Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Year-To Differentiation of Black Tea Through Spectroscopic and Chemometric Analysis(01. Izmir Institute of Technology, 2024) Yorulmaz, Hilal; Özen, Fatma BanuBu çalışmada, hasat yılının siyah çayın çeşitli spektral profilleri üzerindeki etkisi incelenerek, iki hasat yılından siyah çay örneklerinin ayırt edilmesi amaçlanmıştır. Her metodolojinin avantajlarından yararlanılarak, orta kızılötesi, UV-görünür ve floresan spektroskopisinin yetenekleri, çok değişkenli istatistiksel yöntemlerle birlikte kapsamlı bir şekilde incelenmiştir. Değişen iklim koşulları ve mevsimsel döngüler nedeniyle, çay gibi gıda ürünlerinin bileşimi bir hasat yılından diğerine daha değişken hale gelmiş ve genel ürün kalitesini etkilemiştir. Bu nedenle, 2021 ve 2022'de hasat edilen 205 çay örneğini incelemek için orta kızılötesi, UV-görünür ve floresan spektroskopisi kullanılmıştır. Orta kızılötesi spektrumlar hem demlenmiş hem de toz örnek formları için toplanırken, yalnızca demlenmiş örnekler diğer spektroskopik yöntemler kullanılarak analiz edilmiştir. Örnekleri hasat yılına göre sınıflandırmak için PLS-DA, OPLS-DA ve SIMCA modelleri geliştirilmiştir. Orta kızılötesi verilere dayanan modeller toz örnekler için %93,33 ve aşılanmış örnekler için %90,33 doğru sınıflandırma oranlarına ulaşmıştır. Ek olarak, floresan ve UV-görünür spektral veriler sırasıyla %98,3 ve %100 başarı oranlarıyla oldukça doğru sonuçlar vermiştir. SIMCA diğer çok değişkenli yöntemlerle karşılaştırıldığında daha düşük performans gösterse de bulgular spektroskopik tekniklerin kemometrik yaklaşımlarla entegre edilmesinin siyah çayı farklı yıllarda etkili bir şekilde izleyebileceğini böylece, çay üretiminde kalite kontrol ve sınıflandırma süreçlerinin iyileştirilmesine katkıda bulunabilir.Master Thesis Determination of Coloring Substances in Cleaning Products by Chemometrics Methods(01. Izmir Institute of Technology, 2024) Töremen, Çetin; Özdemir, DurmuşBu tez çalışmasında yüzey temizleyici örnekleri incelenmiştir. Bu numunelerin içerisine çeşitli konsantrasyonlarda belirlenen boya miktarları eklenerek hazırlanan numunelere UV-Görünür Bölge Spektrofotometrisi uygulanmıştır. Kısmi en küçük kareler (PLS), basit en küçük kareler regresyonu (SLR) ve genetik ters en küçük kareler (GILS) yöntemleri, bu renklendirici maddelerin kantitatif tayini için hazırlanan numunelerin görünür spektrumlarına başarıyla uygulanmıştır. Bu boyaların ve tek boya içeren temizlik ürünlerinin ikili ve üçlü karışımları halinde toplam 35 adet numune hazırlandı. Bu 35 örnekten 29 tanesi kalibrasyon seti olarak seçilmiş, geri kalan 6 tanesi ise bağımsız validasyon seti olarak kullanılmıştır. Hazırlanan sete 400-700 nm aralığındaki absorpsiyon spektrumları kaydedilerek elde edilen spektral verilere SLR, PLS ve GILS yöntemleri uygulanarak ortaya çıkan tahminler gerçek değerlerle karşılaştırıldı. Bu yöntemlerin (PLS ve GILS) regresyon katsayıları (R²) ve standart hata çapraz doğrulama (SECV) değerleri ile tahminin standart hatası (SEP) bulunmuş, sonuçlar değerlendirilmiş, kemometrik modellemenin doğruluğu gözden geçirilmiş, tahminler ve referanslar karşılaştırıldı. Bu analiz yöntemleri ile kemometrik yöntemlerin UV-Görünür Spektroskopi ile birleştirilmesiyle temizlik ürünlerindeki boyaların konsantrasyonu belirlenebilmektedir.Master Thesis Development of Chemometrics Method Based on Infrared Spectroscopy for the Determination of Cement Composition and Process Optimization [master Thesis](01. Izmir Institute of Technology, 2021) Tepeli, Dilek; Özdemir, DurmuşCalcium, silicon, aluminum, iron oxide-containing raw materials are used in controlled portions to manufacture cement. (How cement Is Made, n.d.) This mixture is first converted to clinker, obtained by heating the mixture to 1500oC; some additives are added and ground to obtain cement. Depending on the purpose, various types are produced, and therefore, the determination of cement composition is an essential task for the quality consideration and the sustainability of the production processes. The quantitative analysis of cement is performed with X-ray fluorescence spectroscopy. However, XRF generally requires tedious and lengthy analysis times. In this study, quantitative determination of the raw materials, intermediate products, and types of cement by using Fourier transform infrared spectroscopy coupled with chemometrics