,solvent-free extraction and simple operation.Combined with the coupling of gas chromatography-mass spectrometry（GC-MS）analytical techniques,it has been applied to the sampling and analysis of a variety of trace volatile organic compounds（VOCs）in air.In this study,three CBs（chlorobenzene CB,p-dichlorobenzene PCB,and1,2,4-trichlorobenzene TCB）in air were studied to establish a method for the simultaneous detection of three chlorobenzenes（GC-MS）and a method for the rapid detection of three trace chlorobenzenes in ambient air（NTD-GC-MS）using NTD in combination with GC-MS,and applied.The method was applied to the sampling and analysis of CBs in the air of auto repair painting workshop.In addition,this paper investigates the pollution characteristics of CBs concentration in PM_2.5 of Guiyang,probes the influence of meteorological parameters on CBs concentration and its correlation,explores the influence of wind direction on CBs concentration distribution,clarifies the possible source directions of polluted air masses,compares CBs concentration in PM_2.5 of Guiyang City with CBs concentration collected by NTD.The distribution characteristics of CBs in the gas phase and particulate matter in ambient air were investigated to provide data support for monitoring the pollution of CBs in ambient air.The main results obtained in this study are as follows:1.Study of analytical method for simultaneous detection of three chlorobenzenes by GC-MS.By comparing the separation effects of Equity-5MS and DB-17MS columns,selected DB-17MS as the chromatographic column,and the instrument parameters were optimized to determine the parameters of the three kinds of CBs simultaneously detected by GC-MS as follows:inlet temperature of 200℃,split iniection with a split ratio of 30:1,and the ramp-up procedure as follows:initial temperature of 70℃（hold for 1 min）,20t C?min^-1 to 150t C for 1 min,then 5t C?min^-1 to 200t C for 2 min,and the separation was achieved within 6 min.The linear coefficients of the three CBs were 0.995～0.998in the range of 0.100～10.0μg?m L^-1.The limits of detection（LODs）and limits of quantification（LOQs）of the method were 0.00550μg?m L^-1～0.0120μg?m L^-1 and 0.0200μg?m L^-1～0.0400μg?m L^-1,respectively,with RSD were 3.80%～9.30%.2.Study on the analytical method for the rapid detection of three chlorobenzenes in air by NTD-GC-MS.The NTD with Carboxen 1000adsorbent was used in combination with GC-MS technique for the rapid detection and analysis of three CBs in air.The sampling conditions and desorption conditions were optimized and selected to investigate the penetration volume and storage conditions of the NTD with the adsorbent Carboxen 1000 for the three CBs.The sampling rate of NTD was determined to be 4 m L?min^-1,the sampling volume was 120 m L,the desorption temperature was 280t C,the desorption time was 4 min,and the storage of needle trap samples at low temperature（4t C）could reduce the loss of targets.The results showed that good correlation coefficients（0.996～0.997）were obtained for all three CBs in the range of 2.00～50.0μg?m L^-1,with LODs of 0.000312μg?m L^-1～0.000592μg?m L^-1,RSDs of 4.12%～7.92%,and spiked recoveries of 80.0%～115%,indicating the recoveries were 80.0%～115%,indicating the feasibility and accuracy of the NTD-GC-MS method for the determination of trace CBs in air.3.Application study of NTD-GC-MS for rapid detection of chlorobenzenes in the air of auto repair painting workshop.Air samples from an auto body store in Guiyang city were collected and analyzed by NTD-GC-MS method for paint spraying.The average concentrations of CB,PCB and TCB were detected as 5.09±0.0265μg?m L^-1,2.42±0.0306μg?m L^-1 and 3.45±0.0500μg?m L^-1,respectively,which were significantly higher than the occupational health standards in China（GBZ 2.1 2007）,the time-weighted average permissible concentrations of CB and PCB in workplace air(50.0 mg?m^-3 and 30.0mg?m^-3,respectively)were significantly high.4.Study on the pollution characteristics of three chlorobenzenes in PM_2.5 in Guiyang City.The sampling time is from December 6,2021 to November 29,2022 for atmospheric PM_2.5 samples（n=121）.The daily average mass concentrations of PM_2.5 in Guiyang were 26.8±20.0μg?m^-3,which were positively correlated with the concentrations of all three CBs.The average monthly mass concentrations of CB,PCB,and TCB in PM_2.5ranged from 3.26 to 16.9 ng?m^-3,0.214 to 0.358 ng?m^-3,and 0.0159 to0.0326 ng?m^-3,respectively,with the highest values occurring in January and the lowest in August.The seasonal concentrations all showed the characteristics of high in winter and low in summer.All three CBs concentrations were negatively correlated with temperature and rainfall,but positively correlated with air pressure.However,CB concentrations were negatively correlated with humidity and wind speed,PCB concentrations were negatively correlated with wind speed and positively correlated with humidity,and TCB concentrations were positively correlated with humidity and wind speed.The results of the analysis of the rose wind diagram showed that the three CBs were distributed in all directions,but the sources of CBs were mainly concentrated between the northeast and southeast directions,probably because the polluted air masses in these regions were transmitted to the sampling points along with the atmospheric motion.The concentrations of the three CBs collected with NTD were significantly higher than those of the three CBs in PM_2.5,indicating that each component of the three CBs（CB,PCB,TCB）in ambient air are mainly distributed in the gas phase,with rarely distribution attached to fine particulate matter.