Preparation Of Porous Organic Polymers And Their Applications In The Determination Of Organic Contaminants In Food Samples

The pesticide residues in agricultural products and the sanitary problems in the processing and storage of agricultural products such as dissolution of harmful substances in food packaging,have been seriously threatening human’s life and health.Therefore,it is very important to monitor the contents of harmful chemicals in food products.At present,chromatographic analysis is still the main method for accurate analysis and detection of pesticide residues and harmful substances.However,it is difficult to determine the analytes directly for real samples because of the low content of target analytes and complex sample matrix.Therefore,sample pretreatment is an indispensable step in the analysis process.Solid phase extraction(SPE)and magnetic solid phase extraction(MSPE)have been widely used in the analysis of food and environmental samples due to their advantages of high extraction efficiency,good reproducibility,simple operation and environmental friendliness.The key factor affecting the extraction performance of these two sample pretreatment techniques is the type of adsorbent.Therefore,developing adsorbents with stable properties,high selectivity and high extraction ability is highly desirable.In this paper,several new methods for the determination of some organic pollutants in food and environmental samples were developed on the basis of either SPE or MSPE and high performance liquid chromatography(HPLC).After a thorough study of relevant literatures and experimental investigations,some achievements were made.The main work of this dissertation includes:(1)Benzoxazine porous organic polymer was used as SPE adsorbent for chlorophenol enrichment in water and honey samples.A benzoxazine porous organic polymer(BoxPOP)constructed from p-phenylenediamine,phloroglucinol and paraformaldehyde was fabricated and explored as an adsorbent for solid-phase extraction(SPE)of four chlorophenols(CPs)from water and honey samples.Under the optimized SPE conditions,the response linearity for the analysis of the SPE extract of the chlorophenols by high performance liquid chromatography-diode array detector was observed in the range of 0.2～40.0 ng/mL for water samples and 5.0～400.0 ng/g for honey samples.The method detection limits of the analytes were 0.06～0.08 ng/mL for water samples and 1.5～2.0 ng/g for honey samples.The recoveries of the analytes from fortified water and honey samples ranged from 84.8%to 119.0%with the relative standard deviations(RSDs)below 8.4%.The results indicate that the prepared BoxPOP is an effective adsorbent for CPs.The established method provides an alternative approach for the determination of CPs in real samples.(2)Chlorophenols in water and honey-pomelo beverage samples were enrichmented by phenylboronic-based hypercrosslinked polymers.Four new HCPs with phenylboronic acid(PBA),1,4-benzenediboronic acid,4-hydroxyphenylboronic acid and 4carboxyphenylboronic acid as the respective monomers were prepared for the first time.Their Brunner-Emmet-Teller surface areas were 909.1 m2/g,71.9 m2/g,39.8 m2/g and 29.3 m2/g,respectively.The prepared HCP with PBA as monomer(named as PBA-HCP)displayed the best adsorption capability for CPs.Then,it was investigated as a SPE adsorbent for the extraction of CPs from water and honey-pomelo beverage samples prior to HPLC with diode array detection.The established method had low limits of detection(LODs)for the analytes in the range of 0.06～0.2 ng/mL for water samples and between 0.3 and 1.0 ng/mL for honey-pomelo samples.The linear response for the analytes was in the range of 0.18～100.0 ng/mL for water samples and 0.9～100.0 ng/mL for honey-pomelo samples.The method also had a good repeatability with the RSDs less than 7.1%and a fairly good accuracy with the method recoveries falling between 80.0%and 120.0%.The adsorption capacities of the PBA-HCP for 2-chlorophenol,3-chlorophenol,2,3-dichlorophenol and 2,4dichlorophenol were 21.7 mg/g,31.2 mg/g,77.1 mg/g and 82.1 mg/g,respectively.The PBA-HCP also exhibited excellent extraction capabilities for many other compounds,especially for those with more hydrogen bonding sites.