Preparation Of Molecularly Imprinted Layer-coated Silica Nanoparticles For Bpa And Its Application In Solid-phase Extraction

Bisphenol A (2,2-bis(4-hydroxyphenyl)propane, BPA), a kind of environmental endocrine disruptors (EEDs), has been shown to disturb endocrine secretion of human and other animals, and induce malignant tumour of reproductive organs. Because of its wide dispersive, monitoring of BPA has been given rise to international concern. Nowadays, BPA are often monitored by GC, HPLC and chromatography-mass spectra. In general, samples containing BPA are of complicated matrices, and BPA exists in very low concentration. So, effective sample preparation prior to instrumental analysis is extremely important. Solid-phase extraction (SPE) is by far the most used technique for the extraction of BPA from BPA-containing samples. Unfortunately, traditional SPE sorbents, such as C18, PS-DVB (Poly(styrene-co-divinylbenzene)) and graphitized carbon black, show a lack of selectivity. The interferents will be extracted with BPA together, which makes the follow-up analysis of BPA very difficult.Molecularly imprinted polymers (MIP) belong to functional high molecule polymer with specific recognition sites for template and partial binding for structure analogues. The combination of MIP and solid-phase extraction (namely molecularly imprinted solid-phase extraction, MIP-SPE) has become a fast, simple and effective pre-preparation method for complicated matrices. Application of MIP-SPE has been one of the most promising development aspects of MIP. In the dissertation, molecularly imprinted layer-coated silica nanoparticles for BPA (BPA-MIP) were prepared with a sol–gel process on the supporter of silica nanoparticles, and used as sorbents of SPE. An off-line MIP-SPE coupled with HPLC method was established for the determination of BPA from shampoo, bath lotion and cosmetic cream samples.1. Preparation and characterization of BPA-imprinted silica nanoparticles Molecularly imprinted layer-coated silica nanoparticles for bisphenol A (BPA) were synthesized by molecular imprinting technique with a sol–gel process on the supporter of silica nanoparticles. The BPA-imprinted silica nanoparticles were characterized by fourier transform infrared spectrometer, transmission electron microscope, static adsorption and dynamic adsorption tests. BPA adsorption reached the equilibrium within 40 min. The static adsorption capacity of BPA-imprinted sorbent was about 2.5 times that of non-molecularly imprinted polymers (NMIP). The equilibrium association constant, Ka, and the apparent maximum number of binding sites, Qmax, were estimated to be 1.25×105 mL·μmol?1 and 16.4μmol·g?1, by Scatchard analysis respectively. The results of the study indicated that the prepared BPA-imprinted silica nanoparticles exhibited high adsorption capacity and selectivity, and offered a fast kinetics for the rebinding of BPA.2. Evaluation of MIP-SPE and its applicationA MIP-SPE column was prepared using the optimized BPA-MIP as sorbents. The breakthrough volume and mass capacity of MIP-SPE were 250 mL (12.5 nmol BPA) and 25μmol·g?1, respectively. Compared with NMIP-SPE column and C18-SPE column, MIP-SPE column showed selective extraction and satisfactory recovery for BPA from BPA and its three structural analogues. The BPA recoveries by MIP-SPE column corresponding to the mixed solutions were 96.7±4.7%(1:1), 95.9±2.2%(1:2), and 99.9±1.8%(1:3), respectively.An off-line MIP-SPE and HPLC-FLD method was established for the determination of BPA from shampoo, bath lotion and cosmetic cream samples. The comparison between MIP-SPE column and C18-SPE column clearly demonstrated the advantage of BPA-imprinted silica sorbent as selective sorbent for the determination of BPA in spiked shampoo, bath lotion and cosmetic cream samples. The correlation coefficient of the calibration curve was very satisfactory (r = 0.9997) in the concentration range (0.0003—0.05μmol·L?1). The LOD (limit of detection) and the LOQ (limit of quantitation) were 0.0001μmol·L?1 and 0.0003μmol·L?1, respectively. As could be seen, the average recoveries at the middle concentration of the MIP-SPE method for shampoo, bath lotion and cosmetic cream were 97.3%, 92.1% and 87.3%, respectively, with RSD <9%(n=5). The results demonstrated that the MIP-SPE had good recovery and reproducibility, and could satisfy the determination of BPA in shampoo, bath lotion and cosmetic cream samples.