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Öğe A Calix[4]arene-tren modified electrode for determination of Lead ions in aqueous solution(ACG PUBLICATIONS, 2019) Koçer, Mustafa Barış; Erdoğan, Zehra Özden; Oğuz, Mehmet; Küçükkolbaşı, Semahat; Yılmaz, MustafaIn this study, a simple and sensitive electrochemical sensor based on Calix[4]arene-tren (Calix-tren) modified glassy carbon (GC) electrode was developed for the determination of Pb (II) ions. Electrochemical behavior of Calix-tren modified electrodes were investigated by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results indicate that Calix-tren modified GC electrode provides good electron transmission pathway than bare GC electrode. The amount of Pb (II) was determined by differential pulse anodic stripping voltammetric analysis as a sensitive detection technique. The experimental parameters such as pH, deposition time and deposition potential were optimized. The optimum pH value was selected as 7.0. The effect of deposition potential and deposition time on the peak current was tested and the optimum values were chosen as -1.2 V and 120 s, respectively. Under the optimal conditions, the working range of the developed sensor was determined as 0.48-2.31 mu M, limit of detection (LOD) was 0.11 mu M and the RSD obtained in the reproducibility study was 2.78 %. It was also found that the developed method could be used in the determination of Pb (II) ions in real samples with satisfactory results.Öğe Elektrokimyasal Putresin Sensörü İçin Nanomalzemelere Dayalı Elektrot Materyallerinin Geliştirilmesi(Selçuk Üniversitesi Fen Fakültesi, 2022) Altun, Ayşe Betül; Erdoğan, Zehra Özden; Akın, İlker; Küçükkolbaşı, SemahatPoliaminler insan ve hayvanlarda fizyolojik işlevlerin yerine getirilmesinde önemli rol alırlar. Hücresel gelişim, hücre farklılaşması, enzim faaliyetlerinin ve iyon kanallarının düzenlenmesi, DNA ve protein sentezi kontrolünde görevlidirler. Putresin vücutta ornitinin dekarboksilasyonuyla oluşan bir poliamindir. Mantarlar tarafından da sentezlendiği bilinen bu madde, diğer poliaminlerin (spermidin, spermin) ön maddesidir. Gıdalarda ise putresin iki nedenle önem arz etmektedir. Birincisi, biyojen amin miktarının kalite indikatörü olarak kabul edilir olması diğeri ise sağlığa etkili toksik etkilerinin bulunmasıdır. Bu çalışmada; TiO2, CoS, TiO2-CoS nanopartikülleri ile modifiye edilmiş elektrotlar hazırlandı ve elektrokimyasal olarak putresin tayininde kullanılabilirliği araştırıldı. Hazırlanan modifiye elektrotların yüzey morfolojileri ve elektrokimyasal davranışları taramalı elektron mikroskopu (SEM), dönüşümlü voltametri (CV) ve elektrokimyasal impedans spektroskopisi (EIS) yöntemleri ile incelendi. Modifiye elektrotların performans faktörleri diferansiyel puls voltametrisi (DPV) yöntemiyle belirlendi ve modifiye edilmemiş elektrodun performansı ile karşılaştırıldı. Hazırlanan TiO2-CoS modifiye camsı karbon elektrodun (GCE) doğrusal çalışma aralığı 0,32 ?M - 16,66 ?M, gözlenebilme sınırı (LOD) 0,09 ?M, alt tayin sınırı (LOQ) 0,27 ?M, tekrarlanabilirlik ve tekrar üretilebilirlikleri sırasıyla %4,7 ve %3,3 olarak tespit edildi. Tasarlanan elektrodun gıda numunelerinde putresin analizi için kullanılabilirliği araştırıldı.