Application Of Novel Halloysite Nanotube Composites In The Detection Of Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons?PAHs?are composed of two or more benzene rings bonded at an angle arranged in a linear cluster.It is a ubiquitous pollutant in the environment and also accumulates in food during cooking and processing.It has a great impact on human life activities,so it is important to study the presence of trace levels of PAHs.Halloysite nanotubes?HNTs?are the only clay minerals that exist in the form of nanotubes,with different internal and external surface chemistry,which makes them easy to be modified into functional materials.In this paper,three new magnetic adsorbent materials were prepared based on HNTs.Magnetic solid-phase extraction?MSPE?combined with gas chromatography quadrupole mass spectrometry?GC/MS?was used for the qualitative and quantitative analysis of PAHs in food and the environment.The first chapter introduces the nature,sources,risks and sample pretreatment methods of PAHs.The structural characteristics of HNTs and the modification methods as well as their applications in the field of analytical chemistry were described briefly.Finally,the design ideas and research contents of this paper were elaborated.In the second chapter,chitosan?CS?functionalized magnetic halloysite nanotube?MHNTs?composite material?MHNTs@CS?was prepared for the determination of PAHs in environmental water samples.MHNTs loaded with Fe₃O₄ were synthesized by co-precipitation method under a nitrogen atmosphere,and then MHNTs were CS-functionalized with glutaraldehyde as a crosslinking agent to obtain MHNTs@CS.The synthesized materials were characterized by transmission electron microscopy?TEM?,Fourier transform infrared spectroscopy?FT-IR?,X-ray powder diffraction?XRD?,X-ray energy dispersion spectroscopy?EDS?,magnetic analysis?VSM?,and thermogravimetric analysis?TGA?.Factors affecting MSPE:MHNTs@CS dosage,sample solution pH,salt effect,etc.were investigated,and the optimal extraction conditions were obtained.Under this condition,a wider linear range was obtained.The correlation coefficients?R²?of the five PAHs of phenanthrene,anthracene,pyrene,benz[a]anthracene and chrysene were greater than 0.9967.LOD?0.41 ng/L and LOQ?1.53 ng/L,the relative standard deviations of intra-day precision and inter-day precision were less than 9.8%and 15.9%,respectively,and the spiked recoveries were between 62.5¹15.9%.In the third chapter,MHNTs composite materials?MHNTs@PDA?modified by polydopamine?PDA?were synthesized for the determination of PAHs in tea beverages.PDA can be self-polymerized on the surface of MHNTs to form MHNTs@PDA by pH induction under oxidizing conditions.The materials were characterized and the ideal structure was obtained.This adsorbent material was used for MSPE of PAHs,and the parameters affecting the extraction efficiency were explored,and compared with other materials.Under the optimal conditions,the six analytes of fluorene,phenanthrene,anthracene,pyrene,benz[a]anthracene and chrysene showed good linearity in the concentration range of 0.2⁵0?g/L.R²?0.9944.The ranges of LOD and LOQ were 0.023⁰.056?g/L and 0.077⁰.180?g/L.The spiked recovery was between 68.0 and 101.8%,and the proposed method has been successfully applied to the detection of PAHs in tea beverages.Chapter 4 synthesized polyaniline?PANI?modified MHNTs composite material?MHNTs@PANI?for the determination of PAHs in beer by MSPE/GC/MS.PANI is easy to polymerize and has good ion exchange,hydrogen bonding and hydrophilicity properties.Therefore,PANI-coated adsorbent materials were synthesized on the surface of MHNTs,and the materials were characterized.MHNTs@PANI was used to adsorb fluorene,phenanthrene,anthracene,pyrene,benz[a]anthracene and chrysene.The six analytes were detected by GC/MS to optimize the conditions affecting the extraction recovery.The method was evaluated under the optimum conditions.This method showed good linear behavior in the concentration range of 0.05¹00?g/L.R² ranged from 0.9962 to 0.9991.LOD and LOQ were1.64¹4.20 ng/L and 4.91⁴6.86 ng/L,respectively.The intra-day precision RSD was1.5⁷.4%,the intra-day precision RSD was 3.8⁹.4%,and the recovery was between78.8¹14.6%.