Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Fabrication of Polymer Nanofiber / Poly (3,4 Ethylene Dioxythiophene) / Metal Particle Hybrid Composite for Volatile Organic Compound Sensing Applications(Izmir Institute of Technology, 2020) Acar, İrem; Yıldız, Ümit HakanThis study aims to produce polymer nanofiber / poly (3, 4 ethylene dioxythiophene) / metal particle hybrid composite as a bioelectronic interface for the detection of volatile organic compounds in human breath. The sensor platform consists of two layers: polymeric nanofiber structure and conductive layer. Polyurethane (PU), polycaprolactone (PCL) and poly L-lactide-co-?-caprolactone (PLLCL) were selected to form polymeric nanofibers with electrospinning. For electrospinning process, solutions of polyurethane (PU) (25wt%) in DMF, polycaprolactone (PCL) (20wt%) in DCM (4) -DMF (1) and poly L-lactide-co-?-caprolactone (PLLCL) (10wt%) in DCM (9) -DMF (1) are prepared. PU, PCL and PLLCL polymer solutions are subjected to 25 kV, 29kV and 25 kV electrical potential, respectively, to produce electrospinning fibers. Poly(3,4-ethylenedioxythiophene) (PEDOT) and multi-walled carbon nanotubes (MWCNTs) are used to produce conductive layers on PU, PCL and PLLCL polymer nanofibers. The produced sensor platforms are tested by the electrochemical station, which records the electrical current change over time. The sensing mechanism is assumed to be the adsorption of VOCs to the conductive PEDOT and CNT layer, thus blocking the electron current on the PEDOT and CNT network and causing resistance change. More clearly; swelling of the polymer structure in the sensor causes destruction in the upper layer and micro-dimensional cracks in the PEDOT and CNT network, increasing resistance to electron flow and decreasing current. Organic volatile compounds (acetone, toluene, ethanol, isopene etc.) are detected from ppm to ppb range and reproducible and reliable responses are recorded.Master Thesis Design and Synthesis of Bodipy Based Phosgene Sensor(Izmir Institute of Technology, 2018) Sayar, Melike; Emrullahoğlu, MustafaPhosgene was used in World War I as a chemical warfare agent and now, it is used as only a chemical intermediate in the industrial field according to laws. Because of the result of exposure to phosgene, its detection plays a significant role to protect civilians against terrorist attacks, and also to warn people if there would be any leakage in industrial facilities. To determine the phosgene, there are several methods like gas chromatography, which has several disadvantages such as poor portability and sensitivity and high cost or requiring of sophisticated procedures. However, fluorescence analysis has high sensitivity, resolution, and simplicity which provides real-time visual detection of analytes. For this thesis, boron-dipyrromethene (BODIPY) dye was used as the signal reporter by synthesizing the new BODIPY derivative, to benefit from its outstanding photophysical properties. In addition to that, as the main purpose of this thesis, this is the first time an o-aminobenzyl amine group was used due to be the phosgene-specific reactive motif for research in phosgene sensing which is an investigation of photophysical properties of designed BODIPY derivative in the absence and presence of phosgene.Master Thesis A Chromatographicstudy of Carbon Monoxide Adsorption in Clinoptilolite(Izmir Institute of Technology, 2001) Narin, Güler; Ülkü, SemraAdsorption equilibrium and kinetic parameters for CO/clinoptilolite adsorbate/adsorbent pair were determined by perturbation gas chromatography. Chromatographic experiments were performed at temperatures in the 60-120°C range and at carrier gas flow rates in the range of 10.31-24.36 em/sec. The chromatographic response peaks were obtained by concentration pulse method. A packed column of 10 em length and 0.46 em inlet diameter which was packed with clinoptilolite particles with narrow size distribution (500-850 §) around mean diameter of301.9 § was used. The clinopti10lite particles were excavated from Gordes, Western Anatolia. The moments of the response peaks were calculated by integration of experimental chromatographic data and matched to the .model parameters in order to determine the equilibrium constants and diffusion coefficients. The dynamic model (Haynes and Sarma, 1973) was applied to describe the adsorption and diffusion processes in the packed column. This model includes axial dispersion, external mass transfer resistance, micropore and mesopore diffusion resistances. The equilibrium constants (Henry's law constants, K) were calculated in the range of 40 - 952 and were found to be in good agreement with the results in the literature. These constants were found to decrease with increasing temperature. The heats of adsorption were obtained in the range of 54.15 - 57.14 kl/mol from the slope of van't Hoff plots and compared with those in the literature. The heats of adsorption were found to be lower than those reported in the literature obtained for the same adsorbate/adsorbent pair. The higher heats of adsorption were explained by the smaller pore size, higher cation content of the clinoptilolite and more accessibility of the cations in the clinoptilolite framework by CO molecules. Heats of adsorption remained almost constant over the carrier gas velocity range studied. The contributions of axial dispersion and other mass transfer resistances Indiffusion of CO in clinoptilolite were also determined. The total dispersion exhibited slight change (average 0.035 see) with temperature implying that the micropore diffusional resistance was not dominant for diffusion of CO in clinoptilolite under the experimental conditions studied. The axial dispersion coefficient was determined in the range of 1.149.88 cm2/sec and the total mass transfer resistances were found between 0,02-0.06 sec. The results showed that the mesopore diffusion resistance was the controlling mechanism in CO diffusion in clinoptilolite. Mesopore diffusion coefficient was estimated as 2.98xlO-3 cm2/sec. This value was in good agreement with the theoretically determined value.Master Thesis Investigation of Dichlorvos (ddvp) and Trifluralin Pesticide Levels in Tahtalı Dam Water(Izmir Institute of Technology, 2002) Erdoğan, Murat; Özgen, TamerkanIn this study, dichlorvos (Dimethyl 2,2-dichlorovinyl phosphate - DDVP) and trifluralin (.,.,.