Functionalization Modification Of Magnetic Polypropyleneimine Dendrimers And Their Applications For Enrichment And Detection Of Typical Environmental Pollutants

With the development of science and technology,pesticides,azo dyes and dye precursors,and UV filters and so on have been widely used,and enter into the environment by various ways and pose a serious threat to the environment.Therefore,it is of great significance to establish highly effective enrichment and detection methods for pesticides,azo compounds and UV protective agents in environmental water samples.Magnetic solid-phase extraction technology（MSPE）has been widely used due to its advantages of simple operation,less consumption of organic solvent,and reusability.However,due to the variety,complex structure and different properties of pollutants,the application of unmodified magnetic nanoparticles（MNPs）is limited to a certain extent.Functional surface modification of MNPs can significantly expand its application scope.For example,nanomaterials such as carbon nanotubes,graphene oxide,silica,and metal-organic frameworks have been successfully modified onto magnetic nanoparticles,and the series of synthesized new magnetic materials earned high enrichment efficiency,and achieved great applications.Dendrimers are synthetic macromolecules with a highly branched three-dimensional nanoscale structure,possess abundant of terminal functional groups,and can be modified with various functional groups to provide abundant of adsorption sites.Surface-modified dendrimers can be modified by designing based on the chemical and physical properties of the target pollutants in order to improve their adsorption performance or adsorption capacity.It will be of great research significance to combine the excellent properties of magnetic materials and the merits of the functional dendrimers for synthesizing magnetic dendrimer composites.In this thesis,magnetic materials were decorated with polypropyleneimine dendrimer（PPI）,and then the achieved magnetic materials were modified with C₆₀,β-CD and covalent organic framework（COF）,respectively.These materials were utilized to establish new methods for the detection of pyrethrin insecticides,azo compounds and UV filters in environmental water based on magnetic solid phase extraction in combination with GC-MS/MS,respectively.The thesis included three parts:（1）The magnetic nanomaterial(MNPs-PPI-Gn-C₆₀)was designed and synthesized.Its morphology and structure were characterized by Transmission electron microscope（TEM）and Raman spectroscopy,etc.It was used as the adsorbent in the MSPE process,and an MSPE-GC-MS/MS method for the enrichment and detection of eight kinds of pyrethroid pesticides was established.Under optimal conditions,the detection limits of the eight pyrethroids were in the range of 0.1-1 ng/L,the inter-day precisions were in the range of 1.9-4.4%,and the spiked recoveries in real samples were satisfied in the range of 86.6%-106.1%.（2）β-cyclodextrin（β-CD）was modified on the surface of magnetic polypropyleneimine dendrimer to obtain a new magnetic adsorbent MNPs-PPI-Gn-β-CD.Using the photoresponse mechanism of azo compounds and principle of MSPE,a novel MSPE-GC-MS/MS method was developed for enrichment and detection of azo compounds in environmental water samples including azobenzene,p-aminoazobenzene,p-diaminoazobenzene,o-aminoazotolueneand4-diethylaminoazobenzene.Under optimized experimental conditions,the detection limits of five azo compounds ranged from 0.1 to 0.5 ng/L,the intra-day precisions ranged from 2.0 to 4.6%,and the inter-day precisions ranged from 1.4 to 4.9%.The developed method was validated with the real water samples and satisfied results were achieved.（3）A covalent organic framework material modified magnetic polypropyleneimine dendrimer（MNPs-PPI-Gn-Tb Bd）was designed and synthesized using1,3,5-trismellitaldehyde（Tb）and benzidine（Bd）.The obtained MNPs-PPI-Gn-Tb Bd was a good adsorbent,and an effective method was constructed based on MSPE combined with GC-MS/MS for enrichment and detection of phenyl salicylate,oxybenzone,etocrylene and octocrylene in environmental water samples.Under the best experimental conditions,the linear ranges of octocrylene,etocrylene,phenyl salicylate and UV-9 were in the range of 0.01-20μg/L,0.05-20μg/L,0.04-40μg/L and 0.04-30μg/L,respectively.The detection limits of the four UV filters were in the range of0.01-0.04μg/L,and the intra-day precisions and inter-day precision were 1.7%-3.3%and 3.0-4.8%,respectively.The spiked recoveries of environmental water samples were very good in the range of 81.6%-93.0%.