Öğe Gıdalarda tiramin tayini için sensör geliştirilmesi(Selçuk Üniversitesi Fen Bilimleri Enstitüsü, 2018) Erdoğan, Zehra Özden; Küçükkolbaşı, SemahatThe aim of this thesis was to prepare both non-enzymativ and enzymatic electrodes by using TiO2-Ag/PPy, pillar[5]arene and tyrosinase for tyramine detection which is used as an indicator of deterioration in food. For this, the glassy carbon electrodes surfaces was modified with TiO2-Ag/PPy and pillar[5]arene which dispersed in gelatin solution. Surface morphologies and electrochemical properties of the prepared electrodes were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), alternating voltammetry (CV) and electrochemical impedance spectroscopy (EIS). In addition, optimum working conditions and performance factors for the modified electrodes were also determined. For GCE/Jel/TiO2-Ag/PPy, GCE/Jel/P[5]A, GCE/Jel/TiO2-Ag/PPy/TYR ve GCE/Jel/P[5]A/TYR, the linear working ranges were 0,04-3,07 µM, 0,04-1,49 µM, 0,02-7,43 µM and 1,64-42,05 µ; limits of detection were 0,02 µM, 0,04 µM, 0,04 µM and 0,53 µM; sensitivities were 8,03 nA/µM, 7,61 nA/µM, 2,31 nA/µM and 14,08 nA/µM, respectively. The availability of prepared electrodes was investigated by detection of tyramine in food samplesÖğe A Novel Chitosan Nanoparticle-Schiff Base Modified Carbon Paste Electrode as a Sensor for the Determination of Pb(II) in Waste Water(ESG, 2013) Küçükkolbaşı, Semahat; Erdoğan, Zehra Özden; Barek, Jiri; Şahin, Mustafa; Koçak, NuriyeThis paper describes the preparation and electrochemical application of a modified carbon paste electrode with a new kind of chitosan nanoparticle-Schiff base for the determination of Pb(II) ions in waste water using differential pulse anodic stripping voltammetry (DPASV). Firstly a new kind of chitosan nanoparticle-Schiff base (CNSB) was synthesized by chitosan nanoparticle reaction with 2,4-dihydroxybenzaldehyde. CNSB structure was characterized by FT-IR spectroscopy, elemental analysis, particle size and zeta potential. Afterwards, a novel, simple and effective chemically modified carbon paste electrode with CNSB was prepared and characterized using scanning electronic microscopy (SEM-EDX) and anodic stripping voltammetry. The modified electrode showed only one oxidation peak in the anodic scan at -0.35 V (vs. Ag/AgCl) for the oxidation of Pb(II). The electrochemical properties and applications of the modified electrode, including the pH, supporting electrolyte, preconcentration time, reduction potential and time, and percentage of modifier were investigated. The best voltammetric response was observed for a paste composition of 73.7% (w/w) of graphite powder, 5.3% (w/w) of chitosan and 21% (w/w) of paraffin oil, with 0.2 mol L-1 NaAc solution at pH 6.0 as supporting electrolyte, preconcentration time of 600 s, a reduction potential of -0.1 V and reduction time of 10 s. The new electrode displays excellent response to Pb(II) which is linear in the range from 1x10(-6) to 1x10(-4) mol L-1, with a correlation coefficient of 0.998 and a detection limit of 7.24x10(-7) mol L-1.Öğe Synthesis and characterization of novel nano-chitosan Schiff base and use of lead (II) sensor(ELSEVIER SCIENCE BV, 2012) Koçak, Nuriye; Şahin, Mustafa; Küçükkolbaşı, Semahat; Erdoğan, Zehra ÖzdenA new kind of nano-chitosan Schiff base ligand (CHNS) with particle size of 34 nm was formed by the reaction between the 2-amino groups of glucosamine residue of nano-chitosan and a 2,5-dihydroxybenzaldehyde. The chemical structures of the nano-chitosan and nano-chitosan Schiff base were characterized by FT-IR