Studies On Magnetic Solid-phase Extraction Based On Polystyrene-coated Magnetic Nanoparticles

With the development of various kinds of pretreatment techniques for complexmatrix, magnetic solid-phase extraction (MSPE) has attracted much interest in thefield of sample preparation recently. By combining the advantages of conventionalsolid phase extraction methodology and modern magnetic nano materials, MSPEshowed great superiority in the concentration of trace pollutants in complex liquidmatrix. Moreover, it was proved that most MSPE adsorbents can be reused after aneasy washing process. The MSPE should be more cost-saving, efficient andconvenient compared to other traditional extraction techniques. The exploitation ofvarious MSPE adsorbents and the application of MSPE are more and more importantfor their irreplaceable role in the detection of pollutants in environmental water andillegal additives in foodstuffs.Our work mainly concentrates on the study of magnetic solid-phase extractionbased on polystyrene-coated magnetic nanoparticles. There are three parts in thethesis:1. Preparation of polystyrene-coated magnetic nanoparticles (MNPs/PSt)The polystyrene-coated magnetic nanoparticles were prepared with a two-stepmethod which combines chemical coprecipitation and emulsion polymerization.Firstly, the Fe3O4MNPs coated with bilayer surfactants of oleic acid and sodiumdodecyl benzene sulfonate were prepared according to a modified coprecipitationmethod. This magnetite was washed and then dispersed in deionized water. Styreneand methacrylic acid were added and the mixture was stirred continuously under thenitrogen steam. The reaction system was heated to80℃and KPS was added toinitiate the polymerization. The characterization of the as-prepared MNP/PSt wascarried out based on FT-IR spectra, TEM images and maganetization curves.2. Extraction of pyrethroids residues in environmental water samples based onMSPEMSPE coupled with ultrafast liquid chromatography was applied for the detection of pyrethroids in environmental water samples. MNPs/PSt synthesized in our ownlaboratory were used as adsorbent for this MSPE. Extraction conditiuons wereoptimized. The limits of detection for lambda-cyhalothrin, deltamethrin, esfenvalerate,permethrin, bifenthrin were0.015,0.012,0.026,0.020,0.013ng mL-1, respectively.Recoveries obtained by analyzing spiked water samples at three concentration levelswere between78.97%and96.05%.3. Extraction of Sudan dyes in red wines, juices and mature vinegars based onMSPEBased on the previous work, MSPE was extended to the detection of illegaladditives in foods and drinks. Sudan dyes in red wines, juices and mature vinegarswere successfully extracted with satisfactory recoveries between76.3%and96.6%.The limits of detection for SudanⅠ, Sudan Ⅱ, Sudan Ⅲ and Sudan Ⅳwere0.0039,0.0063,0.0057and0.017ng mL-1, respectivel.