Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
Browse
15 results
Search Results
Master Thesis The Development of Chemometric Methods Based on Molecular Spectroscopy for the Standardization of Production Processes and Product Traceability of Personal Care and Cleaning Products(Izmir Institute of Technology, 2019) Çiftçi İlmek, Berfu; Özdemir, Durmuş; Özdemir, Durmuş; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of TechnologyPersonal care and cleaning products are the main consumer goods. Changes in our heath caused by all of the chemicals that we exposed to everyday if these products are not produced according to the regulations and determined formulations. Because of this reason, quality control of the product formulation quantitatively is very important. There are some analytical methods for the determination of anion active matter, nonionic matter and total active matter in the product mixture. However, these techniques are expensive and do not give accurate results. The purpose of this thesis principally based on development of rapid, accurate and practical infrared spectroscopic technique based on multivariate chemometrics data analysis methods for the standardization of production processes and product traceability of personal care and cleaning products. In this thesis, two different products are studied which are namely liquid soap and shower gel. Fourier Transform Infrared spectroscopy coupled with Attenuated Total Reflectance accessory based chemometrics multivariate calibration models were developed for the quantitative determination of liquid soap and shower gel compounds. Genetic Inverse Least Squares was used as the chemometrics method for the development of multivariate calibration models in the quantitative determination of liquid soap and shower gel compositions. Standard error of cross validation and standard error of prediction values for content of the liquid soap samples were found 0.26% and 0.21 % (w/w %), respectively. Standard error of cross validation and standard error of prediction values for content of the shower gel samples were found 0.27 % and 0.30 % (w/w %), respectively.Master Thesis Determination of Total Acid Number in the Optimization of Oleate Production by Using Fourier Transform Infrared Spectroscopy and Multivariate Calibration(Izmir Institute of Technology, 2019) Toygar Türkün, Nihan; Özdemir, Durmuş; Özdemir, Durmuş; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of TechnologyPolyethylene glycol oleate (PEG-Oleate) is a non-ionic surfactant, and is an important emulsifier for water-oil systems. It is produced by reacting oleic acid and polyethylene glycol (PEG) under vacuum for around 4 hours and at 160 °C, in the presence of acid catalyst which is para toluene sulfonic acid (PTSA). The quality and process control of this production is determination of total acid number (TAN) by the standard method ASTM D974 which is a color indicator titration. Although titration is a simple method, it is relatively time consuming and prone to human error. Besides, the solvents used in titration method, are significantly unhealthy for humans. The aim of this study is to develop fast and simple procedure for the determination of total acid number based on Fourier Transform Infrared Spectroscopy (FTIR) combined with multivariate calibration methods namely Genetic Inverse Least Squares (GILS) and Partial Least Squares (PLS). The reference total acid number of the samples collected during the esterification reaction, had been carried out by the ASTM D974 standart method and the Fourier Transform Infrared (FTIR) spectra of the same samples were also collected simultaneously with single reflection diamond Attenuated Total Reflectance (ATR) accessory. Univariate calibration was applied on a specific wavenumber corresponding to the ester peak around 1739 cm–1. Although the changes in the ester peak was showing an inrease associated to the esterification of the reactants, the results of the univariate calibration was unsucsesful. The best regression coefficient was found to be 0.997 by GILS method along with SECV and SEP as 2.295 and 2.694 mg KOH/g, respectively. The results of GILS showed that it is possible to monitor esterification process of PEG oleate.Master Thesis Development of Chemometric Calibration Toolbox and Its Application for Determination of Slep Adulteration(Izmir Institute of Technology, 2018) Akkoç, Gün Deniz; Özdemir, Durmuş; Özdemir, Durmuş; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of TechnologyA chemometric calibration toolbox, which contains Inverse Least Squares (ILS) regression, Principle Components Regression (PCR), Partial Least Squares Regression (PLSR), Genetic Inverse Least Squares (GILS) regression, and Ridge regression, was developed in MATLAB environment. During the development, multiple strategies to improve the calculation speed, namely vectorization and parallelization, were employed. Besides these programmatic strategies, efficient cross-validation (CV) procedures were implemented that are specifically tailored for parameter tuning of PCR and PLSR. For GILS, by constructing CV matrices in advance, the computational cost was further reduced. Additionally, a Graphical User Interface (GUI), which also includes baseline correction and variable range selection capabilities, was developed. For increased convenience, regardless of the chosen model, the toolbox returns a single vector of regression coefficients that accounts for centering and scaling of variables along with variable selection. Using the developed toolbox, quantitative determination of salep adulteration was carried out through chemometric calibration methods on Mid-IR data obtained from FTIRATR which is a fast and easy-to-use spectroscopic instrument. The main motivation was the lack of an established method for determination of adulteration of salep which can be quite common due to very high price of pure salep, despite the strict legal regulations. Using 365 samples covering a wide range of adulteration scenarios with 20 adulterants, calibration models were obtained and evaluated. Ensemble model, obtained by averaging GILS and Ridge, yielded the best RMSEP of 6.82 (w/w %). To cope with the unspecific adulterant problem, SIMCA was employed to provide an qualitative insight about the presence of such compounds.Master Thesis Development of Fast and Simple Analytical Methods for the Determination of Honey Adulteration and Forgery Based on Chemometric Multivariate Data Analysis by Using Molecular Spectroscopy(Izmir Institute of Technology, 2016) Başar, Başak; Özdemir, Durmuş; Özdemir, Durmuş; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of TechnologyHoney is one of the most valuable and expensive nutrition due to its health effects on human body. In recent years, honey adulteration has become an important problem and is a subject of many publications. There exists various analytical methods for determination of honey adulteration with 13C/12C isotope ratio mass spectrometry (IR-MS) being the most common. However, one of the recent studies indicates that different honey types depending on geographical and botanical origin may have significantly different 13C/12C isotope ratios rendering this method questionable. Thus, development of an analytical method for qualitative and quantitative determination of forgery and adulteration of honey without tedious and complicated sample preparation while being relatively simple and fast new analytical methods became a must. In this study, Fourier Transform Infrared spectroscopy coupled with Attenuated Total Reflectance and Fourier Transform Near Infrared spectroscopy based chemometrics multivariate calibration models were developed for the quantitative determination of honey adulteration. To simulate adulteration scenarios, artificially adulterated honey samples were prepared by adding beet sugar, corn syrup, glucose and sucrose with various concentrations to pure honey samples. Two different multivariate calibration methods namely Genetic Inverse Least Squares and Partial Least Squares were used and the applicability of these methods have been evaluated with an independent validations and test set composed of FTIR spectra of more than 100 pure honey samples along with the adulterated samples. Standard error of cross validation and standard error of prediction values for honey content of the samples were found 2.52% and 2.19% (w/w %), respectively.Master Thesis Development of a New Infrared Spectroscopic Method Based on Multivariate Calibration for the Determination of Aluminum and Magnesium Oxid Thickness on Aluminum Foil and Sheets Surfaces(İzmir Institute of Technology, 2016) Meşe, Ayten Ekin; Özdemir, Durmuş; Özdemir, Durmuş; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of TechnologySurface oxidation is a general problem for certain industrial applications such as coating and painting of the finished rolled products. A detailed understanding for the oxide growth mechanism as well as the development of a simple analytical method to measure this oxide thickness is very important in aluminum rolling industry and this study aims to develop a spectroscopic method to determine the oxide thicknesses on the surface of the aluminum by using multivariate calibration and infrared spectroscopy. Two main series of different aluminum alloys (3005 and 3003BZ) were selected in this study to develop a proposed methodology which is based on the combination of Fourier Transform Infrared Spectroscopy (FTIR) with Grazing Angle ATR accessory and chemometrics multivariate calibration techniques. In order to obtain oxide thickness values, X-ray Photoelectron Spectroscopy (XPS) was used and aluminum oxide (Al2O3) and magnesium oxide (MgO) thicknesses determinations were carried out by two different multivariate calibration models which are Genetic Inverse Least Squares (GILS) and Genetic Partial Least Squares (GPLS). These models were able to predict Al2O3 and MgO thicknesses using