Browsing by Author "Kocak, S"

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    UPTAKE CHARACTERISTICS OF Pb(II), Cu(II) AND Zn(II) BY NATURAL MAGNETITE: APPLICATION TO RIVER SAMPLES
    Yayayuruk, AE; Yayayuruk, O; Kocak, CC; Kocak, S
    Natural magnetite was investigated for the removal of Pb(II), Cu(H) and Zn(H) ions from water samples. The optimum experimental conditions including pH, sorbent amount and contact time have been established. Langmuir isotherm model was found to be more suitable to represent the experimental equilibrium than Freundlich isotherm model. The experimental kinetic data were a better fit with pseudo-second order reactions rather than pseudo-first order equation. The sorbent selectively removed Pb(II), Cu(H) and Zn(H) ions in the presence of several competitor ions (>= 98%). The application of the sorbent for the removal of Pb(H), Cu(H) and Zn(H) ions from ultrapure and river waters gave applicable results (> 90%) with high accuracy and precision. Thus, natural magnetite was found to be useful for the removal of these metal ions and its low toxicity, good biocompatibility, small size and being inexpensive makes it a good promising candidate material for water treatment studies.
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    The contents of sesamol and related lignans in sesame, tahina and halva as determined by a newly developed polarographic and stripping voltametric analysis
    Tokusoglu, O; Kocak, 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 (R-2=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.
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    Enhanced optical oxygen sensing using a newly synthesized ruthenium complex together with oxygen carriers
    Ertekin, K; Kocak, S; Ozer, MS; Aycan, S; Cetinkaya, B
    In this article, an emission based, simple and fast method is proposed for the determination of gaseous oxygen. A newly synthesized fluorophore dichloro-{2,6-bis[1-(4-dimethylamino-phenylimino) ethyl]pyridine} ruthenium(II) has been used for oxygen sensing together with oxygen carrier perfluorochemicals (PFCs) in silicon matrix. It should be noted that the solubility of oxygen in fluorocarbons is about three to ten times large as that observed in the parent hydrocarbons or in water. respectively. Employed PFCs are chemically and biochemically inert, have high dissolution capacities for oxygen. and, once doped into sensing film, considerably enhance the response of sensing agent. (C) 2003 Elsevier B.V. All rights reserved.
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    Platinum Nanoparticles/Poly(isoleucine) Modified Glassy Carbon Electrode for the Simultaneous Determination of Hydroquinone and Catechol
    Kocak, S
    A new electrochemical sensor based on Poly(Isoleucine) modified glassy carbon electrode decorated with platinum nanoparticles (Pt/Poly(Isoleucine)/GCE) was developed for sensitive individual and simultaneous determination of hydroquinone (HQ) and catechol (CC). Scanning electron microscopy (SEM), Electrochemical impedance spectroscopy (EIS), Cyclic voltammetry (CV) and Differential pulse voltammetry (DPV) were performed in order to characterize the Pt/Poly(Isoleucine)/GCE nanocomposite. For simultaneous determination of HQ and CC, Pt/Poly(Isoleucine)/GCE showed wide linear range between the 0.01-100.0 mu M. The detection limits were 0.006 mu M for HQ and 0.005 mu M for CC. The Pt/Poly(Isoleucine)/GC electrode exhibited good sensitivity and reliability in the simultaneous electroanalysis of two isomers in PBS of pH 7.5. The modified electrode was used to detect the isomers in naturel samples.
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    A novel ethanol biosensor on pulsed deposited MnOx-MoOx electrode decorated with Pt nanoparticles
    Ozdokur, KV; Demir, B; Atman, E; Tatli, AY; Yilmaz, B; Demirkol, DO; Kocak, S; Timur, S; Ertas, FN
    Transition metal oxides provide low cost alternatives to noble metals due to their unique electrocatalytic and electrochromic properties and display strong interactions with noble metal nanoparticles. Present study describes the use of mixed molybdenum and manganese oxide film electrode enriched with platinum nanoparticles to enhance the catalytic performance in the oxygen reduction reaction (ORR). The mixed oxide film, denominated as GCE/MnOx-MoOx/Pt, was co-deposited by pulsed potential deposition technique and then, it was used as an immobilization matrix for the intact bacterial cells. The resulted whole cell biosensor has served as a sensing platform for ethanol detection by monitoring of oxygen consumption as a result of the bacterial metabolism in the presence of the substrate. Following the optimization experiments, GCE/MnOx-MoOx/Pt/Gluconobacter oxydans biofilm was applied to investigate the analytical characteristics and response time to ethanol as well as operational stability and substrate specificity for other carbon sources. The linear range was found as 0.075-5.0 mM with a response time of 63 s and the developed method was applied to the ethanol determination in alcoholic drinks. Satisfactory recovery figures were obtained in comparison to the standard method. (C) 2016 Elsevier B.V. All rights reserved.