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Preparation of silica gel surface of nonylphenol molecularly imprinted polymer and its application in solid phase extraction

Author: LiWenYan
Tutor: WangBinSong
School: Heilongjiang University
Course: Environmental Science
Keywords: surface molecularly imprinting nonylphenol silica gel solid-phaseextraction
CLC: O658.2
Type: Master's thesis
Year: 2013
Downloads: 37
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Abstract


Nonylphenol (NP) is a typical endocrine disrupting chemical that can disturb the proper functioning of the endocrine system in organisms. In recent years, the determination and analysis of NP-containing samples is particularly important along with the widely using of NP in industrial production and daily life. However, samples containing NP are of complicated matrices, so determination of NP often requires effective separation and enrichment in sample preparation prior to instrumental analysis. Solid-phase extraction (SPE) is the most popular sample pretreatment method today. Unfortunately, traditional SPE sorbents show unsatisfactory selectivity for NP in complex matrices and this makes the follow-up analysis of NP very difficult. So it is necessary to synthesize an effective sorbent with high selectivity for the separation and enrichment of NP from NP-containing samples. Molecular imprinting technique (MIT) is a preparation process of specific selective polymer for a particular target molecule. With the advantages of simple preparation, good binding property, high selectivity, long working life, molecularly imprinted polymers (MIPs) have been extensive researched in many fields such as:solid-phase extraction, sensor, reaction catalysis. So it is valuable to research selective recognition of NP for separation and enrichment through MIT.In this paper, we successfully synthesized MIPs with advantageous morphology by the surface molecular imprinting technique coupled with sol-gel process on the surface of silica gel particles which overcome the disadvantages prepared by conventional method such as irregular shape and deeply embedded recognition sites inside matrix particles which may lead to poor binding capacity and lower binding kinetic of MIPs towards the template molecules, as well as difficult elution because of the existence of diffusion barrier. The effects on NP removal rate of the different silica gel carrier, functional monomer, solvent, crosslinker are investigated and the preparation of MIPs was optimized. Characterization of the physical and chemical properties of Silica-MIPs was done by using scanning electron microscopic (SEM), Fourier transform infrared spectrometer (FT-IR), EDS analysis, thermogravimetric analyzer (TGA) and nitrogen adsorption-desorption which revealing that molecularly imprinted polymers grafted onto the silica surface successfully. The content of imprinted polymers were estimated as high as5.08wt%. Silica-MIPs showed an average pore diameter of3.87nm and the calculated BET specific surface area of Silica-MIPs was336.84m2/g. The the surface of Silica-MIPs formed a porous and cross-linked network structure.The adsorption kinetic, adsorption isotherm, adsorption selectivity and regeneration reuse were measured to evaluate the adsorption characteristics to NP. The results of the kinetic studies showed that the adsorption reached equilibrium in about10min. The adsorption quantity of Silica-MIPs were8.812mg/g. By further analyzing according to calculation with Scatchard analysis, the equilibrium dissociation constant and the maximum apparent adsorption quantity of binding sites of Silica-MIPs were0.335mg/L and17.273mg/g, respectively. The removal efficiency for NP, phenol and OP by Silica-MIPs were81.19%,29.51%and25.23%, respectively, which indicated Silica-MIPs had the highest adsorption selectivity towards NP. In the test of regeneration reuse, five regeneration cycles were measured without obvious decrease in the adsorption capacity for NP. The results mentioned above indicated that Silica-MIPs had not only high adsorption capacity and adsorption selectivity for NP, but also good regeneration and stability.MIPs-SPE was evaluated to investigate the retention capability to NP, OP and phenol. The recovery rate of MIPs-SPE to NP is96.75%, however, the recovery rate to OP and phenol are less than50%. The results of SPE with different sorbents shows that the retention capability of MIPs-SPE to NP is significantly superior to NMIPs-SPE and C18-SPE. The selectively enrichment effect of MIPs-SPE to NP shows that the baseline interference indicate a weaker effect and ensure sufficient quantitation. But the NP of sample with NIP-SPE is not enough to quantitate and the other impurities with C18-SPE seriously interfere with the determine of NP. The recovery rate of MIPs-SPE to NP is87.2～94.3%with RSD=2.7～5.3%(n=5) which shows good results.

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CLC: > Mathematical sciences and chemical > Chemistry > Analytical Chemistry > Separation of elements and compounds > Extraction method
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