Phd Degree / Doktora

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Access Right: Open AccessSubject: search.filters.subject.Solid phase microextraction

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  • Doctoral Thesis
    Development of Novel Solid Phase Extraction (spe) Sorbents and Solid Phase Microextraction (spme) Fiber Coatings for Determination of Endocrine Disrupting Compounds (edcs)
    (Izmir Institute of Technology, 2017) Demirkurt, Merve; Eroğlu, Ahmet Emin
    This thesis is composed of four chapters. In the first part of the study, molecularly imprinted polymer (MIP) was prepared as SPE sorbent for selective determination of BPA prior to HPLC DAD analysis. The adsorption capacity and selectivity of imprinted polymers were investigated. To improve the MISPE method, the parameters including pH of sample solution, adsorption time, amount of sorbent, desorption solvent were examined. The extraction efficiency of BPA imprinted polymer was investigated by using the spiked samples of ultrapure, drinking and tap water. The second part of the thesis was about determination of estrogen hormones. For this purpose, amino modified silica and molecular imprinted silica were prepared and their SPE performances were compared. The proposed methodology was validated through the analysis of real water samples. The preparation of MIP nanoparticles encapsulated in electrospun polystyrene fibers as the SPME fiber coating was the subject of the third part of the thesis. Developed fibers were used for selective extraction and analysis of parabens in water samples. The optimization parameters affecting the extraction and desorption of parabens were investigated. The validity of the proposed method was verified via spike recovery tests. Finally, fibers having amino functionality prepared by the sol-gel based electrospinning process were used for determination of BPA. The effect of solution pH, extraction time, agitation speed and ionic strength on the extraction performance were investigated. Validity was checked via the application of the proposed methodology on real samples.
  • Doctoral Thesis
    Development of Solid Phase Microextraction (spme) Fibers for Various Analytical Applications: (i) Selenium Speciation in Waters. (ii) Separation and Determination of Triclosan and Triclocarban in Waters
    (İzmir Institute of Technology, 2016) Ziyanak, Esen; Eroğlu, Ahmet Emin
    In the first part of this study, four selenium species namely selenite, selenate, selenomethionine and selenocystine in water samples were tried to be separated using single solid phase microextraction (SPME) fiber on the same chromatographic run. Bare silica fibers were immersed into agarose matrix containing nano zerovalent iron (nZVI), ceria (CeO2) or zirconia (ZrO2). After characterization of fibers sorption/desorption parameters were optimized and standard reference materials were used to validate the proposed method. Direct mode of SPME method was used to extract the analytes prior to their separation with HPLC and detection with ICPMS. The optimum conditions for the extraction of selenium species with nZVI-agarose fibers are obtained as extraction pH: 4.0, agitation speed: 700 rpm, extraction time: 60 min, desorption matrix: 10.0 mM citrate solution, desorption time: 30 min, solution temperature: 25 °C, ionic strength: no NaCl addition. In the second part of this study, same fibers were used to separate triclosan (TCS) and triclocarban (TCC) using HPLC-DAD. Among all fibers prepared, nZVI-agarose modified fibers demonstrated the best extraction performance. The optimum conditions for the extraction of TCS and TCC with nZVI-agarose fibers are obtained as extraction pH: 5.0 and 7.0, agitation speed: 400 rpm, extraction time 60 min, desorption matrix: % 90 methanol - %10 water (adjusted to pH 3.0 with acetic acid), desorption time: 30 min, ionic strength: no NaCl addition.
  • Doctoral Thesis
    Preparation of Novel Fiber Coatings for Solid Phase Microextraction of Flavonoids
    (Izmir Institute of Technology, 2014) Esen, Meral; Eroğlu, Ahmet Emin
    Many plant species contain flavonoids which are widely utilized in food, pharmaceutical and cosmetics industries as additives. Literature studies show that most of the earliest drugs were of plant origin. Application of flavonoids in many fields necessitates the development of new extraction and determination methods in various samples. In this study, three different types of solid phase microextraction (SPME) coatings were produced. The first one is baicalin- and imidazole-functionalized silica fibers via sol-gel method. Both manual and dip-coating were employed. The fibers were examined by SEM and the results show that dip-coating produced more homogeneous coatings. The second one is polystyrene templated monolithic silica. Then, it was functionalized with baicalin and imidazole groups. The last solid phase microextraction coating is molecularly imprinted silica. In this case, a sol-gel process was used to synthesize molecularly imprinted silica with tetraethoxysilane (TEOS) as the crosslinking agent, aminopropytriethoxysilane (APTES) as a functional monomer, quercetin as the template molecule, and AlCl3 as a Lewis acid. Characterization of baicalin-functionalized monolithic silica and molecularly imprinted silica was achieved by SEM, FTIR, TGA and elemental analysis. SPME process was followed by HPLCDAD at 335 nm after separation of flavonoids on a Zorbax Eclipse XDB-C18 (5μm, 4.6x150mm) column at 25.0°C with gradient elution using methanol and water (containing 0.10% acetic acid). Functionalized silica fibers were utilized in solid phase microextraction of apigenin, apigetrin, eriodictyol, isoquercitrin, luteolin, and quercetin. The results demonstrated that higher extraction efficiency can be obtained with baicalinfunctionalized monolithic silica and molecularly imprinted silica coated fibers.