Browsing by Author "Koçak S."
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Item Simultaneous Differential Pulse Polarographic Determination of Cadmium, Lead, and Copper in Milk and Dairy Products(2004) Tokuşoǧlu Ö.; Aycan Ş.; Akalin S.; Koçak S.; Ersoy N.The contents of potentially toxic elements lead and cadmium and the essential element copper in various milk and dairy products consumed in Turkey were determined by differential pulse polarography (DPP), primarily to assess whether the intakes comply with recommended desired concentrations for essential and permissible levels for toxic elements. A simple and rapid DPP method has been developed for the simultaneous determination of cadmium, lead, and copper in samples. Using the differential pulse mode, half-wave peak potentials as E1/2 were -0.58, -0.40, and -0.07 V for cadmium (Cd), lead (Pb), and copper (Cu), respectively. Marketed formulations of dairy products have been analyzed by calibration and standard addition methods. Recovery experiments were found to be quantitative. The linear domain ranges were 0.00-674.28 μg/L for Cd (R2 = 0.9999), 0.19-2.94 mg/L (p < 0.01) for Pb (R2 = 0.9997), and 0.41-133.46 μg/L for Cu (p < 0.01) (R2 = 0.9999). The studies have shown that the method is a rapid, reproducible, and accurate determination of these elements in milk and dairy products and can be used in the analysis of marketed formulations in the milk and dairy industry.Item The contents of sesamol and related lignans in sesame, tahina and halva as determined by a newly developed polarographic and stripping voltametric analysis(2009) Tokusoglu O.; Koçak S.; Aycan S.The contents of antioxidant lignans (Sesamol) in sesame, commercial formulations of tahina and halva, which are processed tahina foods, were determined by Differential Pulse Polarography (DPP) with a capillary hanging mercury drop electrode (HMDE). A platinum wire was used as the counter electrode and Ag/AgCl was the reference electrode. Samples have been analyzed by standard addition procedures and found to be quantitative (p<0.01). Due to the fact that sesamo is an oil-soluble phenolic compound , it was found in the oil levels of sesame, tahina and halvas. Sesame samples contained 51.05-56.46 % in oil whereas tahina samples contained 52.12-53.79 % in oil. The oil percentage of plain halva was found to be 28.79 - 30.13 % (p<0.01). Phenolic lignan sesamol in sesame was 0.26-0.32 mg/100g oil, whereas the sesamol in tahina was 10.98-12.33 mg/100g oil. The sesamol in commercial plain halva samples and the open marketed plain halva samples contained 8.24-9.12 mg/100g oil and 4.97 mg sesamol /100g oil, respectively (R2=0.9999) (p<0.01). The proposed Differential Pulse Polarographic (DPP) method is a rapid, reproducible procedure for the simultaneous determination of phenolic lignans in sesame and food products with sesame. It provides an adequate, sensitive, quantitative detection of these nutraceuticals in the commercial food industry.Item Electrocatalytic oxidation of methanol at Pd and Pt ad-layer modified Au(111) electrodes in alkaline solution(2011) Koçak S.; Dursun Z.; Ertaş F.N.The electrochemical oxidation of methanol was investigated by using various ad-layer modified Au(111) electrodes in alkaline media in comparison to Au(111), polycrystalline Pd, and polycrystalline Pt electrodes. Catalytic activity of gold toward methanol oxidation has tended to increase in more alkaline media, as reflected in the oxidation peak in the concentration range of NaOH (0.1-3.0 M) studied here. The oxidation peak potential of methanol shifted to more negative potentials, indicating a pH-dependent surface reaction. Among the electrodes studied, single-crystal gold electrode surfaces modified with Pd and Pt ad-layers displayed the highest catalytic activity for methanol oxidation. Additional shifts of about 350 mV in the oxidation peak potential of methanol was observed for both ad-layer modified electrodes to more negative potentials compared to that of bare electrodes. The Pd and Pt ad-layer modified Au(111) electrode surfaces did not only supply a superior electrical contact, but also accelerated electron transfer, as shown by the increase in peak current and the positive shift in peak potential. This effect was supported by the doublelayer capacitance measurements of bare Au(111) and Pd ad-layer modified singlecrystal electrodes where the potential of zero charge changed from 15 to 5 mV.Item A spectrophotometric method for determination of molybdenum in water samples by using pyrogallol red and a water soluble ionic liquid(2013) Pelit L.; Koçak S.; Pelit F.O.; Türkmen H.; Ertaş F.N.The present study describes a simple and sensitive spectrophotometric method for the determination of molybdenum in real water samples. The method is based