Preparation Of Zn ZnFe₂O₄ Based Materials And Their Applications In Sample Pretreatment

zinc ferrite（ZnFe₂O₄）can be used as environmentally friendly magnetic source in the process of sample pretreatment,due to their unique physicochemical properties,good stability,nontoxicity and excellent magnetism.In this paper,ZnFe₂O₄ microspheres,reduced graphene oxide/zinc ferrite（r GO/ZnFe₂O₄）and melamine based porous organic polymer/zinc ferrite（PTPA/ZnFe₂O₄）magnetic composites were prepared and applied to the enrichment of synthetic dyes、estrogens and bisphenols respectively1.In this work,ZnFe₂O₄ nanometer microspheres were prepared by the combination of solvothermal method and thermal treatment,and they were applied as an adsorbent for d-PT-SPE to enrich trace colourants from food samples.The optimal experimental parameters were obtained by investigating adsorption and desorption parameters respectively.Then under the optimum experimental conditions,the five synthetic colourants all showed good linear relationship in the range of 5-20000 ng/m L with the correlation coefficients（R2）between 0.9993 and 0.9999.The limits of detection（S/N = 3）were achieved at 2–7 ng/m L.Then three real samples were selected to verify this method,and their recoveries were in the range of 72.03 %-104.83 % with the RSD less than 6.89 %,indicating that the developed method was satisfied for selective enrichment and determination of trace colourants from complex food samples.2.Reduced graphene oxide/ZnFe₂O₄（r GO/ZnFe₂O₄）nanocomposite was facile prepared and applied as magnetic sorbent for the extraction of estrogens from water,soil,and fish samples prior to HPLC analysis.The adsorption and desorption parameters affecting the efficiency of magnetic solid-phase extraction（MSPE）were investigated.With the developed method,good linearity was observed in the range of 0.05-500 ng/m L with the correlation coefcients（R2）between 0.9978 and 0.9993.The limits of detection（S/N=3）and limits of quantifcation（S/N=10）were achieved at 0.01-0.02 ng/m L and 0.05 ng/m L,respectively.The enrichment factors were calculated as the range of 241-288.Using r GO/ZnFe₂O₄ nanocomposite as the sorbent,the developed MSPE followed by HPLC analysis,was applied to analysis of estrogens in river water,soil and fsh samples.The recoveries for four target estrogens were in the range of 71.23-104.60 % with RSDs less than 10.05 %.To further validate the results obtained from the developed HPLC-MSPE method,the extracted solution of water soil and fish samples with enrichment were further analyzed by UPLC-MS.The results showed that it is similar with the results obtained from the developed HPLC-MSPE method.In conclution,the method has the potential application in the extraction and preconcentration ultra trace compounds in complex matrices,such as environmental and biological samples.3.In this work,the magnetic nanocomposite of melamine based polyporous organic polymer/zinc ferrite（PTPA/ZnFe₂O₄）was firstly synthesized,and applied as magnetic sorbent for stir bar-sorptive dispersive microextraction（SBSDME）to extract bisphenols prior to HPLC analysis.The optimal experimental parameters were investigated and under the optimized conditions,the method was successfully validated showing good linearity in the range of 0.5-200 ng/m L with R2 ≥ 0.9952.The limits of quantifcation（S/N = 3）is between 0.5 and 0.75 ng/m L,and the limits of detection is 0.3-0.15 ng/m L.Then the method was applied to the detection of bisphenols in environmental and biological samples,and the recoveries of four bisphenols were in the range of 79.76 %-100.29 %,the results show that PTPA/ZnFe₂O₄ magnetic nanocomposite with good stability,high precision and reliability can be applied to the enrichment and detection of bisphenol.