Detection Of Polycyclic Aromatic Hydrocarbons And Nitrobenzene Pollutants In Environmental Samples By Solid-phase Microextraction Fiber Combined With Gas Chromatography

With the continuous progress and development of the society,people’s living standard has been significantly improved,but the environmental pollution problem has become increasingly serious.Pollutants in the environment are directly related to people’s health,so it is particularly important to establish a sensitive and accurate detection method to detect pollutants in the environment.Due to the matrix in environmental samples is relatively complex and the content of contaminants is generally low.So,it is necessary to pre-treat the samples before detection in order to separate and enrich the target analyte and reduce or eliminate the matrix interference.There are many kinds of sample pretreatment techniques,among which solid phase microextraction(SPME)is a new sample pretreatment technique which is simple to operate and does not need solvent.and it is easy to be combined with gas chromatography and other analytical instruments.The core of SPME technology is fiber coating.Although there have been some commercial fibers,but the extraction efficiency of these fibers is low and the price is expensive.Therefore,it is of great significance to study new fiber coating materials to improve the extraction ability of SPME technology.In this paper,on the basis of a large number of related literatures,three different adsorbent materials were successfully prepared.The material was coated on the stainless steel wire by physical adhesion or sol-gel technology to prepare the solid phase microextraction fibers.They have been successfully applied to extract organic pollutants(polycyclic aromatic hydrocarbons and nitrobenzene pollutants)from environmental samples(water and soil samples).The main research work is as follows:(1)In this study,in order to prevent the agglomeration of graphene from affecting its adsorption performance,boron nitride was used to modify graphene and successfully synthesized boron nitride modified reduced graphene oxide composite material.This material was used as an adsorbent and combined with solid phase microextraction technology to separate and enrich seven kinds of polycyclic aromatic hydrocarbons in water and soil samples,and then use gas chromatography-hydrogen flame ionization detector to detect them.Under optimal conditions,the linear response range of the analytes for water sample is 0.25-50 ng mL-1 with the correlation coefficients(r)ranging between 0.9953 and 0.9996.The linear range for soil sample is 1.0-400 ng g-1 with r ranging from 0.9959 to 0.9999.On the basis of the signal-to-noise ratio of 3,the limits of detections for the analytes ranged from 0.05 to 0.15 ng·mL-1 for water samples,and from 0.3 to 0.5 ng g-1 for soil samples.The relative recoveries of the seven polycyclic aromatic hydrocarbons for water and soil samples were in the range of 79.55-120.0%and 78.76-120.8%,respectively.The relative standard deviations for the determination of the analytes in water and soil samples were lower than 11%and 10%,respectively.The method is simple and suitable for the determination of polycyclic aromatic hydrocarbon residues in water and soil samples.(2)A conjugated microporous polymer(CMP)was synthesized by using 2,4.6-trihydroxy-1,3,5-phenyltriformaldehyde(TP)and hydrazine hydrate as monomers in the presence of a template.The synthesis conditions such as the type of template,the proportion of template.reaction temperature and reaction time were optimized.The synthetic CMP was coated on the stainless steel wire by sol-gel technique and used as solid phase microextraction fiber to extract nitrobenzene organic pollutants in environmental water and soil samples.Under optimal extraction conditions,the linear range of the method in water samples is 0.5-300 ng mL-1.the correlation coefficient(r)is between 0.9957 and 0.9997,and the limits of detection(LODs)are between 0.10-0.30 ng mL-1 at a signal-to-noise ratio of 3.In soil samples,the linear range was 10.0-3000 ng g-1,r was in the range of 0.9960-0.9998.and LODs were in the range of 3.0-6.0 ng g-1.The recoveries of 11 nitrobenzene compounds in 4 water samples and 3 soil samples were 80.00-121.0%and 80.43-120.1%,respectively.with RSDs less than 11%and 13%,respectively.(3)In this work,a covalent organic framework modified graphitic carbon nitride(g-C3N4@TpBD)was synthesized by modifying the graphitic carbon nitride(g-C3N4)with a covalent organic framework(COF-TpBD).The synthesis conditions including the mass ratio between g-C3N4 and benzidine(BD),solvent type,reaction temperature and reaction time were optimized.Under the optimal synthetic conditions,a novel spiny dendritic g-C3N4@TpBD adsorbent was obtained.The g-C3N4@TpBD was then coated on stainless-steel wire by sol-gel technique and used for the solid phase microextraction(SPME)of polycyclic aromatic hydrocarbons(PAHs)prior to gas chromatography mass spectrometer(GC-MS)detection.The established method was successfully applied to determine eight PAHs in six environmental water samples.Under the optimal extraction conditions,a wide linear range was obtained from 0.06 to 60.0 ng mL-1 with the correlation coefficients(r)varying from 0.9989 to 0.9999,and the limits of detection(LODs,S/N＝3)ranged from 0.02 to 0.05 ng mL-1.The relative recoveries(R)of the analytes for the six environmental water samples at the spiked concentrations of 0.5,3.0 and 30.0 ng mL-1 were between 83.6%and 118%with the relative standard deviations(RSDs)ranging from 2.4%to 11.3%.