Master Degree / Yüksek Lisans Tezleri
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Master Thesis Preparation of Molecularly Imprinted Polymers for the Solid Phase Extraction of Pyridoxal 5'-phosphate Prior To Hplc Determination(Izmir Institute of Technology, 2022) Özyurt, Ömer; Eroğlu, Ahmet EminThree different sorbent materials were prepared for solid phase extraction of pyridoxal phosphate (PLP), namely, carbon sphere based molecularly imprinted chitosan polymer (MICP), magnetite based molecularly imprinted chitosan polymer (MMICP) and silica (sol-gel) based molecularly imprinted polymer (IMIP). The sorbents were characterized by FT-IR, SEM, EDX, XRD, and TGA. The characterization data have shown that, the sorbents were relatively homogeneous, had very fast sorption kinetics and quantitative sorption over a wide range of analyte concentrations (1.0-100.0 mg/L). All the sorbents were found to be selective to PLP in presence of similar compounds; namely, pyridoxamine, nicotinic acid (vitamin B3), pyridoxal and 4-pyridoxic acid. Sorption parameters for each sorbent were optimized. The optimum sorbent amount for 10.0 mL sample volume was found to be 5.0 mg for MICP and 10.0 mg for both MMICP and IMIP. A shaking duration of 30 min was employed in sorption experiments. Among the potential eluents, acetic acid solution (2%, v/v) has shown the best desorption performance for all three sorbents. Method validation was investigated via spike recovery tests on water (ultra-pure, bottled and tap) and artificial serum samples. The recoveries obtained with water samples were greater than 96%, 92%, and 91% for MICP, MMICP, and IMIP, respectively. These results show the potential application of the methodologies for samples with relatively simple matrix. High recoveries (greater than 80%) were also obtained with artificial serum samples, whereas the use of matrix-matched calibration or internal standardization is suggested together with protein precipitation for biological samples with high protein content.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 Fabrication of Colorimetric Ph Indicator Films by Electrospinning(Izmir Institute of Technology, 2022) Erez, Elif; Bayramoğlu, Beste; Eroğlu, Ahmet EminThe trend in the food packaging industry evolves towards innovative packaging materials as biosensors, which record the status of the product and can warn the consumer. The logic behind the colorimetric pH biosensor is that they provide the essential information about food visually by detecting change in pH. Anthocyanins are natural color pigments susceptible to pH change. Purple basil is rich in anthocyanins. In this study, ultrasound-assisted extraction was used for the extraction of dry purple basil. The processing conditions were optimized by response surface methodology (RSM) in terms of the total monomeric anthocyanin content and the increase in green intensity with pH. Electrospinning is a nanofiber fabrication operation used to encapsulate sensitive bioactive compounds for the production of intelligent sensing system. Polycaprolactone (PCL) films incorporating different purple basil extract (PBE) concentrations were fabricated by electrospinning procedure for the usage of colorimetric pH-indicator films as intelligent packaging. The most beadles and uniform nanofibrous mats were obtained when the spinning conditions were V=20 kV and Q=0.4 mL h-1for 10% (w v-1) PCLsolutions containing 0.4% and 0.6% (w v-1) PBE. The average fiber diameters in these films were 178.59±52.92 nm and 235.39±92.46 nm, respectively. The films gave promising results with regards to their use as colorimetric pH-indicator films. The time required to observe a visible color change (ΔE) in these films was only 4-5 s. The ΔE values between all successive pH’s were higher than 2, which is detectable by an inexperienced observer. Keywords: Anthocyanin, Purple Basil, Ultrasound-Assisted Extraction, Response Surface Methodology (RSM), Electrospinning, Colorimetric pH-indicator Films.Master Thesis Development of Novel Columns for Determination of Various Ss-Blockers by Capillary Electrochromatography(Izmir Institute of Technology, 2018) Gürel, Elif; Eroğlu, Ahmet Eminß-blockers are one group of the most widely used drugs to treat heart failure, high blood pressure and abnormal heart rhythms. The purpose of this study was to develop capillary columns of stationary phases from molecular imprinting and sol-gel methodology for the determination of ß-blockers prior to capillary electrochromatography (CEC) analysis. In the first part of the study, molecularly imprinted organic based polymers (MIPs), silica-based molecularly imprinted polymers (SMIPs) and silica-based sorbents were developed, characterized and utilized for sorption of metoprolol, an example of ß-blockers. The three different types of sorbents were studied as stationary phases of capillary column. Critical parameters on sorption of metoprolol were investigated. In the second part, the subsequent studies were concentrated on the preparation new capillary column for separation and determination of metoprolol for CEC analysis. The performance of three different types of sorbents was compared. Molecularly imprinted organic polymers show higher sorption and selectivity towards metoprolol as compared with the other sorbent types. The preparation of stationary phases of capillary columns with molecular imprinted organic polymers was proposed for determination of metoprolol prior to CEC analysis. After stationary phase optimization studies, an open tubular column was prepared and its performance