-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidin) pesticide concentration levels in Tahtalı Dam Water were investigated. Dichlorvos is an organophosphorus pesticide, whereas Trifluralin is a dinitroaniline pesticide.Both of these pesticides are widely used for agricultural purposes in Tahtalı Dam Basin. These pesticides could be carried to the Tahtalı Dam Water, and therefore their concentrations should be controlled.Another reason why these pesticides were selected was that, their method of determination was not straightforward and special determination technique has to be used. That is why these pesticides were not studied extensively for İzmir area.For the determination of the above-mentioned pesticides, gas chromatographymass spectrometry (GC-MS) was generally preferred as reported in most papers [1,2,3].The GC-MS instrument in our laboratory has an Ion Trap (IT) mass detector. Operating in Selected Ion Storage (SIS) or Tandem mass (MS-MS) modes can increase the sensitivity and selectivity of this instrument. The matrix effect coming from the aqueous solution was eliminated by GC-SIS-MS and GC-MS-MS. The detection limits of the instrument are 0.8 .g/L for trifluralin and 10.5 .g/L for dichlorvos, therefore a preconcentration process was required because the studied concentrations are in 1-3 .g/L levels for surface water and 0.1 .g/L levels for drinking water.Liquid-Liquid Extraction (LLE) and Solid Phase Extraction (SPE) methods were used for sample preconcentration. Gas chromatography (GC) - Mass spectrometry (MS) and Tandem mass spectrometry (MS.MS) were employed for the identification and quantification of Trifluralin and Dichlorvos (DDVP) pesticides. For Solid Phase Extraction procedure ENVI-18 Disk was used, optimizing the extraction volume, pH and the salt concentration. Liquid-Liquid extraction procedure was also used, optimizing the extraction volume. In GC.MS.MS, the lowest detectable concentrations for the Trifluralin and Dichlorvos were found as 0.8 ng/L and 10.5 ng/L, respectively.Recovery of Dichlorvos for Liquid-Liquid Extraction and Solid Phase Extraction were 86.0 (±5.4) % and 63.0 (±5.7) % in water samples spiked with 200 ng/L pesticides.Recovery of the Trifluralin for Liquid-Liquid Extraction and Solid Phase Extraction were 90.8 (±9.4) % and 107.5 (±4.5) % in water samples spiked with 200 ng/L pesticides.Water samples, which were collected between 01 June 2002 to 30 September 2002 by İZSU (İzmir Büyükşehir Belediyesi Su ve Kanalizasyon Genel Müdürlüğü), were analyzed using GC-MS system with tandem mass (MS-MS) mode after preconcentration process. Analysis of samples showed no detectable Trifluralin and Dichlorvos levels in Tahtalı Dam Water.Master Thesis Chromatographic Determination of Glycoalkaloids in Eggplant(Izmir Institute of Technology, 2006) Tek, Neslihan; Tek, Neslihan; Eanes, Ritchie C.Novel modifications were applied to high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) for the separation and quantitation of the steroidal glycoalkaloids (SGAs) solanine, chaconine, solamargine, and solasonine as well as the steroidal glycoalkaloid aglycones (SGAAs) solasodine and solanidine. Because attempts to develop a gradient elution HPLC method were only marginally successfully and non-robust, it was deemed more practical to develop separate HPLC methods for either the SGAs or SGAAs of interest. Furthermore, a novel approach using methanol as a mobile phase modifier was still required to successfully separate solamargine and chaconine. Comparing potential mobile phase buffers, ammonium dihydrogen phosphate was chosen as the most efficient, stable, and economical. Separations were best realized isocratically at a column temperature of 50 °C for the SGAs and either 26 °C or 50 °C for the SGAAs. Progesterone was applied as an internal standard. Effects of pH were also tested. Figures of merit such as limit of detection (LOD), limit of quantitation (LOQ), and linear dynamic range are described herein. Lastly, solid-phase microextraction (SPME) using on-fiber derivatization coupled with GC-MS was investigated for extraction and analysis of these SGAAs. A carbowax divinylbenzene (CW-DVB) coated SPME fiber was the most suitable. Solanidine could be extracted and identified directly using our SPME/GC-MS method while solasodine required a derivatization step involving trimethylsilylimidazole (TMSI). Although initial attempts were qualitatively reproducible, eventual degradation to fibers precluded complete study. Cholesterol as an internal standard was investigated.Master Thesis Investigations on Aroma Profile of Artisanal Yoghurt Starter Cultyres(Izmir Institute of Technology, 2012) Baran, Ezgi; Harsa, Hayriye ŞebnemYoghurt is an important fermented milk product that is consumed widely around the world as a part of the diet. Yoghurt is produced by lactic acid fermentation