on the hyperchromic and bathochromic effect of an ionic liquid namely, 1-methyl-3-octadecyl-imidazolium bromide (C18mimBr), on molybdenum ion (Mo(vi)) and pyrogallol red (PGR) complex. The ternary complex of Mo-PGR-C18mimBr displays a distinct absorption peak with excellent analytical characteristics and offers the advantages of simplicity for the determination of Mo(vi) ions, without any need for a solvent extraction step. The limit of detection (LOD) and limit of quantification (LOQ) of the method were calculated as 0.74 ng mL-1 and 2.47 ng mL-1 respectively. The method was validated and applied successfully to the determination of Mo(vi) ions in real water samples. The interference of ferric ions was shown to be removed from samples with less ionic content by using an ion exchange resin prior to the analysis, and the performance of the method was compared with that of ICP-MS. © 2013 The Royal Society of Chemistry.Item Electrochemical deposition and behavior of mixed-valent molybdenum oxide film at glassy carbon and ITO electrodes(Elsevier B.V., 2013) Koçak S.; Ertaş F.N.; Dursun Z.The effect of solution composition and the type of the anionic species on the electrochemical formation of mixed-valent molybdenum oxide on a glassy carbon and ITO electrode surfaces was elucidated. Susccessive recording of the voltammograms has shown that anionic species display different stabilizing effect on the reductive formation of hydrogen molybdenum bronzes [MoO 3-x (OH) x ] and chloroacetic acid buffer has given the best results. The deposit was built upon cycling the potential between 0 and -0.9 V (vs. Ag/AgCl) via reduction of Mo(VI) to Mo(V) on the electrode surface in pH 3.0 chloroacetic acid solution. Electrochemical impedance measurements carried out in this medium revealed a shift in potential zero charge values from -0.2 V to -0.55 V after the potential of the GCE had been cycled for 30 min. An establishment of mixed-valent molybdenum oxide deposit by time on the gold electrode surface was proved by quartz crystal microbalance measurements. Atomic force and scanning electron microscopy techniques were made use of so as to characterize the surface structures of the electrodes. X-ray photoelectron spectroscopy studies confirmed that the deposit contains both Mo(V) and Mo(VI). The deposited films exhibited unique catalytic activity towards nitrite oxidation consistent with the change in peak characteristics. © 2012 Elsevier B.V. All rights reserved.Item Molybdenum oxide/platinum modified glassy carbon electrode: A novel electrocatalytic platform for the monitoring of electrochemical reduction of oxygen and its biosensing applications(2013) Çakar I.; Özdokur K.V.; Demir B.; Yavuz E.; Demirkol D.O.; Koçak S.; Timur S.; Ertaş F.N.The reduction of oxygen to water is one of the most important reactions in electrochemistry with regards to the wide range of applications in electrocatalysis, metal corrosion, and fuel cell and mostly in biosensor studies. Present study describes the use of a glassy carbon electrode modified with platinum and molybdenum oxide (Pt-MoOx) in strongly acidic solutions for electrocatalytic reduction of oxygen dissolved in buffer solution for the first time. The dispersion of Pt nanoparticles on MoOx provides larger surface area and better electrocatalytic activity for oxygen reduction and the best response toward dissolved oxygen was obtained with a mole ratio of 1:90 Pt:Mo in deposition solution. The modified surface was then used as a biosensing platform for the monitoring of oxygen consumption due to the bio-catalytic action of glucose oxidase (GOx) as the model enzyme. After optimization of the operational conditions, analytical characterization and application of the glucose oxidase GOx biosensor to flow injection analysis mode have been successfully performed. © 2013 Published by Elsevier B.V. All rights reserved.Item Centri-voltammetric determination of molybdenum(Royal Society of Chemistry, 2013) Koçak S.; Ertaş F.N.Centri-voltammetry is a method developed in the last decade which combines the advantages of centrifugation and voltammetry and hence provides a practical way for application of co-precipitation in trace analysis allowing direct voltammetric scan. The present study describes another application of the centri-voltammetric method for the determination of biologically essential trace elements, in particular, molybdenum ion. For this purpose, a dual-functional voltammetric cell adjustable to the centrifuge was designed and utilized in the determination of molybdenum ions with various carrier reagents, i.e. oxine, pyrogallol red, and cupferron. Optimization studies include solution properties as well as voltammetric measurement and centrifugal parameters. Among the reagents studied, the best results were