Preparation And Application Of Molecularly Imprinted Silica Nanospheres Of Bisphenol A

Bisphenol A, known as BPA, is a chemical substance widely used in industry as a monomer in the production of epoxy resins and polycarbonates, and as an antioxidant in PVC plastics. As an important endocrine disrupting chemical that has estrogenic activity, monitoring of BPA has been giving rise to international concern.Molecular imprinted technology is based on the molecular recognition theory, and its main procedure is to synthesize molecular imprinted polymers(MIPs), which can selectively recognize a particular molecule or a family of structurally-related compounds to molecule. MIPs are also named artificial antibody and hold additional advantages over natural antibody, such as stability, ease of preparation, low cost, and reusability have led to their wide application in chromatography, catalysis, chemical sensors, and solid-phase extraction. In complex samples pretreatment process, complicated and varied matrix are difficult to eliminate by commonly methods. Molecularly imprinted is a simple, economical and efficient pretreatment method, achieving high-sensitivity and selectivity detection. The main study is giving as follows:Molecularly non-covalent imprinted silica nanospheres of bisphenol A were synthesized with a sol-gel process on the supporter of silica nanospheres. The BPA-imprinted silica nanospheres were characterized by scanning electron microscope, dynamic adsorption, static adsorption tests and molecular selectivity tests. Scatchard analysis revealed that two classes of binding sites were formed in the imprinted polymers, the equilibrium association constant and the apparent maximum number of binding sites were estimated to be0.69μmol·ml-1and250.73μmol·ml-1, respectively. Bisphenol A and three analogues, tetrabromobisphenol A (TBBPA), bisphenol C (BPC) and nonylphenol (NP) were employed for selectivity tests. The results indicated that the imprinted polymers exhibited excellent selectivity and specificity toward bisphenol A.A nano-sized, efficient and surface covalent BPA-imprinted silica sorbent was prepared with a sol-gel process. The BPA-imprinted silica nanospheres showed high adsorption capacity and selectivity, and offered a fast kinetics for the rebinding of BPA. Scatchard analysis revealed that two classes of binding sites were formed in the imprinted polymers, the equilibrium association constant and the apparent maximum number of binding sites were estimated to be5.35μmol·ml-1and1087.21μmol·ml-1, respectively.The experimental results have demonstrated that the BPA-imprinted silica nanospheres is suitable to enrich and detect trace bisphenol A in environmental, biological and food samples.The covalent and non-covalent BPA-imprinted silica nanospheres, as the solid-phase extraction (SPE) sorbents, the SPE conditions were optimized, and dichloromethane was selected as the loading solvent. The selective extraction of BPA from BPA and its three structural analogues BPC, TBBPA and NP showed that the BPA-imprinted silica nanoparticles SPE column had much higher selectivity for BPA with recoveries of90.7%and88.7%, respectively. The canned food samples spiked at two concentration levels of2.5and5μmol·ml-1BPA were prepared by non-covalent BPA-imprinted silica nanospheres SPE column and determined by HPLC with recoveries of72%～84%and relative standard deviations(n=3) of2.9%-4.4%. The canned food samples spiked at two concentration levels of5and10μmol·ml-1BPA were prepared by covalent BPA-imprinted silica nanospheres SPE column and determined by HPLC with recoveries of77%～90%and relative standard deviations(n=3) of3.6%～5.7%.