(3)A phenyl hypercrosslinked polymer(PHCP)was used as SPE adsorbent for phenylurea herbicides(PUHs)from radish samples.PHCP with a conjugated structure was synthesized by Friedel-Crafts alkylation reaction with benzene as monomer and p-methoxybenzene as crosslinking agent.Then,a PHCP-based SPE method combined with HPLC for analyzing PUHs in white radish samples was established.In the concentration range of 1.5 to 100.0 ng/g,the analytes for white radish samples have a good linear relationship between the concentration and signal.The linear correlation coefficient(r)is in the range of 0.9969 to 0.9990.The LODs ranged from 0.5 to 0.8 ng/g,and the limits of quantification(LOQs)are between 1.5 and 2.4 ng/g.The RSDs are in the range of 3.0%and 5.0%.This method has high accuracy and precision,and provides a new approach for the detection of PUHs in actual samples.(4)Magnetic phenyl-based hypercrosslinked polymer(M-PHCP)was used as MSPE sorbent for extraction and analysis of phthalate esters(PAEs)plasticizers in beverages.Fe3O4@SiO2 was modified by phenyl triethoxysilane and a core-shell magnetic composite material M-PHCP was synthesized by Friedel-Crafts alkylation reaction.The M-PHCP was characterized by SEM,TEM,BET,XRD,etc.A sensitive and accurate analytical method for the determination of PAEs plasticizers in bottled vitamin water beverages was established with M-PHCP as the adsorbent for MSPE.This method has a good linear relationship in the concentration range of 0.5 to 100.0 ng/mL,and r is between 0.9962 and 0.9980.The LODs are in the range of 0.15～0.3 ng/mL.(5)The neonicotinoid insecticides were determined in water and honey samples with covalent organic framework combined.A uniform spherical structure covalent organic framework(TAPA-BPDA-COF)was prepared by a facile method at room temperature with tris(4-aminophenyl)amine(TAPA)and 4,4’-biphenyldicarboxaldehyde(BPDA)as building blocks.The structure of TAPA-BPDA-COF was characterized by various techniques.Based on SPE with the TAPA-BPDA-COF as the sorbent and HPLC-DAD detection,a sensitive analytical method was established for the determination of four neonicotinoid insecticides from water and honey samples.Under the optimum conditions,good linear response for the quantification of the analytes was achieved in the range of 0.3～50.0 ng/mL for water samples and in the range of 8.0～500.0 ng/g for honey samples.The method recoveries fell in the range of 80.0%一 121.9%with RSDs less than 7.6%.The LODs at the signal to noise ratio of 3 were measured to be in the range of 0.08～0.12 ng/mL for water samples and 2.6～3.3 ng/g for honey samples,depending on compounds.(6)Magnetic composite HCPs were used as adsorbents for the extraction and analysis of nitroimidazole fungicides in water and milk samples.A series of HCPs was synthesized by one-step Friedel-Crafts alkylation reaction with benzene and PBA as monomers,dimethoxymethane as crosslinking agent,dichloroethane as solvent and ferric chloride as catalyst.A series of magnetic HCPs composite(COOH-Fe3O4@HCPs)with different COOH-Fe3O4 ratios were prepared by hydrothermal method.COOH-Fe3O4@HCPs with 40%COOH-Fe3O4 was selected as adsorbent for MSPE prior to the determination of nitroimidazoles in water and milk samples.The LODs of the nitroimidazoles in water samples were 0.03～0.2 ng/mL,and the linear range was 0.1～100.0 ng/mL with r higher than 0.9995.The LODs for milk samples were 0.2～0.5 ng/mL,the linear range was 0.7～100.0 ng/mL,and r was between 0.99861 and 0.99998.The adsorption mechanism between the adsorbent and the target analytes were studied.The results showed that the hydrogen bond was the main force between the nitroimidazole and COOH-Fe3O4@HCPs.The study showed that the adsorbent had high adsorption performance toward the organic pollutants with more hydrogen bonds.