| In recent years, strong carcinogenic organic pollutants has raised great pollution environmentand received widespread attention. They have many kinds, including the12kinds of persistentorganic pollutants (POPs) which were defined on the "Persistent Organic Pollutants StockholmConvention". They are toxic, persistent in environment and can accumulation through the foodchain, also they have the ability to migrate long distances, so although their are low concentrationsin the environment, they can be enriched through the food chain and can cause great harms tohuman beings through the bioaccumulation of the food chain, so it could be of great importance todetect PCBs at the ultratrace levels.Magnetic dispersive solid phase extraction (MDSPE) is a new sample pre-treatmenttechnology that was developed from the dispersive solid phase extraction (DSPE) method. InMDSPE, the adsorbent was dispersed in solution to adsorbed target molecule directly, this canincrease the contact area between the adsorbent and the molecule, improving the adsorptionefficiency. Also the existence of the magnetic material reducing the separation time, for it can beseparate easily by an external magnetic field. The key to MDSPE is to reduce the matrixinterference, therefore improving the selectivity of adsorbing materials is important. Carbonnanomaterials has large specific surface area and can adsorb organic compounds which hasbenzene ring structure through π-π stacking effect. It also has high absorption efficiency, largecapacity, in good thermal stability and chemical stability, it has been widely used this years.However, the adsorptive properties of carbon nanomaterials apply to all compounds that contain abenzene ring form the complex samples, the adsorption was physical and non-selective. Toovercome this limitation, this article has combined the advantages of magnetic molecularimprinting and carbon nanomaterials to synthesize a novel magnetic molecularly imprintedmaterials. They not only have strong enrichment capacity and high selectivity, but also can beseparated easily through an external magnetic field, avoiding the complicated centrifugationprocedure, enhancing the specificity, simplifying the whole adsorption process and reducing thematrix interference. The adsorbent was used for practical sample detection. Chapter one This chapter developed a simple, fast and sensitive electrochemiluminescence(ECL) method for detecting3,4-DCA at ultratrace levels. This method has not been usedpreviously for3,4-DCA detection, and is based on a96-well micro-plate modified withmolecularly imprinted sol-gel films combined with multi-walled carbon nanotubes (MIF-MWCNTs). Then the factors that can effect absorption efficiency has been optimized, includingthe detect condition of ECL, the dosage of MWCNTs, the adsorption time, etc, and alsocharacterize the material. In this experiment, we have compared the enrichment capacity of MIF-MWCNTs to non-molecularly imprinted sol-gel films combined with multi-walled carbonnanotubes (NIF-MWCNTs) and MIF, results showed that MIF-MWCNTs have a large adsorptioncapacity, high adsorptive selectivity and can be used for the selective enrichment of3,4-DCA. Thelinear range was from4×10-11to6×10-9mol L-1, with a low detection limit (LOD) of1×10-11molL-1. The detection sensitivity of the present method is higher than those of the most commonly usedchromatography methods, with the recovery of3,4-DCA from spiked samples of water rangingfrom83.3to110.5%. Thermodynamic analysis showed that the adsorption of3,4-DCA by theMIF-MWCNTs occurred spontaneously as an exothermic and entropy decreasing process (ΔH=-32.49kJ mol-1, ΔS=-117.89J mol-1). Kinetic equation fitting demonstrated that the adsorption of3,4-DCA could be fitted by an intraparticle diffusion model, and that the adsorption isotherm datafitted the Freundlich model.Chapter two Novel multi-wall carbon nanotube modified dummy-template molecularlyimprinted microspheres (MWCNTs@DMMIPs) were successfully synthesized as adsorbents forsix kinds of polychlorinated biphenyls (PCBs). In the polymerization process, the competitivematerial of PCBs in ELISA method,3,4-dichlorobenzene acetic acid (DCP), was used as a dummytemplate instead of PCBs, avoiding the leak of template molecule and can form hydrogen bondwith functional monomer in synthesis process. MWCNTs@DMMIPs were prepared by a surfacemolecular imprinting technique. The factors that can effect absorption efficiency has beenoptimized, including the kind and the dosage of elution solvent, the adsorption time, etc, and theadsorption materials were characterized by various kinds of characterization method. Wecompared the absorption efficiency of MWCNTs@DMMIPs with (multi-wall carbon nanotubemodified non-imprinted microspheres) MWCNTs@DMNIPs,(magnetic molecularly imprintedpolymer) MMIPs and MWCNTs, results showed that MWCNTs@DMMIPs exhibited goodselectivity and high adsorption efficiency for extracting PCBs. The materials were successfullyapplied to magnetic disperse solid phase extraction of six kinds of PCBs, followed by GC-MSdetermination in fish samples, the linear range was from0.16to100μg L-1, LODs of six kinds ofPCBs were0.0028-0.0068μg L-1and piked recoveries ranged between73.41-114.21%. Adsorption kinetics fit well with pseudo-second-order kinetic equation and also exhibited a3-stage intra-particle diffusion model. The Freundlich model was used to describe the adsorption isotherms.Chapter three The novel reductive graphene oxide-based magnetic molecularly imprinted poly(ethylene-covinyl alcohol)(EVAL) polymers (rGO@MMIPs) were one pot synthesised for the selective enrichment of six kinds of polychlorinated biphenyls (PCBs) in fish samples. In the experiment process the EVAL was adopted as the imprinted polymers, instead of functional monomer and cross-linker in traditional molecularly imprinted polymer. In this experiment, rGO@MMIPs were prepared by a surface molecular imprinting technique and3,3-dichlorobenzidine, the structural analogues of PCBs, was employed as dummy molecular, avoiding the leak of template molecule and can form hydrogen bond with functional monomer in synthesis process. The morphology and inner structure of the magnetic adsorbent were characterized by TEM, SEM, XRD, VSM, ect. Then the adsorbent was employed for magnetic disperse solid phase extraction (MDSPE) towards PCBs and exhibited good selectivity and high adsorption efficiency, followed by gas chromatography-mass spectrometry (GC-MS) determination in fish samples, the liner range of six kinds of PCBs was from0.11-100μg L-1, LODs were from0.007to0.014μgL-1and LOQs were0.007-0.014μg L-1. The piked recoveries of pratical samples were between78.90to93.73%. The material can be used for more than19times. Adsorption kinetics fit well with pseudo-first-order kinetic equation and the Freundlich model was used to describe the adsorption isotherms. |
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