Bisfenol A Tanıma Bölgelerine Sahip Moleküler Baskılanmış Polimerik Kartuşların ve Sensör Sisteminin Geliştirilmesi
Özet
Bisphenol A (BPA) which is an endocrine disrupting chemical, has adverse effects on human health such as diabetes, prostate and breast cancer. Due to its widespread use, it threatens human health by contaminating water resources, soil and food. For this reason, there is a need for systems for the selective removal and determination of BPA from water, which is the easiest contamination source for people to access. In the course of the thesis, molecularly imprinted systems have been developed for selective identification and removal of BPA from water. In the first part of the study, molecularly imprinted polymeric cartridges were prepared for pre-concentration and removal of BPA from water. To prepare polymeric cartridges, N-methacryloyl-L-phenylalanine (MAPA), ethyleneglycol dimethacrylate (EDMA), ethanol (EtOH) and azobisisobutyronitrile (AIBN) were used as a functional monomer, crosslinker, porogen and initiator, respectively. The ratio of component of BPA-MAPA pre-complex used in preparation of the imprinted polymeric cartridges (BMC) was determined to be 1:3 by UV-Visible spectrophotometer. In order to determine the imprinting effect, non-imprinted polymeric cartridges (BNC) in the absence of template molecule and empty polymeric cartridges (EC) in the absence of template molecule and functional monomer were also prepared, following the same procedure as described. The structural characterization of the polymeric cartridges was determined by FTIR and elemental analysis methods, while the characterization of surface properties was determined by swelling tests, SEM and BET surface area measurements. The effect of ambient conditions (i.e. pH, flow rate, BPA concentration, temperature, salt type and concentration) on BPA adsorption capacity was also investigated. The optimum ambient conditions giving the highest capacity were determined as 200 mg/L BPA solution containing 0.75 M (NH4)2SO4 for 0.75 mL/min flow rate and at 50° C ambient temperature. The highest adsorption capacity for BMC was determined as 103.2 mg BPA/g of polymer. Hydroquinone, phenol, 8-hydroxyquinoline and β-estradiol (competitors), which are structurally similar to the target molecule, have been used in determining the selectivity of the imprinted polymeric cartridge. Reusability experiments were performed by 10 consecutive adsorption-desorption cycles. Langmuir, Freundlich, Temkin and Dubinin-Radushkevich adsorption isotherm models were applied to adsorption data. It has been determined that the most suitable isotherm model for the adsorption of BPA is Langmuir. Adsorption thermodynamic parameters (ΔHo, ΔSo ve ΔGo) were calculated by using thermodynamic equilibrium constant values at different temperatures (thermodynamic equilibrium constant, Ko). BPA adsorption kinetic was investigated by applying pseudo first order and pseudo second order models to the experimental data. The result is consistent with the pseudo-second order kinetic model which predicts that the BPA adsorption to the polymeric cartridge surface is chemically controlled without any diffusion restriction. Solid phase extraction performance of BMCs was also performed with BPA solutions prepared by using tap water and synthetic wastewater. Extraction recovery (ER) values from tap water ranged from 92% to 96%, while this value varied from 89% to 94% for synthetic wastewater samples. In addition, the enrichment factor (EF) values calculated by considering solution volumes used for adsorption and desorption were determined as 18.4-19.1 and 17.9-18.8 for tap water and synthetic wastewater, respectively.
In the second part of the study, molecular imprinting technology based optical sensors were developed for the detection of BPA from water. Molecularly imprinted nanoparticles (BIN) were prepared by two-phase mini-emulsion polymerization method by using vinylimidazole (VIM) and ethyleneglycolmethacrylate (EDMA) as functional monomer and cross-linker, respectively. Grafene quantum dots (GODs) prepared by hydrothermal pyrolysis method have been immobilized on the surface of nanoparticles to acquire fluorescence properties to BIN. Nitrocellulose paper was used for the easy application of the prepared BPA-imprinted optical nanosensor (GBIN). FTIR, zeta-size analysis, TEM, SEM, spectrofluorimetric measurements were used to characterize the as-prepared sensor system. The GBIN nanosensor achieved 15.4 µg/L limit of detection (LOD) and 47.7 µg/L limit of quantification (LOQ) in aqueous phase applications. In the nitrocellulose application of GBIN nanosensor, LODs for tap water and sea water samples were determined as 0.5 µg/L and 1.0 µg/L, while LOQs were 1.7 µg/L and 3.4 µg/L, respectively. The selectivity and specificity of the sensor system have been investigated with sensor response in both sea water and ultrapure water samples by using BPA as well as structural analogues such as aminophenol, phenol, hydroquinone and naphthol as competitor agents. These results show that the systems based on molecular imprinting for the removal and determination of BPA from different matrices were satisfactory.