spectra, particle sizer, zeta potential, and elemental analysis. A new, simple and effective chemically modified carbon paste electrode with CHNS was prepared and used as a lead (II) sensor. The prepared electrode was characterized using scanning electronic microscopy (SEM-EDX) and cyclic voltammetry (CV). The modified electrode showed only one oxidation peak in the anodic scan at -0.34 V (vs. Ag/AgCl) for the oxidation of lead (II). The dedection limit (LOD) was calculated as 1.36 x 10(-7) for a 10-min preconcentration time at pH 6.0. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.Öğe Ürik asit tayini için nanopartikül temelli biyosensörler hazırlanması(Selçuk Üniversitesi Fen Bilimleri Enstitüsü, 2013-07-08) Erdoğan, Zehra Özden; Küçükkolbaşı, SemahatÜrik asit, idrar ve kan gibi biyolojik sıvılarda azot içeren başlıca bileşiktir. Birçok hastalık ve psikolojik rahatsızlıkta erken teşhis için önemli göstergedir. Kanda anormal seviyelerdeki ürik asit gut, hiperüremi, diyabet ve böbrek hastalıkları gibi birçok hastalığın belirtisidir. Bundan dolayı, insan fizyolojik sıvılarında ürik asit seviyesinin tespiti, bu hastalıkların teşhisinde vazgeçilmezdir. Bu çalışmada ürik asit tayini için, magnetit ile modifiye edilmiş karbon pasta enzim elektrot hazırlandı. Bu amaçla ürikaz enzimi, çapraz bağlama yöntemiyle karbon pasta matrikse immobilize edildi. Hazırlanan enzim elektrot için optimum çalışma koşulları ve performans faktörleri incelendi. Enzim elektrot için optimum pH, enzim ve magnetit miktarı, tampon derişimi ve çalışma potansiyeli sırasıyla; 7,5, 0,75 U, 3mg, 0,10 M ve +0,500 V olarak bulundu. Optimum çalışma koşullarında enzim elektrot için çalışma aralığı 1-1000 µM ve gözlenebilme sınırı 0,77µM olarak belirlendi. Enzim elektrodun cevap süresi 50 s, raf ömrü 10 gün ve tekrarlanabilirliğinin hesaplanması sırasında ölçülen akım farkı değerlerinin bağıl standart sapması % 4,94?dur. Enzim elektrodun cevabına, biyolojik sıvılarda bulunan ve girişim etkisi yapan diğer türlerin etkisi incelendi. İmmobilze enzim için görünür Michaelis-Menten sabiti (Km) 5,202 µM olarak hesaplandı.Öğe The Use of Voltammetry for Sorption Studies of Pb2+ from Aqueous Media using Schiff Base Immobilized Biologic Polymer Material(SPRINGER INTERNATIONAL PUBLISHING AG, 2013) Küçükkolbaşı, Semahat; Erdoğan, Zehra Özden; Koçak, Nuriye; Şahin, Mustafa; Gübbük, İlkay HilalAdsorption by low-cost adsorbents and biosorbents is recognized as an effective and economic method for low-concentration heavy metal. The purpose of this study was to investigate the possibility of the utilization of N,N'-bis(2,5-dihydroxybenzylidene)-1, 4-diaminobenzene (DHDB)-immobilized sporopollenin (Schiff base-immobilized sporopollenin, Sp-DHDB) as a sorbent for removal of lead (II) ion from aqueous solution. The effects of different parameters (such as sorbate concentration, sorbent dosage, and pH of the medium) were investigated by differential pulse anodic stripping voltammetry (DPASV) technique. The experimental data were analyzed by the Freundlich, Langmuir, and Dubinin-Radushkevich (D-R) isotherms. Equilibrium data fitted well with the Freundlich model and the procedure developed was successfully applied for the removal of lead ions in aqueous solutions. This investigation reveals a new, simple, environmentally friendly, and cost-effective method for the removal of lead ions from aqueous solutions by a new Sp-DHDB material.
