Studies On Metal Organic Framework Membranes Based Solid Phase Extraction Of Environmental Estrogens

Environmental estrogens(EEs)are a group of endocrine disrupting chemicals with estrogenic effects,including natural estrogens such as estradiol,as well as synthetic exogenous such as bisphenol A.They can enter the human body via the food chain through ingestion of water and feed,and can also contaminate food by migrating from food contact materials.When accumulated in human body to a certain amount,EEs could interfere with endocrine causing teratogenesis and even trigger cancer.Therefore,it is of great significance to monitor the estrogen in the environment and food.It is essential to establish an effective preprocessing method to remove the interference and concentrate the analyte,due to the complexity of sample and the trace amounts of environmental estrogen.As a new type of adsorbent,metal organic frameworks(MOFs)are widely used in sample pretreatment due to their large specific surface area,adjustable pores,good stability and variety.Therefore,two novel membrane solid-phase extraction(SPE)methods were established with MOFs as adsorbent,and high-performance liquid chromatography-fluorescence detector(HPLC-FLD)was used as a quantitative method.Those methods boasts their great rapidness,accurate sensitivity as well as satisfied reliability for the detection of EEs in environmental and food.The main research contents and results are summarized as follows:(1)A novel SPE device,using MOFs as the adsorbent and nylon membrane in the disposable filter as the adsorbent carrier,was developed based on the MOF-deposited nylon membrane,combined with HPLC-FLD to detect estradiol(E2),estriol(E3)and estrone(E1)in water.Firstly,four kinds of MIL series MOFs were successfully prepared by hydrothermal synthesis,their structure,crystal forms and surface properties were characterized by X-ray diffraction(XRD),scanning electron microscope(SEM)and surface area analysis.Next,the integrity of the nylon membrane in the proposed SPE device was verified by simulating the solid phase extraction process.Finally,by optimizing the preparation process,adsorption and elution conditions of the new extraction device,three target EEs in 10 m L water sample could be adsorbed within 4 min and eluted within 1 min.There were good linear relationships between the range of 0.2?500 ?g/L for E2 and E3,and 5?500 ?g/L for E1,the limits of detection for three analytes were 0.05 ?g/L,0.06 ?g/L and 1.50 ?g/L,respectively.The recoveries for all targets at three spiked levels in real water samples ranged from 84.1% to 107.9%,and the relative standard deviations(RSDs)lower than 5.5%.In this method,nylon membrane and MOFs play a role of synergistic adsorption,and have the advantages of simple device,low cost,rapid,and high sensitivity.However,it is not suitable for large-volume,fatty and protein-rich samples.(2)In order to realize the pre-processing of large-volume and complex samples,the mixed matrix membrane of poly(vinylidene fluoride)doped with MIL-101(Cr)was prepared as a solid phase extraction adsorbent,and combined with HPLC-FLD to establish a detection method for bisphenol A(BPA)in milk and its packaging.The crystal form and structure of MIL-101(Cr)in the synthesized membrane and the thickness of membrane were characterized by XRD,SEM,Fourier transform infrared.The addition amount of MIL-101(Cr)during the preparation of membrane and adsorption,and the elution conditions during the extraction were optimized.Under the optimal conditions,the liner range of the development method was 0.1?50?g/L,and the limit of detection and limit of quantification were 0.016 ?g/L and 0.050 ?g/L,respectively.The membrane has good repeatability and reproducibility,and the extraction efficiency has no significant change after the membrane being reused for 20 times.The development method was applied to the detection of BPA in milk packaging and milk sample.BPA was detected in five different kind of milk packaging,the detected concentration was in the range of 0.23?0.56 ?g/g and the RSDs were less than 9.4%,the recoveries of milk packaging spiked in 2 levels were between 89.3%?110.6%.The recovery of real milk samples was between 74.2% and 94.1%,and the RSDs were less than 7.2%.The method is simple,sensitive and reproducible,and can be successfully applied to the quantitative analysis of BPA in milk and milk packaging.