using Streptococcus thermophilus, and Lactobacillus delbrueckii ssp. bulgaricus. The most important criteria in yoghurt production are the selection of artisanal yoghurt starter cultures to achieve the typical aroma and quality of the final product. The typical aroma of yoghurt is identified chiefly by acetaldehyde that is the most important for yoghurt aroma. The aim of this study is to determine artisanal yoghurt starter cultures that provide the most desirable aroma to yoghurt, in order to promote industrial production with such flavor. In the first part of this study, the influence of different aroma cultures addition on the aroma production properties in yoghurt products was investigated. Nine different aroma cultures were added into the starter culture combinations at two different inoculation ratios. Among all of the combinations, just one yoghurt combination was selected according to the highest acetaldehyde and also the highest sensory scores. According to the results, two batches of yoghurt were produced: Sample 1 containing only yoghurt starter cultures (Lactobacillus bulgaricus Y30 + Streptococcus thermophilus Y24), was used as control yoghurt; Sample 2 containing yoghurt starter cultures plus with selected aroma culture (P10), was used as yoghurt with aroma culture. Yoghurt samples were stored at 4 °C for 21 days. The pH, titratable acidity, total solids, fat, protein, syneresis, viscosity, aroma profile, lactic acid and lactose profile, proteolytic activity, microbiological characteristics and sensory characteristicsMaster Thesis Development of Chemometric Multivariate Calibration Models for Spectroscopic Quality Analysis of Biodiesel Blends(Izmir Institute of Technology, 2011) Bağcıoğlu, Murat; Özdemir, Durmuş; Özdemir, DurmuşThe fact that the biodiesel is produced from renewable resources and environmentally friendly when compared to the fossil-based petroleum diesel, biodiesel has gained an increasing interest. It is mainly produced from a variety of different animal fat and vegetable oil combined with an alcohol in the presence of a homogeneous catalyst and the determination of the quality of the produced biodiesel is as important as its production. Industrial scale biodiesel production plants have been adopted the chromatographic analysis protocols some of which are standard reference methods proposed by official bodies of the governments and international organizations. However, analysis of multi component mixtures by chromatographic procedures can become time consuming and may require a lot of chemical consumption. For this reason, as an alternative, spectroscopic methods combined with chemometrics offer several advantages over classical chromatographic procedures in terms of time and chemical consumption. With the immense development of computer technology and reliable fast spectrometers, new chemometric methods have been developed and opened up a new era for processing of complex spectral data. In this study, laboratory scale produced biodiesel was mixed with methanol, commercial diesel and several different vegetable oils that are used to prepare biodiesels and then several different ternary mixture systems such as diesel-vegetable oil-biodiesel and methanol-vegetable oil-biodiesel were prepared and gas chromatographic analysis of these samples were performed. Then, near infrared (NIR) and mid infrared (FTIR) spectra of the same samples were collected and multivariate calibration models were constructed for each component for all the infrared spectroscopic techniques. Chemometric multivariate calibration models were proposed as genetic inverse least square (GILS) and artificial neural networks (ANN). The results indicate that determination of biodiesel blends quality with respect to chemometric modeling gives reasonable consequences when combined with infrared spectroscopic techniques.Master Thesis Spectroscopic Determination of Industrial Oil Blends Using Multivariate Calibraton(Izmir Institute of Technology, 2009) Yalçın, Ayşegül; Özdemir, DurmuşThis study focuses on the development of multivariate calibration models for the aluminum rolling oil additives and contaminants using Fourier Transform Infrared (FTIR) spectroscopy and a genetic algorithm based inverse least squares (GILS) method. Multivariate calibration models were generated for both synthetic mixtures and real process samples taken from an industrial aluminum production plant. Two different additives and six different suspected contaminants were investigated in the base oil lubricant. Gas chromatography (GC) was used for the analysis of real process samples in order to establish reference values of additives and contaminants in the base rolling oil. FTIR spectra of real samples together with the reference values established with GC analysis were used to generate multivariate calibration models. GC analysis revealed that most of the contaminants gave overlapped chromatograms and therefore only the total contamination was determined with reference GC analysis. On the other hand, FTIR spectroscopy coupled with multivariate calibration was able to resolve overlapping components with synthetic samples. The reference values for both additives and contaminants obtained by GC were compared with the results of the spectroscopic analysis. The multivariate calibration models based on spectroscopic data validated with the real process samples in a period of twelve months, however only a set of 3-month data is given in this thesis. The R2 values between GC and multivariate spectroscopic determinations were around 0.99 indicating a good correlation between the two methods.