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    Flow injection analysis of sulphide based on its photoelectrocatalytic oxidation at poly-methylene blue modified glassy carbon electrode
    (Pergamon-Elsevier Science Ltd, 2012) Dilgin, Yusuf; Canarslan, Seda; Ayyildiz, Onder; Ertek, Bensu; Nisli, Gurel
    A new approach for photoelectrocatalytic determination of sulphide in a flow injection analysis (FIA) system was studied using a poly-methylene blue modified glassy carbon electrode (poly-MB/GCE). Results from electrochemical measurements have revealed that poly-MB/GCE is capable of signalling electrocatalytic and photoelectrocatalytic activity towards sulphide oxidation. When the surface of poly-MB/GCE was irradiated with a light source (250W Halogen lamp), the electrocatalytic current increased substantially. A homemade flow electrochemical cell with a suitable transparent window for the irradiation of the electrode surface was used to perform the photoelectrocatalytic determination of sulphide in FIA system. The currents obtained from the photoamperometric measurements in the FIA system at optimum conditions (carrier solution: pH 9.0 Britton Robinson buffer solution containing 0.1 M KCl; flow rate: 1.3 mL min(-1); transmission tubing length: 10 cm; injection volume: 100 mu L; and constant applied potential: +150 mV vs. Ag/AgCl/KClcat) were linearly correlated with the sulphide concentration. The calibration curves were obtained for sulphide concentrations in a range of 0.5-500 mu M. The detection limits were found to be 0.27 and 0.15 mu M for amperometric and photoamperometric methods, respectively. The proposed method was successfully applied to different wastewaters such as municipal sewage or tannery wastewater. Finally, results from the sulphide measurements by poly-MB/GCE were in good agreement with those attained using spectrophotometric method. