Browsing by Author "Demirkurt, Merve"

Now showing 1 - 3 of 3

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, 2017-12) 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.
Development of novel sorbents for speciation of inorganic and organik selenium prior to determination by atomic spectrometric techniques
(Izmir Institute of Technology, 2011) Demirkurt, Merve; Eroğlu, Ahmet Emin
Selenium is an essential trace element forplants, animals and the human body. Hovewer, its possible toxicity at high concentrations necessitates the development of analytical methods for theseparation and determination of the several forms of the element in environmental andbiological systems.In the first part of the study, commercially available and newly synthesized ceria (CeO2) and zirconia (ZrO2) were used for the sorption and speciation of inorganic selenium. Sorption parameterswere investigated for both sorbents for selenite (Se(IV)) and selenate (Se(VI))and the optimized parameters were determined to be 25Â°C for sorption temperature, 50.0 mg for sorbent amount, 30 min for shaking time for 20.0 mLof 100.0 Î¼gL-1of both species. Therelease of Se(IV) and Se(VI) from the sorbents was realizedusing two eluents, 0.10 M NaOH and 0.10 NH4Cl, respectively. The accuracy of the proposedmethodology was verified with spike recovery tests for various water types spiked with 10.0 Î¼gL-1and 100.0 Î¼gL-1Se(IV) and Se(VI). Spike recovery values were determinedto range between 91% and 97% at 10.0 Î¼gL-1level, and between 97% and 113% at100.0 Î¼gL-1level, for ceria and zirconia, respectively. Moreover, the sorption efficiencies of the newly synthesized sorbentswere compared with those of the commercial sorbents.Ceria and zirconia were shown to be applied in the speciation of inorganic selenium. Sorption studies with nZVI-modified zirconia have demonstrated that the sorbent can be utilized for the speciation of inorganic and organoselenium; namely, Se(IV), Se(VI), Seleno-L-cystine and Seleno-DL-methionine. In the final part of the study, it was shown by column-type equilibration studies that alginate beads modified/immobilized with CeO2 or ZrO2through three different synthesis routes can be used for the sorption and speciation of inorganic selenium.
Recent developments of colorimetric mechanical sensors based on polymer composites
(Royal Soc Chemistry, 2020) Inci, Ezgi; Topcu, Gokhan; Guner, Tugrul; Demirkurt, Merve; Demir, Mustafa M.; Demir, Mustafa
Colorimetric mechanical (force, pressure, strain, and impact) sensors allow naked-eye visualization of existing structural deformations of a system occurring upon application of a mechanical action. The combination of mechanochromic materials with polymers offers a practical approach to designing and fabricating these sensors. Polymers as matrices can tolerate a wide range of forces and permits reusability of the sensors. On the other hand, mechanochromic materials provide unique colour properties depending on the type of mechanical action. They have also been frequently employed for the quantification of mechanical forces. As an example, non-centrosymmetric crystals are combined with polymers for sensing impact forces. Structures with photoluminescence and scattering and plasmonic resonances can be used to fabricate strain and pressure responsive composite materials, respectively. This study reviews recent advances in colorimetric mechanical sensor systems prepared using polymers and inorganic and organic mechanochromic materials working under a wide range of forces.