obtained with pyrogallol red and the reduction peak current of the complex was utilized for analytical purposes. The limit of detection from calibration curves was calculated to be 9.4 × 10-9 M and a better sensitivity was obtained in the presence of chlorate ions that are known to have a catalytic effect on the reaction. The method was employed in the determination of molybdenum in milk samples and the results were compared with those obtained by the ICP-MS method. © The Royal Society of Chemistry 2013.Item Hydrazine oxidation at gold nanoparticles and poly(bromocresol purple) carbon nanotube modified glassy carbon electrode(Elsevier, 2014) Koçak S.; Aslişen B.Bromocresol purple monomers were polymerized electrochemically at carbon nanotube modified glassy carbon electrode surface and obtained electrodes were donated as poly(BCP)/CNT/GCE. After electrochemical polymerization, Au nanoparticles were doped on the polymer film carbon nanotube modified glassy carbon electrode surface by electrochemical reduction from their acidic solutions. Modified electrodes are characterized with electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) techniques. The electrochemical behavior of hydrazine oxidation was investigated at gold nanoparticles modified poly(BCP)/CNT electrodes in pH 10.0 phosphate buffer solution. The obtained results were compared with other modified electrodes. The best catalytic activity was obtained at AuNPs/poly(BCP)/CNT/GCE due to the shift of oxidation peak to more negative values than other electrodes with a higher current value. The peak potential and current oxidation of hydrazine were obtained at AuNPs/poly(BCP)/CNT/GCE (-28 mV, 205 μA) and poly(BCP)/CNT/GCE (427 mV, 80 μA). Under optimal conditions, the calibration curves for hydrazine were obtained over the range of 5.0 × 10-7-1.0 × 10-3 M. The limit of detection for hydrazine was calculated as 1.0 × 10-7 M for AuNPs/poly(BCP)/CNT/GCE. © 2014 Elsevier B.V.Item Polymer Film Supported Bimetallic Au–Ag Catalysts for Electrocatalytic Oxidation of Ammonia Borane in Alkaline Media(SpringerOpen, 2016) Karabiberoğlu Ş.U.; Koçak Ç.C.; Koçak S.; Dursun Z.Abstract: Ammonia borane is widely used in most areas including fuel cell applications. The present paper describes electrochemical behavior of ammonia borane in alkaline media on the poly(p-aminophenol) film modified with Au and Ag bimetallic nanoparticles. The glassy carbon electrode was firstly covered with polymeric film electrochemically and then, Au, Ag, and Au–Ag nanoparticles were deposited on the polymeric film, respectively. The surface morphology and chemical composition of these electrodes were examined by scanning electron microscopy, transmission electron microscopy, electrochemical impedance spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. It was found that alloyed Au–Ag bimetallic nanoparticles are formed. Electrochemical measurements indicate that the developed electrode modified by Au–Ag bimetallic nanoparticles exhibit the highest electrocatalytic activity for ammonia borane oxidation in alkaline media. The rotating disk electrode voltammetry demonstrates that the developed electrode can catalyze almost six-electron oxidation pathway of ammonia borane. Our results may be attractive for anode materials of ammonia borane fuel cells under alkaline conditions. Graphical Abstract: [Figure not available: see fulltext.] © 2016, The Author(s).Item Determination of oleuropein using multiwalled carbon nanotube modified glassy carbon electrode by adsorptive stripping square wave voltammetry(Elsevier B.V., 2016) Cittan M.; Koçak S.; Çelik A.; Dost K.A multi-walled carbon nanotube modified glassy carbon electrode was used to prepare an electrochemical sensing platform for the determination of oleuropein. Results showed that, the accumulation of oleuropein on the prepared electrode takes place with the adsorption process. Electrochemical behavior of oleuropein was studied by using cyclic voltammetry. Compared to the bare GCE, the oxidation peak current of oleuropein increased about 340 times at MWCNT/GCE. Voltammetric determination of oleuropein on the surface of prepared electrode was studied using square wave voltammetry where the oxidation peak current of oleuropein was measured as an analytical signal. A calibration curve of oleuropein was performed between 0.01 and 0.70 μM and a good linearity was obtained with a correlation coefficient of 0.9984. Detection and quantification limits of the method were obtained as 2.73 and 9.09 nM, respectively. In addition, intra-day and inter-day precision studies indicated that the voltammetric method was sufficiently repeatable. Finally, the proposed electrochemical sensor was successfully applied to the determination of oleuropein in an olive leaf extract. Microwave-assisted