FTIR that is faster, easier and cheaper to operate as well as from XPS. The correlation coefficients of XPS reference oxide thickness values versus FTIR-GATR based GILS and GPLS predicted values were better than 0.919 in range of 0 to 25 nanometers for Al2O3 and 0 to 35 nm for MgO. These results suggest that grazing angle FTIR-ATR spectroscopy may offer a simple and nondestructive alternative for quick determination of oxide layer thickness.Master Thesis Development of Rapid and Simple Spectroscopic Techniques Based on Chemometrics Data Analysis for the Determination of Goat Milk Adulteration With Cow Milk(Izmir Institute of Technology, 2015) Samancıoğlu, Hülya; Özdemir, Durmuş; Özdemir, Durmuş; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of TechnologyMilk and milk products are one of the most consumed foods. However, there has been an increase in milk adulteration, especially goat milk. Current methods for detection of milk adulteration are expensive, impractical and are not sufficient to answer quantitatively. Therefore, to meet this demand, a rapid, easy to use and inexpensive method was developed in this study. The proposed methodology is based on Fourier Transform Infrared Spectroscopy (FTIR) with the combination of multivariate calibration techniques for determination of adulteration of goat milk with cow milk. During the study, 150 raw goat milk samples were collected from different goats in 3 different seasons (June-2014, December 2014, March2015). Then, adulterated samples were prepared with goat milk, cow milk and water. Both adulterated and raw goat milk samples were analyzed with FTIR. Afterwards, 7 different multivariate calibration models (for each season (3), binary combination of seasons(3) and a ternary combination of all the seasons) were generated with synthetically prepared samples by using Genetic Inverse Least Squares (GILS) and Partial Least Squares (PLS) methods. These models were used to predict both adulterated and raw goat milk samples in order to evaluate the success of the models. Standard Error of Prediction (SEP) values for goat milk, cow milk and water are 7.9, 6.3 and 4.9 (w/w %), respectively, indicate satisfactory predictions by GILS. On the other hand, PLS models gave SEP values ranging between 6.4 and 12.9 (w/w %).Master Thesis Development of Molecular Spectroscopic Multivariate Calibration Models for the Determination of Fatty Acid and Triachyl Glycerol Compositions of Olive Oils(Izmir Institute of Technology, 2014) Kuday, Esra; Özdemir, Durmuş; Özdemir, Durmuş; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of TechnologyThe determination of fatty acid methyl esters and triachyl glycerol compositions of olive oils by chromatographic methods require not only sample pre treatment carried out but also extend the time of the analysis. Also, chromatographic methods are expensive. Therefore, there is a need for an alternative method. In this study, it is aimed to develop molecular spectroscopic multivariate calibration models for the determination of some of the fatty acid methyl esters and triachyl glycerol compositions of olive oils. For this purpose, 79 olive oil samples from different regions of Turkey (Manisa and Bursa) were collected and scanned with Fourier Transform Infrared spectroscopy equipped with attenuated total reflectance (FTIR-ATR) accessory, Fourier Transform Near Infrared spectroscopy (FTNIR) and Gas Chromatography (GC), High Performance Liquid Chromatography (HPLC). Chromatographic analyses of these samples were done by Olive Oil Research Institute and spectroscopic analyses were done by our group. The data obtained from High Performance Liquid Chromatography (HPLC) was chosen as a reference method for triachyl glycerol compositions and also the data obtained from Gas Chromatography (GC) was chosen as a reference method for fatty acid methyl esters. Also, Genetic inverse least squares (GILS) and Partial least square methods (PLS) were used for multivariate calibration. In conclusion, NIR and FTIR combined with multivariate calibration models can be more advantageous compare to chromatographic methods because of their simplicity and speed. When investigating the results, relatively successful calibration models were obtained from GILS method than PLS method.Master Thesis Prediction of Extractives and Lignin Contents of Anatolian Black Pine (pinus Nigra Arnold. Var Pallasiana) and Turkish Pine (pnus Brutia Ten.) Trees Using Infrared Spectroscopy and Multivariate Calibration(Izmir Institute of Technology, 2008) Karaman, İbrahim; Özdemir, Durmuş; Özdemir, Durmuş; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of TechnologyDetermination of quality parameters such as extractives and lignin contents of wood by wet chemistry analyses takes long time. Near-infrared (NIR) and mid-infrared (MIR) spectroscopy coupled with multivariate calibration offer fast and nondestructive alternative to obtain reliable results. However, due to complexity of multi-wavelength