multivariate calibration method is aimed, which could be an alternative for the current XRF technique. Samples were collected from a local cement factory that has been in the sector for several years. Reference analyses of the samples were performed at the quality control laboratory of the same factory. The same samples were analyzed by the FTIR-ATR spectrometer. The resulting FTIR spectra combined with XRF reference composition data were used to construct calibration models using the partial least squares method (PLS). Based on the obtained results, the proposed method could generate quite successful results for the quantitative determination of all types of products used to produce cement. The regression coefficients (R2) of the PLS models vary from 0.95 to 0.99. The standard errors of cross-validations were found as from 0.21 to 1.42 (w/w%).Master Thesis Development of Molecular Fluorescence Spectroscopy Based Multivariate Calibration Models for Quantitative Determination of Fatty Acids and Triacylglycerol Compositions of Olive Oils(01. Izmir Institute of Technology, 2020) Hedef, Onur; Özdemir, DurmuşThis study illustrates the quantitative determination of fatty acid and triacylglycerol composition of olive oils by using multivariate calibration methods namely partial least squares (PLS) and genetic inverse least squares (GILS) coupled with molecular fluorescence spectroscopy. The reference analysis of the olive oils was carried out with gas chromatography (GC) and high-performance liquid chromatography (HPLC) for the compositions, respectively. A total of 125 olive oil samples were collected from Marmara and Aegean olive growing regions in western Turkey, right after the olives oils are produced in the 2010 -2011 season. Chromatographic and fluorescence analyses were performed simultaneously on the samples and then collected spectra were combined with reference analysis results for the multivariate calibration step. Among the several components analyzed by both GC and HPLC, 10 components from fatty acids and 10 components from triacylglycerols were chosen for modeling. Multivariate calibration models were constructed by randomly selecting 100 samples as calibration set and assigning the remaining 25 samples to the independent validation set using PLS and GILS with leave one out cross-validation based on the fluorescence spectra of the olive oils. The results have demonstrated that the compositions could be successfully determined by using molecular fluorescence spectroscopy. The standard error of cross-validation (SECV) and standard error of prediction (SEP) values were acceptable for most of the components. The regression coefficients (R2) of reference values vs. predicted values ranged from 0.70 to 0.98, indicating that molecular fluorescence spectroscopy combined with multivariate calibration could potentially be used for quantitative determination.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, DurmuşPersonal 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, DurmuşPolyethylene 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, DurmuşA 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 On the Pathway of Whole Blood Analysis by Portable Atr-Ir and Chemometrics(Izmir Institute of Technology, 2017) Koç, Mert; Karabudak, EnginCurrently, the number of patients per state hospital in Turkey is too high. Doctors need point of care(PoC) tests like blood analysis, to diagnose his/her patients. Patients is firstly examined by a doctor. If the doctor needs blood analysis, then patient gives blood to blood laboratory. After a certain time, the results are given to the patient and he/she meets with the doctor again to show the results. This causes too much time loss. In addition, these analyses are not performed in some small healthcare centers and cause extra time loss, which is another major problem in the health care system. Electrochemical, spectrophotometric and enzymatic analysis methods are mostly used for blood analysis. The sum of glucose, urea, triglycerides, cholesterol, albumin and total protein tests cost for 7TL. Blood samples are taken separately about 2-5ml volume for each test and preliminary procedures are required. On the other hand, ATR-IR spectrometry is a technique that does not require preliminary sample preparation, less sample volume, cheap and results in shorter time. Studies have been carried out