Application Of Magnetic Solid Phase Extraction Method Based On Functionalized Laponite In The Detection Of Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons（PAHs）are a type of persistent organic pollutants,which are highly toxicity,not easily degraded,and remain in the environment for a long time,which can cause great harm to the ecosystem and human health.The two main sources of PAHs contamination include environmental deposits and thermal processing of food.PAHs in the environment enter the human body through respiration or contact after being deposited.Foods also produce high levels of PAHs pollution during thermal processing（smoking,grilling,baking,and direct drying）.Therefore,the monitoring of PAHs in the environment and food has very important meaning.However,food and environmental samples have complex matrices,and it is crucial to choose an appropriate sample pretreatment method before performing instrumental analysis.In this thesis,three magnetic nanomaterials were prepared as magnetic solid phase extraction（MSPE）adsorbents combined gas chromatography-quadrupole mass spectrometry（GC-MS）to detect PAHs in environmental water samples,coffee,and tea soup samples.The thesis is as follows:Chapter 1:Briefly describes the properties,source and hazards of PAHs;Summarizes the sample pretreatment methods and detection methods of PAHs commonly used in recent years,which provides a direction for the selection of subsequent experimental methods;The properties,modification and application of laponite was introduced;Expounded the design thoughts and research content of this article.Chapter 2:Chitosan（CS）modified magnetic laponite（Lap@Fe₃O₄@CS）nanomaterial was prepared.Fourier transform infrared spectroscopy（FTIR）,transmission electron microscopy（TEM）,X-ray powder diffraction analysis（XRD）,Vibration sample magnetometer（VSM）and thermogravimetric analysis（TGA）are used to characterize the material.Lap@Fe₃O₄@CS has strong magnetic intensity and is easy to collect which greatly reduce experimental time.The influencing factors of the recoveries were explored.The linear range,limit of detection,limit of quantification,and spiked recoveries of the analytical method were verified.The results showed that the method has a wide linear range and a good linear relationship,and the correlation coefficient is between 0.9922 and 0.9991.The limit of detection is between 0.0008-0.1048μg/L,the spiked recovery is between 70.06-108.36%,RSD inter-day is below 5.8%,RSD intra-day is less than 6.5%.The method has good reproducibility and has been successfully used to detect PAHs in five environmental water samples.Chapter 3:Lap@Fe₃O₄@PANI adsorption material is synthesized by using polyaniline（PANI）coated magnetic laponite.The PANI coated on the surface of the material has the advantages of good environmental stability,low cost and large surface area.Theπ-πinteraction between PAHs molecules makes Lap@Fe₃O₄@PANI as a new material PAHs adsorption effectively.After being characterized by FTIR,TEM,XRD,VSM and TGA,Lap@Fe₃O₄@PANI is used for the magnetic solid phase extraction of PAHs.Optimization of extraction conditions makes MSPE faster.The established method has low limit of detection,ranging from 0.4594 to 16.304 ng/L,and the spiked recoveries are between 62.85%to95.83%.It has been successfully applied to the detection of PAHs in coffee.Chapter 4:Based on the in-situ self-polymerization of dopamine（DA）,the magnetic nanoparticles coated with polydopamine（PDA）were synthed,.The materials were characterized by FTIR,TEM,XRD,VSM and TGA.The adsorbent material shows good adsorption performance for eight kinds of PAHs,and achieves high-efficiency extraction of PAHs.Combined with GC/MS,the method was verified under the optimized conditions.The spiked recoveries are between 73.2-112.9%,the RSD were less than 8.7%,and the LOD were between 0.0025-0.0283μg/L.The method is applied to the detection of PAHs in tea soup.