The Application Of Functionalized Magnetic Nanoparticles Based On Polydopamine In Sample Pretreatment

Magnetic nanoparticles(MNPs)are used as sorbents in the magnetic solid phase extraction(MSPE).Compared to traditional SPE sorbents,magnetic nanoparticles possess large surface area and short diffusion route,which may result in high extraction efficiency with shorter time.In order to selectively adsorb the target molecule,the modification of MNPs with a suitable coating has been proven to be one of the most efficient approaches.As a new method for modification,polydopamine(PDA)coating provides a variety of functional groups which can interact with analytes and be further modified if necessary.So it can be used in the preparation of multifunctional nanocomposites for the purpose of enrichment and analysis.The thesis mainly includes the following three parts:In chapter 1,the developments of MSPE were introduced.Different functionalized magnetic nanoparticle materials used in MSPE and the applications of PDA coating in chromatography analysis were reviewed.In chapter 2,PDA coated Fe3O4 nanoparticles(Fe3O4 @ PDA NPs)were prepared as highly efficient adsorbents by a simple procedure.The MSPE method for the extraction and enrichment of four representative synthetic colorants prior to high performance liquid chromatography analysis was introduced.Fe3O4@PDA NPs were characterized by using transmission electron microscopy(TEM),X-ray diffraction(XRD)and Zeta potential analysis.Several factors affecting the extraction efficiency,mainly including the pH of the sample solution,the amount of adsorbent,extraction time and the desorption conditions,were systematically studied.Under the optimized conditions,the enrichment factors for the four colorants were both higher than 176.When used for quantitative analysis,wide linearity ranges(1~500 ?g L-1 for amaranth and Ponceau 4R,and 0.80~500 ?g L-1 for sunset yellow and allure red)were achieved with good correlation(R2? 0.9995).The limits of detection(LODs)for the established d-SPE-HPLC method were found to be 0.20~0.25 ?g L-1,which were lower than most chromatographic methods previously reported for synthetic colorant analysis.The developed method was also successfully applied to the analysis of colorants in beverage samples with satisfactory results,demonstrating its reliability and feasibility in real sample analysis.In chapter 3,PDA coating was used as reducing and immobilizing agents simultaneously to deposit Au NPs on PDA modified Fe3O4 NPs directly.The synthesized products were characterized by TEM and magnetic properties test system.When the pH,temperature of reaction solution,and the amount of chloroauric acid were changed,the Au NPs with different particle sizes were obtained.The method is simple and can avoid the use of additional reducing agent with toxicity.Fe3O4@PDA NPs synthesized here were used in adsorption for steroids.