Yazar "Cengiz, Mahmut Alper" seçeneğine göre listele

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    Development of Gum-Arabic-based polyurethane membrane-modified electrodes as voltammetric sensor for the detection of phenylalanine
    (Springer, 2021) Alisik, Funda; Burc, Muammer; Titretir Duran, Serap; Gungor, Oznur; Cengiz, Mahmut Alper; Koytepe, Suleyman
    In this study, L-phenylalanine (L-Phe) sensors were prepared from Gum-Arabic-based polyurethanes, by the modification of Pt electrode. Firstly, Gum-Arabic-based polyurethanes were synthesized by solution polymerization technique and characterized with Fourier transform infrared spectroscopy, thermogravimetric analysis, differential thermal analysis, scanning electron microscopy and atomic force microscopy techniques. Then, L-Phe selective electrodes were prepared by coating the platinum electrode with different thickness Gum-Arabic-based polyurethane. L-Phe responses of the modified electrodes were investigated by differential pulse voltammetry technique. Sensor parameters such as scanning speed, film thickness, electrolyte type and pH were examined in detailed. Prepared electrodes were showed R-2 = 0.9972 for the concentration range of 200-1000 mu M L-Phe. The limit of detection and the limit of quantification of the prepared L-Phe selective modified electrode were calculated as 48.01 mu M and as 144.02 mu M, respectively. After ten consecutive measurements with the prepared L-Phe selective electrode, 98.8% stable result was obtained between the first and tenth reading and the RSD% value was found to be 1.21% for ten replicates. Consequently, prepared Gum-Arabic-modified sensors can be used successfully for the detection of the L-Phe with large concentration areas, high sensitivity and repeatability. [GRAPHICS] .
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    Fructose-Based Polyurethane Membranes: Synthesis, Characterization, and Their Use as Voltammetric pH Electrode
    (Taylor & Francis As, 2015) Gungor, Oznur; Pasahan, Aziz; Cengiz, Mahmut Alper; Koytepe, Suleyman; Seckin, Turgay
    In this study, polyurethane films prepared from the 4,4-diphenylmethane diisocyanate (MDI), ethylene glycol, and different ratio fructose were used to prepare a novel amperometric pH electrode. Fructose-based films were characterized by FT-IR, DSC, DTA, and TGA. Prepared polyurethanes exhibited suitable T-g(degrees C), good thermal stability and good adhesive properties. The incorporation of saccharides into the PU structure results in a higher crosslinking density and a higher content of hard segments. Furthermore, the behavior of films prepared from polyurethane solutions containing 1%, 3%, 5%, and 10% fructose toward pH changes were examined by normal pulse voltammograms technique and diferantial pulse voltammetry. [GRAPHICS] .
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    Synthesis and characterization of polyurethanes containing glucose for selective determination of epinephrine in the presence of a high concentration of ascorbic acid
    (Wiley-Blackwell, 2013) Pasahan, Aziz; Koytepe, Suleyman; Cengiz, Mahmut Alper; Seckin, Turgay
    Polyurethane (PU) films were prepared from glucose, ethylene glycol and diphenylmethane diisocyanate and used to construct a novel polymer electrode for the detection of epinephrine (EP) in the presence of a high concentration of ascorbic acid (AA). The NCO:OH molar ratio was kept constant at 1 and the saccharide content was varied. The PUs were characterized using Fourier transform infrared spectroscopy, differential scanning calorimetry and differential thermal and thermogravimetric analyses, with intrinsic viscosity and adhesive properties also being evaluated. The PUs exhibited high glass transition temperature, good thermal stability and good adhesive properties. The incorporation of saccharides into the PU structure resulted in a higher crosslinking density and a higher content of hard segments. Medium- to high-molecular-weight polymers were obtained, with inherent viscosities near or higher than 0.982.14 dL g-1. The solubility of the PUs was much better than that of aromatic PUs. The modified polymer electrodes were then used to determine EP in the presence of a high concentration of AA using differential pulse voltammetry. From the amperometric results for the PU electrode, it is concluded that a PU film containing 5 wt% glucose can be used as a membrane for EP detection in the presence of a large concentration of AA, because of its strong adherence to the electrode surface, easy preparation, chemical stability, selectivity and very high statistical confidence (R = 0.9994). (C) 2012 Society of Chemical Industry
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    Synthesis, Characterization of Guar-Containing Polyurethane Films and their Non-enzymatic Caffeic Acid Sensor Applications
    (Taylor & Francis Inc, 2017) Duran, Serap Titretir; Pasahan, Aziz; Ayhan, Nurcan; Gungor, Oznur; Cengiz, Mahmut Alper; Koytepe, Suleyman
    Stable voltammetric sensors were fabricated by dropping the guar-containing polyurethane films on a platinum electrode for the non-enzymatic determination of caffeic acid. The voltammetric responses of PU-G-1% toward caffeic acid have a linear concentration range from 1 to 15mM with a correlation coefficient of 0.9938. The detection limit of PU-G-1% electrode was approximately 0.25mM. PU-G-1% sensor showed the good sensitivity, selectivity, high R-value, low detection limit, and high reproducibility toward caffeic acid. Therefore, it is claimed that the polyurethane film containing 1% guar can be used as an excellent selective membrane for caffeic acid detection in the presence of interferent molecules. [GRAPHICS] .