spectra, wavelength selection is generally required. Turkish pine and Anatolian black pine are the most growing pine species in Turkey. Forest products industry has widely accepted use of these trees because of their ability to grow on a wide range of sites and their suitability to produce desirable products. Determination of extractives and lignin contents of wood provides information to tree breeders when to cut and on how much chemical is needed in pulping and bleaching process. In this study, 58 samples of Turkish pine and 51 samples of Anatolian black pine were collected to investigate the correlation between NIR and MIR spectra of these samples and their extractives and lignin contents which were determined with reference methods. Genetic inverse least squares (GILS) was used for multivariate calibration. Standard error of calibration (SEC) values were less than 1.86% (w/w) for lignin and 1.19% (w/w) for extractives whereas standard error of prediction (SEP) values were less than 3.81% (w/w) for lignin and 2.04% (w/w) for extractives. Resulting R2 values for calibrations were larger than 0.8. Classification for Turkish pine and Anatolian black pine samples was performed by genetic algorithm based principal component analysis (GAPCA) and these two pine species were classified by using NIR and MIR spectra.Master Thesis Spectroscopic Determination of Vegetable Oiland Biodiesel in Petroleum Diesel Using Mulitivariate Calibration(Izmir Institute of Technology, 2008) Arıkan, Aysun; Özdemir, Durmuş; Özdemir, Durmuş; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of TechnologyDue to the limited petroleum reserves and pollutant effect of petroleum fuels, the use of alternative fuels has became important in recent years. Diesel is one of the most used petroleum fuel, whose exhaust emissions composed of harmful particles, that pollutes the environment. In this sense, vegetable oils and their esters (biodiesel) are considered environmentally friendly fuels, which reduce hazardous impact of diesel emissions. However, using vegetable oils directly in diesel engines may cause some engine problems due to their high viscosity. The most commonly used way to reduce their viscosity is the converting into biodiesel. Because biodiesel production is expensive and time consuming, diesel may be illegally adulterated with vegetable oils before converting into biodiesel.Diesel may also adulterated with kerosene due to the large price differences. The main impact of this adulteration is increased emissions, which damage the environment. On the other hand, the addition of kerosene may also damage the engine. Because of these reasons, it is important to determine these adulterants illegally present in petroleum diesel. In this study, we have determined the adulteration of diesel with sunflower, canola oil, used frying oil, kerosene, and biodiesel by different molecular spectroscopic techniques combined to genetic inverse least squares (GILS). The results showed that the GILS method is suitable in the fast determination of diesel adulteration with vegetable oils, used frying oil, kerosene, and biodiesel when combined to NIR, FTIR-ATR, and molecular spectroscopic techniques.Master Thesis Multivariate Statistical Optimization of Enzyme Immobilization Onto Solid Matrix Using Central Composite Design(İzmir Institute of Technology, 2013) Arpakcı, Tuğba; Özdemir, Durmuş; Özdemir, Durmuş; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of TechnologyIn recent years, scientist have been used alternative technology in order to increase enzyme stability and also reduce the cost of production of enzyme. Immobilization methods have attracted the attention of scientists due to its advantages in comparison with soluble enzyme or other methods. Immobilization process can be affected by many factors for this reason it is important to optimize the effective factors in order to enhance success of this process. In preliminary studies, Bradford protein assay was used for determination of protein concentration. In order to increase sensitivity and accuracy of this assay, Bradford protein assay was combined with a multivariate calibration methods. Genetic Inverse Least Squares (GILS) and Partial Least Squares (PLS) were used for multivariate calibration. Calibration model was constructed for various concentration of Bovine Serum Albumin (BSA). Standard Error of Calibration (SEC) and Standard Error of Prediction (SEP) were calculated and results of multivariate calibration method were compared with univariate calibration methods and each other. In this study, the bovine serum albumin immobilization studies were carried out. The bovine serum albumin was immobilized on chitosan nanoparticles and effective factors such as chitosan concentration, immobilization time, pH and temperature were optimized by using central composite design (CCD). Central composite design is used to investigate interaction between these parameters and to find the optimum values of effective factors.