extraction of oleuropein had good recovery values between 92% and 98%. The results obtained with the proposed electrochemical sensor were compared with liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. © 2016 Elsevier B.V.Item Development of pulsed deposited manganese and molybdenum oxide surfaces decorated with platinum nanoparticles and their catalytic application for formaldehyde oxidation(Elsevier Ltd, 2016) Özdokur K.V.; Tatli A.Y.; Yilmaz B.; Koçak S.; Ertaş F.N.Manganese and molybdenum mixed oxides were co-deposited in a thin film form by pulsed deposition technique on a glassy carbon substrate, and this mixed oxide film was further decorated with platinum nanoparticles. Formaldehyde, being a candidate for proton exchange membrane fuel cell applications, was chosen as the test material for the catalytic activities of the developed surface in alkaline media. The synergetic effect of the mixed metal oxide deposit incorporating Pt nanoparticles was verified by using different mol ratios of the corresponding metal ions and applying pulsed deposition conditions and under optimized conditions and, resultant oxidation peak has shown a significant increase in the peak current accompanied by the small shift in the peak potential. The modified composite electrodes were characterized by SEM, EDX, XPS and EIS. © 2016 Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.Item Electrochemical Determination of Hydrazine at Gold and Platinum Nanoparticles Modified Poly(L-Serine) Glassy Carbon Electrodes(Taylor and Francis Inc., 2016) Koçak S.; Altın A.; Koçak Ç.C.ABSTRACT: L-serine monomer was polymerized electrochemically on a glassy carbon electrode by cyclic voltammetry. After L-serine polymerization, gold and platinum metal nanoparticles were doped by electrochemical reduction on the surface. The modified electrodes were characterized by using scanning electron microscopy and electrochemical impedance spectroscopy. The electrochemical behavior of hydrazine oxidation at the electrodes was investigated in 0.1 M pH 7.0 phosphate buffer. Hydrazine oxidation peaks were observed at 650, 399, 280, and −395 mV at the bare glassy carbon, poly(L-serine) modified glassy carbon, gold nanoparticle modified poly(L-serine) film glassy carbon electrode, and platinum nanoparticles modified poly(L-serine) film glassy carbon electrode, respectively. The most active surface towards hydrazine oxidation was the platinum nanoparticle modified poly(L-serine) film glassy carbon electrode with a 1045 mV negative potential shift and approximately three-fold higher peak current. The hydrazine oxidation peak was shifted to a 370 mV negative potential with a 2.5 times higher current at the gold nanoparticle modified poly(L-serine) film glassy carbon electrode compared to the bare electrode. The linear concentration ranges were from 1.0 to 1000 µM and 0.5 to 1000 µM for the gold nanoparticle modified poly(L-serine) film glassy carbon and the platinum nanoparticles modified poly(L-serine) film glassy carbon electrodes with limits of detections of 0.5 and 0.2 µM, respectively. © 2016, Copyright © Taylor & Francis Group, LLC.Item Determination of Hydrazine at a Platinum Nanoparticle and Poly(Bromocresol Purple) Modified Carbon Nanotube Electrode(Taylor and Francis Inc., 2016) Koçak S.; Aslışen B.; Koçak Ç.C.ABSTRACT: Bromocresol purple was polymerized electrochemically at a carbon nanotube modified glassy carbon electrode and platinum nanoparticles were doped on the polymer film by electrochemical reduction. The modified electrodes were characterized by electrochemical impedance spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The oxidation of hydrazine was investigated at the platinum nanoparticle modified electrode in phosphate buffer. The results were compared with those obtained using other modified and bare electrodes. The best catalytic activity was obtained at the platinum nanoparticle modified electrode due to shift of the oxidation peak to more negative values and highest current. The peak potential and current for hydrazine were −445 mV and 175.5 µA, respectively. Linear calibration curves for hydrazine were obtained from 10 to 1000 mM. The limits of detection and quantitation for hydrazine were 1.0 and 3.0 mM, respectively. © 2016, Copyright © Taylor & Francis Group, LLC.Item Electrochemical Preparation and Characterization of Gold and Platinum Nanoparticles Modified Poly(taurine) Film Electrode and Its Application to Hydrazine Determination(Elsevier B.V., 2016) Koçak Ç.C.; Altın A.; Aslışen B.; Koçak S.A highly sensitive hydrazine sensor has been developed by using gold and platinum nanoparticles (NPs) decorated poly(taurine) on modified glassy carbon electrode (GCE). First, poly(taurine) modified glassy carbon electrode was prepared by