Preparation Of Functionalized Magnetic Polyamide-amine Dendrimers And Their Application In Environmental Analysis

Due to the discharge of industrial,agricultural and human domestic wastewaters,the types and concentrations of pollutants in the water environment are increasing year by year.The typical pollutants in water environment are polycyclic aromatic hydrocarbons(PAHs),heterocyclic aromatic hydrocarbons,heavy metal ions and bisphenols,etc.They will put great threat to human health.PAHs and heterocyclic aromatic hydrocarbons are carcinogenic and teratogenic.Heavy metal ions have properties of bioaccumulation,high risk,and difficult degradation.Bisphenolic compounds are typical endocrine disruptors,which have neurotoxicity,genotoxicity,and reproductive toxicity.Therefore,it is very important to develop simple,efficient and sensitive methods for detecting such pollutants.However,the concentration of pollutants in environmental waters is usually at trace level and the matrix of environmental waters is very complex,so it is difficult to directly detect pollutants in water samples.Hence reliable sample pretreatment technologies are required to enrich,separate and purify the samples for achieving accurately quantitative analysis.In recent years,the development of sample preparation technologies has attracted extensive attention,and a variety of efficient pretreatment technologies have been established and employed in many fields.Among them,magnetic solid phase extraction(MSPE)is a new type of sample pretreatment technology with merits such as simple operation,high enrichment factor and easy separation,which is widely used in the field of environmental sample preparation.The adsorbent is the key factor of MSPE,and development of functional magnetic adsorbents is one of the current research hotspots.In this thesis,four functionalized magnetic polyamide-amine dendrimer composite materials were designed and prepared based on the structure and properties of polyamide-amine dendrimer and magnetic materials.In combination with high performance liquid chromatography(HPLC)and gas chromatography-tandem mass spectrometry(GC-MS)and MSPE,new methods for efficient enrichment and sensitive detection of typical pollutants in environmental waters were established,and the adsorption mechanisms were explored.This thesis was divided into four chapters as follows:Chapter 1: A review was presented on the structure,properties,preparation methods and application in pollutants adsorption,biological imaging,protein immobilization and gene delivery of magnetic polyamide-amine dendrimer(MNPs@PAMAM).Chapter 2: By amidation reaction,4-mercaptobenzoic acid(4-MBA)was successfully modified onto magnetic polyamide-amine dendrimer(MNPs@PAMAM@4-MBA).MNPs@PAMAM@4-MBA was employed for adsorption and enrichment of phenanthrene,anthracene,fluoranthene,pyrene and benzo(a)pyrene from the environmental waters.The factors affecting MSPE were optimized,the adsorption kinetics and adsorption mechanism of five PAHs were investigated.The results showed that the adsorption of five PAHs followed pseudo-second-order kinetic model and Freundlich adsorption isotherm model.The targets had good linearity in the range of 0.1-300 μg/L,and limits of detection were in the range of 0.014-0.055 μg/L.The proposed method was applied to the detection of five targets in real water samples,and the spiked recoveries were in the range of 92.2%-98.6%.These results indicated that MNPs@PAMAM@4-MBA was an excellent magnetic functional material with good adsorption property and could be used for the enrichment of trace PAHs in environmental waters,which provided a good and powerful analytical platform for the enrichment and detection of trace PAHs in environmental waters.Chapter 3: Based on the excellent structure and properties of graphene oxide(GO),magnetic nanocomposite material(MNPs@PAMAM@GO)was prepared by amidation reaction.Utilizing MNPs@PAMAM@GO as an adsorbent,a new method was developed for the simultaneous enrichment of 7-methylquinoline,carbazole,9-methylcarbazole,dibenzothiophene,4,6-dimethyldibenzothiophene,anthracene,pyrene and fluoranthracene in environmental waters.Under optimal experimental conditions,the adsorption mechanism of eight targets were investigated.The adsorption of eight targets can be attributed to π-π conjugation,hydrophobic interaction and hydrogen bonding.MNPs@PAMAM@GO was a highly stable and recyclable magnetic material with good adsorption performance for heterocyclic aromatic hydrocarbons and PAHs.Chapter 4: L-Cysteine(L-Cys)has sulfhydryl,carboxyl,and amino groups,which is a polyfunctional compound.Herein,L-Cysteine was modified onto MNPs@PAMAM by amidation reaction.According to the principle that heavy metal ions can be complexed with sulfhydryl groups and amino groups,a simple and sensitive MSPE-HPLC method utilizing MNPs@PAMAM@L-Cys as adsorbents was established for Cd(II),Pb(II),Co(II)and Hg(II)in environmental waters.Under optimal experimental conditions,the adsorption mechanism of four heavy metal ions was investigated.The maximum adsorption capacities of Cd(II),Pb(II),Co(II)and Hg(II)were 116.20 μg/g,103.42μg/g,114.97 μg/g,117.79 μg/g,respectively.The limits of detection were 0.018 μg/L,0.014 μg/L,0.013 μg/L and 0.025 μg/L,respectively.The developed method with good selectivity and sensitivity can be used as a crucial alternative for the analysis of heavy metal ions in water environment.Chapter 5: β-cyclodextrin(β-CD)with hydrophilic outer surface functional groups and hydrophobic inner cavity structure was used to modify MNPs@PAMAM,which was noted as MNPs@PAMAM@β-CD.The synthetic composites were used as adsorbents of MSPE,a reliable analytical method was developed for sensitive detection of bisphenol S,bisphenol A,tetrabromobisphenol A,bisphenol AF and bisphenol AP in beverages.The factors affecting MSPE were optimized,the adsorption kinetics and adsorption mechanism of five BPs were studied.The results showed that the adsorption of five bisphenolic followed pseudo-second-order kinetic model and Langmuir adsorption isotherm model.The maximum adsorption capacities of five bisphenols were in the range of 131.80-157.08 μg/g.The results demonstrated that the developed method possessed low detection limits(0.016-0.039 μg/L),good reproducibility(RSD<2.42%)and strong practicability,and provided a robust optional technology for the detection of trace bisphenolic compounds.