Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Development of a Fluidic Platform for Automated Analysis of Heavy Metals(Izmir Institute of Technology, 2019) Gülmez, Yekta; Tekin, Hüseyin Cumhur; Bulmuş, VolgaHeavy metals are part of Earth’s crust and the significant problem is accumulation of them in the ground waters. They have harmful results to body even they are at low concentration. Arsenic is one of the heavy metals which cause serious health problems such as; cancer, diabetes etc. Most of the developing countries are lack of detecting arsenic amount into drinking water. Therefore, especially in Bangladesh 1 out of 100 people die due to arsenic related cancer. According to World Health Organization, the maximum arsenic concentration in the drinking water must be 10 μg/L but the concentration amount reaches 50 μg/L or more at the developing countries. However, existing methods cannot detect arsenic at this range or the ones that can detect arsenic at the standard have so high prices that developing countries cannot afford. Therefore, the aim of this project is to develop a device for arsenic detection. In this thesis, a microfluidic chip was developed, and gold nanoparticles was used to detect arsenic in samples using absorbance spectroscopy. The detection principle was designed based absorption of arsenic and then gold on thiol-modified surfaces. The different concentration of arsenic samples was injected into microfluidic chip and 1.3 mg/L arsenic concentration could be detected. Then, syringe pump was added to the system and flow applied. As a result, the developed microfluidic chip is able to detect arsenic at 2.2 μg/L.Master Thesis Elucidation of Molecular Mechanisms Conferring Arsenic Tolerance To Yeast Cells(Izmir Institute of Technology, 2016) Işık, Esin; Karakaya, Hüseyin ÇağlarArsenic is a highly toxic metalloid available in the environment mainly as arsenite or arsenate. These compounds’ interference with many molecular mechanisms results in several diseases including cancer. Conversely, arsenic is used in therapeutic approaches, however, they are associated with drug resistance. Although some tolerance and toxicity mechanisms of arsenicals in yeast have been enlightened by previous studies, complete understanding, which is important for development of protection and therapy strategies, has not yet been achieved. Comprehensive genome-wide screening is a promising approach for the elucidation of novel genes involved in arsenic-associated mechanisms. The aim in this study was to screen a yeast genome library to characterize novel genes whose overexpression confers resistance to toxic concentrations of arsenate or arsenite in Saccharomyces cerevisiae. The plasmids from the colonies confirmed to be highly-resistant against arsenicals were sequenced to determine the genomic regions and seven genes were selected to clone into expression vectors. The overexpression of Pho86p and Vba3p provided yeast cells with the highest arsenate and arsenite resistance, respectively. Arsenate is a phosphate analogue and taken up by phosphate transporters. Pho86p is an ER-resident protein regulating ER-exit of the phosphate transporter. Therefore, it is reasonable that overexpression of Pho86p provides arsenate resistance. Vacuolar sequestration is a common route for the removal of toxic compounds from the cytosol and Vba3p is a vacuole-located transporter of basic amino acids with a likely role in arsenite resistance. Consequently, the screen in the current study revealed two genes with promising roles for tolerance mechanisms against arsenicals.Master Thesis Development of a Hybrid Sorbent Composed of Natural Materials for the Removal of Arsenic From Waters(Izmir Institute of Technology, 2014) Yılmaz, Dilek; Sofuoğlu, Sait CemilA novel sorbent has been developed by immobilizing chitosan onto pumice for As(V) sorption from waters. In order to ensure its functionality, sorption performance was determined by measuring As concentrations in water using hydride generation atomic absorption spectrometry. The success of the immobilization was checked with characterization techniques as scanning electron microscopy, thermal gravimetric analysis, and elemental analysis. Points of zero charges were determined with potentiometric mass titration. Batch type equilibration studies showed that the sorbent can be employed at a wide pH range resulting