in the literature which have shown positive results on glucose, urea, triglycerides, cholesterol, albumin and total protein in blood, plasma and serum using ATR technique. The six components in blood have importance in the diagnosis of a disease at the patient. The aim of this thesis is a preliminary study to determine the glucose, urea, triglyceride, cholesterol, albumin and total protein concentrations in 1 minute, 1 u of blood, using disposable crystals and less than 1 dollar in the doctor's room by direct analysis of the blood using ATR-IR spectrometry and using chemometrics algorithms to predict them from the spectral data.Master Thesis Chemical Characterization of Olive Oils From Karaburun Peninsula(Izmir Institute of Technology, 2014) Uncu, Oğuz; Özen, Fatma BanuChemical characteristics of olive oils produced from Erkence olive variety that is mainly grown around Karaburun Peninsula of İzmir have not been investigated thoroughly although this variety has high oil content and ripens earlier compared to other olive types. Identifying the chemical characteristics of olive oils could be useful to obtain geographical indication labelling for olive oils produced from this variety. Aim of this study is to determine some important chemical characteristics of olive oils from Erkence olive variety produced in Karaburun region and to investigate the differences in olive oils that come from various parts of the Peninsula using chemometric techniques as principal component analysis (PCA) and partial least square (PLS) regression. For this purpose, total phenolic content, fatty acid profile, phenolic profile, total carotene and chlorophyll contents and oxidative stability of 64 olive oils were determined. FTIR spectra for these oils were also evaluated. According to PCA results, classification with respect to geographical origin was relatively more successful with FTIR analysis while phenolic and fatty acid profiles did not result very satisfactory separation between regions. Moreover, FTIR spectra and various chemical parameters were used to predict oxidative stability of all olive oil samples. Oxidative stability was predicted successfully from IR spectra whereas prediction from chemical parameters was not that successful. IR spectra were also used to predict various chemical parameters. As a result of PLS regression; chlorophyll and carotenoid, some individual phenolic components (pcoumaric, hydroxtyrosol) and some major fatty acids (oleic, linoleic and palmitic) were predicted.Master Thesis Chemometric Studies for Classification of Olive Oils and Detection of Adulteration(Izmir Institute of Technology, 2008) Gürdeniz, Gözde; Özen, BanuThe aim of this study is to classify extra-virgin olive oils according to variety, geographical origin and harvest year and also to detect and quantify olive oil adulteration. In order to classify extra virgin olive oils, principal component analysis was applied on both fatty acid composition and middle infrared spectra. Spectral data was manipulated with a wavelet function prior to principal component analysis. Results revealed more successful classification of oils according geographical origin and variety using fatty acid composition than spectral data. However, each method has quite good ability to differentiate olive oil samples with respect to harvest year.Middle infrared spectra of all olive oil samples were related with fatty acid profile and free fatty acidity using partial least square analysis. Orthogonal signal correction and wavelet compression were applied before partial least square analysis.Correlation coefficient and relative error of prediction for oleic acid (highest amount fatty acid) were determined as 0.93 and 1.38, respectively. Also, partial least square regression resulted in 0.85 as R2 value and 0.085 as standard error of prediction value for free fatty acidity quantification.In adulteration part, spectral data manipulated with principal component and partial least square analysis, to distinguish adulterated and pure olive oil samples, and to quantify level of adulteration, respectively. The detection limit of monovarietal adulteration varied between 5 and 10% and R2 value of partial least square was determined as higher than 0.95. Hazelnut, corn-sunflower binary mixture, cottonseed and rapeseed oils can be detected in olive oil at levels higher than 10%, 5%, 5% and 5%, respectively.