electropolymerization method using cyclic voltammetry. Then, a thin layer of poly(taurine) is coated electrochemically on a GCE and the effective parameters have been optimized. After taurine polymerization, metal nanoparticles (Au and Pt) were doped by electrochemical reduction from metal ions solution on poly(taurine)/GCE surface. Modified electrodes were characterized by using different surface techniques. The obtaining results were compared with bare GCE, poly(taurine) modified glassy carbon electrode, AuNPs/poly(taurine)/GCE, and PtNPs/poly(taurine)/GCE. The peak potential of hydrazine oxidation on bare GCE, poly(taurine)/GCE, AuNPs/poly(taurine)/GCE, and PtNPs/poly(taurine)/GCE were observed at 690 mV, 401 mV, 341 mV, and -370 mV, respectively. Finally, these modified electrodes were successfully used for the oxidation of hydrazine and exhibited excellent electrocatalytic activity with respect to hydrazine oxidation. The better sensitivity and selectivity exhibited the amperometric techniques to compare other techniques. The linear concentration ranges were found between 0.1 to 1000 μM (R2 = 0.9981) for AuNPs/poly(taurine)/GCE. The limit of detection (LOD) and limit of quantitation (LOQ) values were calculated to be 0.05 μM and 0.15 μM, respectively. The practical application of the sensor was evaluated in river water samples with good recoveries. © 2016 The Authors. Published by ESGItem Lead and copper removal using Kula volcanics from environmental waters(Taylor and Francis Inc., 2017) Yayayürük O.; Erdem Yayayürük A.; Koçak Ç.; Koçak S.The ability of Kula volcanics (the youngest volcanic rocks of western Anatolia) to remove Pb(II) and Cu(II) from aqueous solutions has been demonstrated, for the first time, in this study. The optimum parameters viz., pH, contact time and sorbent amount/solution volume ratio were evaluated using batch experiments. Langmuir isotherm model excellently described the sorption process and both of the ions followed pseudo-second-order kinetics. The method was applied to the natural river water samples and it was observed that the sorbent can successfully be used for the removal Pb(II) and Cu(II) ions with acceptable accuracy and precision. © 2017 Taylor & Francis.Item Nanostructured Metal–Metal Oxides and Their Electrocatalytic Applications(wiley, 2018) Özdokur K.V.; Koçak S.; Ertaş F.N.Electrochemical nanotechnologies have witnessed great fundamental advances in the last two decades. The strong interaction between the nanoscience and electrochemistry has led intensified studies on nanostructured materials for electronic, electrochromic, catalytic, and analytical applications. Many researchers have focused on metallic and carbon-based nanomaterials for electrocatalysis, energy conversion systems, and sensor development. The requirement of improvement of the performance of conventional Pt-based catalysts along with the search for low cost alternatives has led to the development of multicomponent catalysis systems. Due to their abundant sources and low cost, transition metal oxides offer a wide range of applications in various fields. However, their performance was found to be dependent on the synthesis procedure. Electrochemical deposition is usually the method of choice not only because this technique is a more practical and economical way for readily producing large uniform oxide thin films but also because the technique provides the controlling of the nature of the deposit by changing the deposition parameters. By this means, a mixed-valent metal oxide (MeOx) film can be produced on a carbon or other substrates, which is believed to be responsible for their catalytic activities. Further improvement in the catalytic performance can be maintained by the combination of hyper-d electronic noble metals, platinum in particular, with hypo-d electronic transition metal oxides. This chapter also covers the recently developed deposition techiques such as electrochemical pulsed deposition (PD). This technique favors the formation of nucleation sites and hence contributes to a high dispersion of the deposits compared to other methods. The performance of the electrode on both anodic and cathodic directions can be further enhanced by decorating with metallic nanoparticles and carbon nanotubes. © 2019 Scrivener Publishing LLC.Item Sorption of uranium(VI) from aqueous solutions by DEEA organo-volcanic: isotherms, kinetic and thermodynamic studies(Springer Singapore, 2018) Kaynar Ü.H.; Hiçsönmez Ü.; Çam Kaynar S.; Koçak S.The sorption of the uranium(VI) ions from aqueous solutions by diethylethanolammonium organo-volcanics (Kula-TURKEY) was investigated under different experimental conditions. DEEA was used to modify the surface of basaltic volcanics. The characteristic of basaltic volcanic was analyzed by XRF, SEM–EDS, FTIR, and