in quantitative sorption (>90%) at pH 3.0-7.0, and greater than 70% sorption at pH>8.0. These results demonstrate the advantage of immobilizing chitosan onto pumice, because, under the same conditions, pumice displays <20% sorption towards As(V) whereas chitosan gives approximately 90% sorption but only at pH 3.0. The validity of the method was verified through the analysis of ultra-pure, bottled drinking, and tap water samples spiked with arsenate; the respective sorption percentages of 93.2 (±0.7), 89.0 (±1.0), and 80.9 (±1.3) were obtained by batch type equilibration. The sorbent was applied in a column for the spiked samples of ultra-pure and tap water. Similar sorption percentages (60% at the 18th fraction) were obtained for ultra-pure water whereas the methodology gave more efficient results for tap water (90% at the 20th fraction) demonstrating the potential of the sorbent for an efficient water treatment system. Arsenic sorption was also examined in the presence of common interfering ions resulting in competing effects of PO43- and NO3- on As(V) adsorption.Master Thesis Use of Ion Exchange Resins Modified With Zero-Valent Iron for the Sorption/Speciation of Inorganic As(iii) and As(v) in Waters(Izmir Institute of Technology, 2012) Bölek, Deniz; Eroğlu, Ahmet EminArsenic is a cumulative toxic element and according to Environmental Protection Agency its maximum admissible concentration is established as 10.0 μgL-1 in drinking water. The consumption of arsenic via drinking contaminated water causes chronic and acute poisoning which result in different cancer types. Therefore, determination, speciation and removal of arsenic compounds from waters are important. This study aims to develop a novel sorbent for removal of inorganic arsenic species from contaminated waters. For this purpose a strong anion exchange resin (Amberlite IRA 458) was modified with zero valent iron (ZVI). In the first part of the study, various commercial anion exchange resins and novel resins prepared in the study were used for sorption and speciation of inorganic arsenic. For all the sorbents, the optimized sorption parameters were determined to be 25 ËšC for sorption temperature, 50.0 mg for sorbent amount, 60 min for shaking time for 20.0 mL of 100.0 μgL-1 of arsenic species. The release of As(III) and As(V) from the sorbents was realized using two eluents, 2% (m/v) NaOH + 3% (m/v) NaCl and 5% (m/v) NaOH + 3% (m/v) NaCl, respectively. The accuracy of the proposed methodology was verified with sorption studies for various water types spiked with 100.0 μgL-1 As(III) and As(V). Sorption values of ZVI-IRA 458 were determined to range between 59.1% and 100% for As(III) and between 61.5% and 100% for As(V). Moreover, the sorption efficiencies of the novel sorbents were compared with those of the commercial sorbents.In the final part of the study, the sorption results demonstrated that the most effective immobilization method was NaBH4 reduction and the most efficient resin to be modified was Amberlite IRA 458. Also, the sorption characteristic of ZVI-modified resins showed that the removal efficiency depended on the type of resins and arsenic species in water.Master Thesis Separation of Trace Antimony and Arsenic Prior To Hydride Generation Atomic Absortion Spectrometric Determination(Izmir Institute of Technology, 2005) Yersel, Müşerref; Eroğlu, Ahmet EminA separation method utilizing a synthetic zeolite (mordenite) was developed in order to eliminate the gas phase interference of Sb(III) on As(III) during quartz furnace hydride generation atomic absorption spectrometric (HGAAS) determination. The efficiency of the proposed separation method in the reduction of suppression effects of several metal ions on As(III) signal was also investigated. Among the volatile hydride forming elements and their different oxidation states tested (Sb(III), Sb(V), Se(IV), Se(VI), Te(IV), and Te(VI)), only Sb(III) was found to have a signal depression effect even at low (µg l-1) concentrations under the experimental conditions employed. It has been shown that mordenite adsorbs Sb(III) quantitatively, even at a concentration of 1000 µg l-1, at pHs greater than 2, and also, it reduces the initial concentrations of the metal ions to lower levels which can be tolerated in many studies. The adsorption of Sb(III) on mordenite follows the Freundlich isotherm and is endothermic in nature.