Extraction And Enrichment Of Some Organic Pollutants From Food And Environmental Samples With Cross-linked Polymer As Adsorbent

The low concentrations and complex matrices encountered in real samples dictate the need for separation and preconcentration steps before high performance liquid chromatographic analysis.Solid phase extraction?SPE?and magnetic solid phase extraction?MSPE?were common sample preparation procedures and the adsorbent plays a vital role in the SPE and MSPE method.Therefore the development of effective adsorbents is necessary for its wider applications.In this work,various crosslinked compounds were prepared by selecting appropriate chemical agent as a cross-linker,such as phytic acid induced three-dimensional graphene,magnetic?-cyclodextrin polymer,hypercrosslinked triphenylamine networks.These materials were used as the adsorbent for the extraction of phthalate esters,carbamates,benzoylurea insecticides,phenylurea herbicides from food samples before highperformance liquid chromatographic analysis.Thesis is mainly concerned with the following aspects:1.A three-dimensional graphene was synthesized through a hydrothermal reaction of graphene oxide with phytic acid.The microstructure and morphology of the phytic acid induced three-dimensional graphene were investigated by nitrogen adsorption–desorption isotherms,transmission electron microscopy and scanning electron microscopy.With a large surface area and three-dimensional structure,the graphene was used as the solid-phase extraction adsorbent for the extraction of phthalate esters from bottled water and sports beverage samples before highperformance liquid chromatographic analysis.The results indicated that the graphene was efficient for the solid-phase extraction of phthalate esters.The limits of detection?S/N=3?of the method for the analytes were 0.02⁰.03ng/mL for the water samples and 0.03⁰.15 ng/mL for the sports beverage sample.The limits of quantitation?S/N=9?for the analytes were 0.06⁰.09 ng/mL for water samples and 0.09⁰.45 ng/mL for sports beverage sample.The calibration curves for the phthalate esters by the method had a good linearity from 0.1 to 80.0 ng/mL with correlation coefficients larger than 0.9997.The recoveries of the analytes for the method fell in the range of 86.7%¹16.2%with the relative standard deviations between 1.5%and 6.8%.2.A nanocomposite?designated as PAG?possessing amphiphilic properties was prepared by a single-step method from graphene oxide and phytic acid,in which phytic acid acts as both an inducer and cross-linking agent.The morphology and microstructure of PAG were characterized by nitrogen adsorption,scanning electron microscopy and transmission electron microscopy.The PAG possess a 3 dimensional network structure with interpenetrated nano-and micropores and represent a viable adsorbent for solid-phase extraction of carbamates pesticides prior to their quantitation by high performance liquid chromatography.Under optimum conditions,the calibration plot is linear in the 0.5 to 80ng/g concentration range in case of apple samples,and in the 1.0 to 80 ng/mL range for juice samples.The respective limits of detection?for S/N=3?are between 0.05 and 0.1ng/g,and between 0.2 and 0.3 ng/mL.The PAG has a high adsorption capability,and in our preception it may become a useful adsorbent for the preconcentration of other organic pollutants.3.A magnetic?-cyclodextrin polymer was successfully prepared and used as an adsorbent for the magnetic solid-phase extraction of six benzoylurea insecticides?diflubenzuron,triflumuron,hexaflumuron,teflubenzuron,flufenoxuron,and chlorfluazuron?from honey,tomato,and environmental water samples.The influence of the main experimental conditions on the extraction was studied.Under the optimized conditions,the?-cyclodextrin polymer@Fe₃O₄ showed an excellent extraction performance for the benzoylurea insecticides.A good linearity was obtained for the analytes in the range of 3.0⁸00 ng/g for honey samples,0.3¹60 ng/g for tomato samples,and 0.1⁸0.0 ng/mL for water samples,with the correlation coefficients above0.9998.Satisfactory repeatabilities were achieved,with the relative standard deviations less than 5.7%.The limits of detection?S/N=3?of the method for the benzoylurea insecticides were 0.2⁰.8 ng/g for honey samples,0.04⁰.10 ng/g for tomato samples,and 0.02⁰.05 ng/mL for water samples.The method was successfully used for the determination of the six benzoylurea insecticides residues in honey,tomato,and environmental water samples with a satisfactory result.4.A hypercrosslinked triphenylamine polymer?HCTPA?was prepared through a simple one-step Friedel-Crafts alkylation reaction.The HCTPA had an extended?-conjugated system,large specific surface areaand high micropore volume.In order to evaluate its extraction performance,the HCTPA was used as theadsorbent for the solid-phase extraction of the phenylurea herbicides?monuron,chlortoluron,isopro-turon,monolinuron and buturon?from watermelon,tomato and cucumber samples.The main parametersthat could affect the extraction efficiency including the sample volume,sample solution pH,samplesolution loading rate and desorption conditions were investigated and optimized.Under the optimizedconditions,the HCTPA showed a good extraction performance for the target analytes.The linear range for the quantification of the analytes was in the range of0.4¹60.0 ng/g with the correlation coefficients of 0.9996⁰.9999.The limits of detection?S/N=3?of the analytes by the method ranged from 0.06 to 0.12 ng/g for watermelon and tomato,and 0.06⁰.15 ng/g for cucumber samples.The recoveries of the analytes for the method were between 83.1%and 112.5%with the relative standard deviations below 5.5%.These results indicate that the HCTPA can be used for the enrichment of phenylurea herbicides from complex matrix samples like watermelon,tomato and cucumbers.