XRD. The BET surface areas of unmodified volcanics and DEEA-modified volcanics were found as 2.265 and 3.689 m2/g, respectively. The volcanic samples were treated by using different concentrations of DEEA. The adsorption of U(VI) on natural and modified volcanics was examined as a function of the contact time, initial pH of the solution, initial U(VI) concentration, and temperature. Langmuir, Freundlich, and D–R adsorption isotherms were used to describe the adsorption. While examining the adsorption percentage and distribution coefficient, these values for unmodified volcanics were found to be 25% ± 0.76 and 10.08 mL/g, while the values for the DEEA-modified volcanics were 88% ± 1.04 and 220 mL/g, respectively. The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data. In this study, it can be seen that the adsorption process is suitable for the pseudo-second-order kinetic model. Various thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were calculated with the thermodynamic distribution coefficients obtained at different temperatures. The sorption process was a chemical adsorption process. The results indicated that the processes are spontaneous and endothermic. © 2018, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Chinese Nuclear Society, Science Press China and Springer Nature Singapore Pte Ltd.Item Highly improved electrocatalytic oxidation of dimethylamine borane on silver nanoparticles modified polymer composite electrode(TUBITAK, 2020) Koçak Ç.C.; Koçak S.; Karabi̇Beroğlu Ş.; Dursun Z.Dimethylamine borane (DMAB) is a promising fuel alternative for fuel cell applications. In this work cyclic voltammetric behavior of DMAB was investigated on the polymerized aminophenol film decorated with Ag nanoparticles in alkaline media. The polymer film was formed on the glassy carbon electrode by electrochemical technique and then, the surface was modified with Ag nanoparticles. The surface of the modified electrode was identified by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy techniques. The developed electrode has displayed high electrocatalytic activity for DMAB oxidation in alkaline media depending on the supporting electrolyte concentration. Experimental parameters such as cycle number used in electropolymerization of p-aminophenol, deposition of Ag nanoparticles and supporting electrolyte were optimized. © TÜBİTAK.Item Enhanced Electrochemical Determination of Catechol and Hydroquinone Based on Pd Nanoparticles/Poly(Taurine) Modified Glassy Carbon Electrode(Wiley-VCH Verlag, 2020) Koçak Ç.C.; Koçak S.Here, Pd nanoparticles and poly(taurine) film was prepared on the glassy carbon electrode surface (Pd/Poly(TAU)/GCE) by the rapid electrochemical technique. The proposed composite surface was characterized by scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS) and electrochemical impedance spectroscopy(EIS). Enhanced electron transfer ability and higher electroactive surface area were achieved at Pd/Poly(TAU)/GCE as compared to the bare GCE and polymer film electrode. The new and highly stable Pd/Poly(TAU)/GCE was employed for the individual and simultaneous determination of hydroquinone and catechol which were environmentally toxic. Under the optimized conditions, HQ and CC were individually determined by using the differantial pulse voltammetry in the linear ranges of 0.008–100 μM and 0.001–100 μM with the detection limits of (LOD) 2.1 nM and 0.68 nM, respectively. In case of simultaneous determination, LODs were found as 10 nM and 0.88 nM for HQ and CC, respectively. The content of both analytes in the real sample analysis was evaluated in the river water and tap water successfully. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, WeinheimItem Electrochemical Determination of Sesamol in Foods by Square Wave Voltammetry at a Boron-Doped Diamond Electrode(Taylor and Francis Inc., 2020) Aslışen B.; Koçak Ç.C.; Koçak S.Sesamol is a phenolic compound naturally found in sesame seeds. It has beneficial health effects in humans, as it features significant antioxidant activity and has anticancer and anti-aging properties. Therefore, finding a suitable electrode surface for sesamol determination is important. The prominent advantage of boron-doped diamond electrodes is their use in many sensing platforms without the need for the surface modification. This study represents the first time that sesamol has been determined using boron-doped diamond electrodes in acidic media by square wave voltammetry. Linear responses of sesamol were obtained in the concentration range from 0.2 µM to 1000 µM, and the detection limit was determined to be 85 nM based on a signal-to-noise ratio of 3. The relative standard deviations were 2.1% for a 1 µM standard with three measurements. © 2019, © 2019 Taylor & Francis Group, LLC.