Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Development of Molecularly Imprinted Solid Phase Extraction Method for the Detemination of Vitamin D Derivatives(Izmir Institute of Technology, 2022) Tosun Kurtalan, Hazal; Eroğlu, Ahmet Emin; Eroğlu, Ahmet EminVitamin D, also known as the sunshine vitamin, is both a micronutrient and a prohormone. There are two structurally different forms of vitamin D: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Both forms can be taken into the body through food or dietary supplements. In addition, ergocalciferol and cholecalciferol can be synthesized non-enzymatically by UVB radiation of sunlight from provitamin forms, which are ergosterol and 7-dehydrocholesterol. In this study, a methodology based on molecularly imprinted solid phase extraction (MISPE) is intended prior to the determination of D2 and D3 by HPLCDAD. In accordance with this purpose, precipitation and sol-gel polymerization methods were used to synthesize molecularly imprinted polymers (MIPs) and nonimprinted polymers (NIPs). Also, different templates, monomers, crosslinkers, and their ratios were tried in the synthesis of MIPs/NIPs by precipitation polymerization. Among all syntheses, MIP, which was synthesized using vitamin D2 as template (T), 4- vinylpyridine (4-VP) as monomer (M), ethylene glycol dimethacrylate (EGDMA) as crosslinker (C) at a molar ratio of 1:6:30 (T:M:C), enabled the co-determination of vitamin D2 and D3. It selectively worked on the vitamin D prohormone group compared to both NIP and commercial solid phase extraction (SPE) sorbents in the presence of other structurally related compounds. The critical experimental parameters of the MISPE method were optimized for the analyte concentration of 1.0 mgL-1 and determined as follows: 8 hours as the sorption time, 5.0 mg as the sorbent amount, 5.0 mL as the sample solution volume, methanol as the eluent, and 24 hours as the desorption time. A matrix-matched calibration curve with optimized parameters was proposed. The applicability of the developed MISPE method was confirmed by analyzing the sample of vitamin D3 supplementation and overall recovery was found as 95.97% (±1.84) for n=2.Master Thesis Solid Phase Extraction of Ascorbic Acid With Zero-Valent Iron Nanoparticles(01. Izmir Institute of Technology, 2021) Yıldız, Cemre; Eroğlu, Ahmet EminVitamin C (ascorbic acid, AA) is an essential food for humans. It is a watersoluble vitamin found naturally in some foods. With its reducing and chelating capabilities, ascorbic acid is the most effective enhancer of non-heme iron absorption. Sensitive and selective determination of ascorbic acid is necessary in a variety of samples. In this study, molecularly imprinted polymers (MIPs) were synthesized by polymerization strategies and magnetic imprinting technology. Four different synthesis routes were employed, and the magnetic property of the MIPs was brought in with the use of nanosized zero-valent iron (nZVI). Nano zero-valent iron was synthesized using NaBH4 reduction of aqueous Fe+2 ions and used in the solid phase extraction of ascorbic acid prior to HPLC determination. The sorption percentage of the sorbent increased with icreasing pH and reached its maximum level between pH 6.0 and 8.0. Iron oxidation occurs very slowly if the pH is less than 6.0. As a result, when pH 8.0 and higher were tested, there was no effect. The precipitation of iron at pH 8.0 and above could have caused this. The pH level was fixed to 6.0, and the rest of the studies were carried out at this level. The optimal sorbent concentration, solvent concentration, and shaking time were determined to be 10.0 mg, 10.0 mL, and 1 hour, respectively. MeOH and MeOH: H2O, 85:15, were used to achieve desorption (pH of the eluent was adjusted to 3.0 using acetic acid). Finally, the characterization of synthesized nanosized zero-valent iron and magnetic MIP/NIP was carried out through the sorption studies and with the use of XRD, SEM and EDX.Master Thesis Preparati̇on of Fe and Fe-Ni Based Molecularly Imprinted Polymer for Solid Phase Extraction of Salicylic Acid(01. Izmir Institute of Technology, 2021) Bildik, Zeynep; Eroğlu, Ahmet EminAspirin is the most preferred pain reliever among the people. Salicylic acid (SA) is the drug active ingredient of aspirin and has an antipyretic, analgesic, and anti-inflammatory properties. It is also used in the treatment of acne, fungus, varicose veins, and calluses. The aim of this project is to prepare Fe and Fe-Ni based molecularly imprinted polymers (MIPs) for solid phase extraction of salicylic acid and then determine it with HPLC-DAD. MIPs were prepared by using methanol as porogen, 4- vinyl pyridine as monomer, ethylene glycol dimethacrylate cross linker and the analyte, salicylic acid, as the template. Fe and Fe-Ni is used to prevent the hydroxyl and carboxyl groups in the structure of salicylic acid from forming hydrogen bonds between themselves. In this study, a magnetic molecular imprinting solid phase extraction (MMISPE) methodology was proposed for determination of salicylic acid to HPLC-DAD analysis. For this goal, critical experimental parameters of MMISPE method were optimized and determined as follows; sorbent amount of 25.0 mg for 10.0 mL of 5.0 mgL-1 working solution, sorption time of 30 min and MeOH: Acetic acid (9:1) as desorption solvent. The proposed method was repeated with same sorbent and MIPs show quantitative sorption in three times. For characterization of MIPs and NIPs, EDX and XRD analysis was done. In XRD diffractogram, the peaks are relatively low intensities indicate that the material is mostly amorphous. Also, Fe and Ni peak cannot observe because of the trace amount of Fe and Ni in the polymer in the EDX graph.