Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis In-Depth Investigation of the Effects of Different Preprocessing Strategies on Infrared Spectroscopic Data(01. Izmir Institute of Technology, 2021) Deniz, Elin İlayda; Özdemir, Durmuş; Özdemir, Durmuş; 04.01. Department of Chemistry; 01. Izmir Institute of Technology; 04. Faculty of ScienceWhenever collecting experimental data, they may contain several spurious sources of variability which can hinder the extraction of the desired relevant information so that it is rarely the case that they can be processed as such by chemometrics approaches. In recent years, pre-processing techniques has become an integral part of chemometrics modeling with the purpose of providing better endmodels through fundamental knowledge for Near-Infrared (NIR) users. The aim of pre-processing techniques is to improve success of multivariate regression by reducing undesired physical phenomena in the spectra. This thesis describes the theory of present pre-processing techniques and compares the qualitative and quantitative results of their application. Mean centering, scatter-correction methods and spectral derivatives are the instances of those pre-processing techniques used in this thesis. Those techniques and combinations of them have been applied in order to find the best pre-processing strategy. To be able to observe the results and compare the effects of the applied methods, Partial Least Squares and Genetic Inverse Laast Squares are carried out as multivariate calibration methods. When comparing the calibration results of raw data with pre-processing techniques applied data, decreasement standard eror of prediction (SEP) values observed after appliying those techniques, which is good manner. However, better in comparison, t-Test: Paired Two Sample for Means applied. The results demontrates that there is no significant difference within 95% confidence level.Master Thesis Monitoring the Esterification Reactions of Carboxylic Acids With Alcohols Using Near-Infrared Spectrocopy and Multivariate Calibration Methods(Izmir Institute of Technology, 2003) Öztürk, Betül; Öztürk, Betül; Özdemir, Durmuş; Özdemir, Durmuş; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of TechnologySimultaneous determination of mixtures of alcohols, acids, esters, and water using near-infrared spectroscopy (NIR) and four different multivariate calibration methods were realized. The four multivariate calibration methods were Genetic Inverse Least Squares (GILS), Genetic Regression (GR), Principle Component Regression (PCR), and Partial Least Squares (PLS). Four different esterification reactions were investigated. These are methyl acetate, ethyl acetate, propyl acetate, and butyl acetate.The sample set contains 40 ternary mixtures of these esterification processes. Duplicate measurements were done for each sample and 80 NIR absorbance spectra that cover the range from 4000 to 10000 cm.1 were obtained. Of these 80 spectra, 50 were used as calibration set, 30 were reserved for the prediction purposes. Several calibration methods were built for each component of each esterification reactions. Standard error of calibration (SEC) and standard error of prediction (SEP) were calculated for each calibration model and comparison of these four multivariate calibration methods was done.