was examined.Master Thesis Development of Novel Columns for Determination of Various Diuretics by Capillary Electrochromatography(Izmir Institute of Technology, 2018) Yaşar, Cemre; Eroğlu, Ahmet EminDiuretics are active pharmaceutical compounds that are used for the treatment of edema, cirrhosis, hypertension and renal failure. World Anti-Doping Agency has announced diuretics as banned compounds. Because they are used as a masking and doping agent. In this study, target compounds are therapeutically important groups of this active pharmaceuticals; namely thiazides (bendroflumethiazide, chlorothiazide, hydrochlorothiazide). Sol-gel chemistry and molecularly imprinted polymers (MIPs) methodology were offered for preparing the column for capillary electrochromatography (CEC) for determination of thiazides. Modified silica sol-gel (amine and phenyl modified) and MIPs were synthesized through different routes (inorganic and organic form) as filling materials for capillary columns. Materials which were filled into the column were selected by the help of sorption studies prior to CE-DAD analysis. For this purpose, critical experimental parameters of CE-DAD were optimized and determined as follows; background electrolyte type of borate buffer (10mM) and pH of 9.4, voltage of 25 kV, cassette temperature of 30℃. Limit of detection (LOD) were calculated as between 0.20 mg L-1 and 0.30 mg L-1. Limit of quantification (LOQ) was found as between 0.44 mg L-1 and 0.99 mg L-1. Finally, sorbents having best sorption capacity towards the analytes were prepared as a stationary phase of capillary column and analysis was done with CEC-DAD.Master Thesis Solid Phase Extraction of Ibuprofen in Waters With Molecularly Imprinted Polymers Prior To Hplc-Dad Determination(İzmir Institute of Technology, 2016) Ölçer, Yekta Arya; Eroğlu, Ahmet EminEndocrine disrupting compounds (EDCs) attract great attention worldwide due to their undesired effects on human health. Ibuprofen, an example of endocrine disrupters, is a nonsteroidal anti-inflammatory drug (NSAID). In this study, highly selective molecularly imprinted polymers (MIPs) with different morphologies (as monolith and microspherical beads) were synthesized by bulk and precipitation polymerization strategies. MIPs were prepared by using acetonitrile as porogen, methacrylic acid (MAA) as monomer, trimethylolpropane trimethacrylate (TRIM) as crosslinker and the analyte, ibuprofen, as the template. MIPs revealed higher affinity to the template molecule as compared with non-imprinted polymers (NIPs). The MIP prepared by precipitation polymerization was decided to be used as the primary solid phase extraction (SPE) sorbent due to its higher binding capacity towards ibuprofen compared to the MIP prepared by bulk polymerization. Selectivity of MIP to ibuprofen was examined in the presence of structurally related compounds. In this study, a molecular imprinting solid phase extraction (MISPE) methodology was proposed for determination of ibuprofen prior to HPLC-DAD analysis. For this purpose, critical experimental parameters of MISPE method were optimized and determined as follows; solution pH of 8.0, sorbent amount of 25.0 mg for 10.0 mL of 1.0 mgL-1 working solution, sorption time of 30 min and MeOH:H2O (acetic acid, pH 3.0) ratio of 80:20 as desorption solution. The accuracy of the proposed methodology was verified with spike recovery tests for tap and drinking waters and overall recovery was found as 97.4 (± 0.3) for n=3.Master Thesis Preconcentration of Rare Earth Elements (rees) Using Silica Gel Modified With Several Functional Groups(Izmir Institute of Technology, 2007) Ünal, Semira; Eroğlu, Ahmet Emin; Eroğlu, Ahmet EminDetermination of rare earth elements (REEs) in environmental samples can be performed by inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS), in addition to other spectrometric and chromatographic methods. Although these plasma-based techniques offer a good quality data for the determination of REEs, an efficient separation/preconcentration technique prior to instrumental measurements may still be required due to low concentrations and the presence of heavy matrix, in order to achieve accurate and reliable results. In this study, silica gel modified with various organic compound containing S and N functional groups was proposed as adsorbent material for preconcentration of REEs in environmental waters before ICP-MS determination. These organic compounds are (3-aminopropyl)trimethoxysilane (APTMS), (3-mercaptopropyl) trimethoxysilane (MPTMS), 2.aminophenol, 2-aminothiophenol, 2-aminobenzothiazole and L-glutamic acid dimethyl ester. It was shown that REEs can be sorbed by only APTMS and MPTMS modified silica gel quantitatively in a broad pH range (pH>3). At high REEs concentration APTMS modified silica gel (silicaamino) worked better than silica gel. Up to 10.0 mg/L, silica-amino have sorbed higher than 80% of the REEs while silica gel could sorb only 30% of them. Among the sorbents investigated silica-amino was chosen for subsequent experiments. Desorption from APTMS modified silica and silica gel was realised with 1.0 M HNO3. Spike recovery tests were performed in various water types including ultra pure water, sea water, tap water and geothermal water and were found to change between 81-110%.Master Thesis Biosorption of Aqueus Pb2+, Cd2+, and Ni2+ Ions by Dunaliella Salina, Oocystis Sp., Porphyridium Cruentum, and Scenedesmus Protuberans Prior To Atomic Spectrometric Determination(Izmir Institute of Technology, 2008) Karaca, Meral; Eroğlu, Ahmet EminIn this study, the possibility of using four different algae for the sorption of heavy metals, namely, Pb, Cd, and Ni, from waters was investigated. Dunaliella salina, Oocystis sp., Porphyridium cruentum, and Scenedesmus protuberans were shown to be good candidates for the sorption/removal of the metals from waters prior to atomic spectrometric determination. Characterization of the algae was carried out by scanning electron microscopy, FTIR, elemental analysis, and thermogravimetric analysis.All biomasses behaved similarly in the optimization of sorption parameters.Solution pH of 6.0, sorbent amount of 10.0 mg for 10.0 mL sample volume, shaking time of 60 min, and reaction temperature of 25C were used in the sorption experiments. It was demonstrated that the primary sorption mechanism is the electrostatic attraction between the negatively charged functional groups on the surface of the biomass and the positively (+2) charged metal ions in the solution. Among the biomasses investigated, Dunaliella salina has shown the highest sorption capacity for all the metal ions. It was followed by Oocystis sp., Scenedesmus protuberans and Porphyridium cruentum. Additionally, the biomasses examined have demonstrated the highest affinity towards Pb2+ which was followed by Cd2+ and Ni2+.The competitive biosorption experiments have shown that the uptake of Pb2+ ions was not influenced by the presence of other ions for all the algae studied.However, the general trend for the other biomasses was a decrease in their sorption efficiency towards Cd2+ and Ni2+ ions with the increase in the concentration of the competitive ions.It can be proposed that the algal biomasses investigated in this study can be utilized successfully in the sorption and selective removal of the studied heavy metal ions from waters.Master Thesis Speciation of Chromium in Waters Via Sol-Gel Preconcentration Prior To Atomic Spectrometric Determination(Izmir Institute of Technology, 2007) Kumral, Elif; Eroğlu, Ahmet EminChromium occurs in natural samples in two relatively stable valence states, i.e. in the form of Cr(III) and Cr(VI) species. Their concentration in natural waters is usually very low, in the order of a few .g/L. This low concentration necessitates either the use of very sensitive analytical techniques or the application of suitable preconcentration methods prior to instrumental determination. In the present study, a resin having immobilized mercapto or amino functional groups was prepared by reacting silica gel with 3-mercaptopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, L-glutamic acid dimethyl ester, aminophenol, aminothiophenol and aminobenzothiazol for the preconcentration of Cr(III) and Cr(VI) species in waters prior to their determination by flame atomic absorption spectrometry (FAAS). Characterization of the novel sorbents were performed using scanning electron microscopy (SEM/EDS), thermo gravimetric analysis (TGA) and elemental analysis. Among the sorbents synthesized, amino sol-gel and silica amino have been shown to be efficient in terms of sorption capacity. The applicability of the new sorbents for the preconcentration of Cr(III) and Cr(VI) species in waters was examined by batch method. After pH 4, silica amino could quantitatively sorb both Cr(III) and Cr(VI) whereas amino sol-gel sorbed only Cr(III). Effect of the amount of silica amino and amino sol-gel was examined at the optimum pH. The optimum amount of silica amino for quantitative sorption was found to be 0.1 g for 20.0 mL of 1.0 mg/L Cr(III) and Cr(VI) solutions whereas that of amino sol-gel was 0.05 g for 20.0 mL of 1.0 mg/L for both species. The effect of Cr(III) and Cr(VI) concentrations on amino sol-gel and silica amino were investigated at the initial concentrations of 1.0, 10.0, 25.0 and 50.0 mg/L. Elution was realized with 2.0 M HCl, and the percent recovery values changed between 60 and 80%.Master Thesis Speciation and Preconcentration of Inorganic Antimony and Manganese in Waters Using Microcolumn-Flow Injection System and Determination by Atomic Absorption Spectrometry(Izmir Institute of Technology, 2003) Erdem, Aslı; Eroğlu, Ahmet EminA selective separation/preconcentration method utilizing microcolumn of a chelating resin with -SH functional groups (Duolite GT-73) was proposed for the determination of Sb(III) in waters by segmented flow injection HGAAS. The selectivity of the resin towards Sb(III) and Sb(V) was not dependent on the pH of the solution; Sb(III) was retained by the resin quantitatively in a broad pH and acidity range whereas Sb(V) was not retained at all and could be determined after a pre-reduction step with L-cysteine.Spike recoveries were tested at various concentration levels in different water types and were found to vary between 80-110 %. Accuracy of the proposed methodology was checked by analyzing a standard reference material and a good correlation was found between the determined and the certified values. The method was applied to several bottled drinking water samples for antimony determination. The samples were found to contain no antimony above the permissible level (5 ug/L). The applicability of the microcolumn separation/preconcentration method for flow injection systems was also demonstrated.A similar separation system was proposed for Mn determination in waters. A macroporous resin with no functional groups (Amberlite XAD-7HP) was employed for the speciation of Mn(II) and Mn(VII) and was found to retain Mn(VII) at pH values from 4.0 to 12.0. Mn(II) was retained at a pH of 12.0, possibly due to MnO2 precipitation rather than adsorption by the resin.