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Öğe Development of gallic acid sensors based on polyimide-modified platinum electrode(Taylor & Francis Inc, 2019) Pasahan, Aziz; Ayhan, Nurcan; Ozcan, Imren; Duran, Serap Titretir; Koytepe, SuleymanA series aromatic polyimide (PI) membranes in the form of permselective films was synthesised from different dianhydrides with two diamine monomers for gallic acid (GA) measurement. The obtained PI films were examined by Spectroscopic techniques, Scanning Electron Microscopy (SEM) and thermal analysis techniques and then used to fabricate the selective films on the modified electrode. Because of their excellent film properties, as the permselective polymeric membranes were used for determination of GA in the presence of various interferences and real sample. The PI-1-modified Pt electrode showed a very high R-value (0.9935) and reproducibility for GA determination, as well as high selectivity. [GRAPHICS]Öğe Development of voltammetric sensor based on polyimide-MWCNT composite membrane for rapid and highly sensitive detection of paracetamol(Elsevier Sci Ltd, 2020) Burc, Muammer; Koytepe, Suleyman; Duran, Serap Titretir; Ayhan, Nurcan; Aksoy, Busra; Seckin, TurgayIn this work, for low level detection of paracetamol (PA) a voltammetric sensor was obtained. Polyimidemultiwall carbon nanotube (PI-MWCNT) composite film was used for modification of platinum (Pt) electrode as selective membrane. Firstly, this PI-MWCNT film was synthesized with 2,5-diaminopyridine (DAP), 4,4'-oxydiphthalic anhydride (ODPA) and MWCNT as a reinforcement by thermal imidization technique. The morphology, micro and chemical structures of the obtained composite film were studied by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and thermal analysis techniques. Then, the paracetamol sensor was prepared via the modification of Pt electrode with prepared PI-MWCNT composite film. Pt electrode was modified by coating with prepared PI-MWCNT composite film. Modified Pt electrode was used as PA sensor due to its selective membrane property in the presence of interfering substances for the electrochemical detection of PA. Electrochemical behaviour of paracetamol at the polyimide film modified Pt electrode was obtained by differential pulse voltammetry (DPV) and cyclic voltammetry (CV) method. It has shown that the modified electrode exhibits remarkable repeatability and precision in analytical paracetamol response as compared with other modified paracetamol electrodes. Comparing the responses of modified electrode with the unmodified Pt electrode, selectivity, sensitivity and stable responses significantly enhanced. A linear calibration plot having a correlation coefficient of 0.997 was obtained in the concentration range from 0.3 to 1.8 mM paracetamol. A linear calibration plot for low concentration area having a correlation coefficient of 0.999 was obtained in the concentration range from 0.002 to 0.05 mM paracetamol. Detection limit (LOD) and quantitative limit (LOQ) for paracetamol detection of PI-MWCNT modified electrode were calculated as 0.002 mM and 0.006 mM respectively. In addition, the presented method was applied for determination of PA in commercial tablets. The recovery efficiency of the PI modified electrode was obtained range of 96% and 102% for three different tablets. As a result; a simple, rapid, low cost, repeatable method showing good accuracy and precision (99.4%) has been developed for the selective and sensitive determination of paracetamol by prepared PI-MWCNT composite film modified electrode. (C) 2019 Elsevier Ltd. All rights reserved.Öğe Polifenol türevli antioksidanlar için sensör geliştirilmesi ve analitik uygulamaları(İnönü Üniversitesi, 2018) Ayhan, NurcanBu çalışmada amaç; gallik asit, kafeik asit ve kateşin gibi polifenol türevli antioksidanların yan yana ve/veya bu antioksidanlardan birine veya birkaçına karşı seçicilik gösterebilen polimer kaplı film elektrotlar geliştirmektir. Bu amaçla öncelikle poliimit ve poliüretan temelli polimerlerin karakterizasyonları FTIR, SEM, DSC, TGA ve DTA ile gerçekleştirilmiş ve sıvı temas açıları ölçülmüştür. Ardından poliimit ve poliüretanların n-metilpirolidon (NBS) içindeki çözeltisinden platin elektrot üzerine damlatılarak polimer film elektrotlar hazırlanmıştır. Hazırlanan polimer elektrotların amperometrik sensör karakteristikleri üzerine askorbik asit, kumarik asit gibi elektroaktif ve sükroz, maltoz, früktoz ve glukoz gibi elektroaktif olmayan interferansları engellemek için polimer türü, kurutma süresi ve polimer film kalınlığı gibi parametreler optimize edilmiştir. Daha sonra hazırlanmış olan gallik asit, kafeik asit ve kateşin sensörlerinin interferanslar yanında seçicilik, kararlılık ve duyarlığı değerlendirilmiştir. Sonuç olarak; her biri için ayrı ayrı hazırlanmış olan polimer kaplı elektrotların interferantları engellerken; gallik asit, kafeik asit ve kateşine düzenli DPV yanıtları verdiği bulunmuştur. Gallik asit, kafeik asit ve kateşin için sırasıyla regrasyon katsayısı (R2) 0.9935, 0.9938, 09933; tayin sınırı (LOD), 0.027, 0.507 0.023 ve kantitasyon sınırı (LOQ) değerleri, 0.081, 1.522, 0.069 olarak hesaplanmıştır. Gallik asit, kafeik asit ve kateşin için elektrokimyasal sensörler başarıyla geliştirilmiştir.Öğe Preparation of triaminotriazine-based polyimide-modified electrodes and their use for selective detection of catechin in green tea samples(Springer, 2020) Duran, Serap Titretir; Ayhan, Nurcan; Aksoy, Busra; Koytepe, Suleyman; Pasahan, AzizAn effective electrochemical sensor was developed from triaminotriazine-based polyimide (PI) films as selective membrane for the detection of catechin (CT). Firstly, triaminotriazine-based PI films were synthesized from 2,4,6-triamino-1,3,5-triazine (TAT) and pyromellitic dianhydride by thermal imidization method with different monomer ratios. Structural and morphological of synthesized PI films were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. Prepared polyimide films were used as membrane for the preparation of the modified electrodes. Catechin (CT) selectivity behavior of polyimide-modified Pt electrodes was investigated by means of differential pulse voltammetry (DPV). DPV voltammograms showed that peak currents of the modified electrode increased proportionally with increase in CT concentration. TAT-PI-1/1 sensor showed high selectivity, a high regression coefficient (R value = 0.9982 ), good repeatability (RSD of 2.15%), and limit of detection 0.0152 mM for catechin determination in the presence of multiple interferent species (1 mM coumaric acid, ascorbic acid, gallic acid, lactose, sucrose, fructose, maltose and glucose). Moreover, the TAT-PI-1/1 sensor was employed to determine CT in real sample.Öğe 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, SuleymanStable 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] .
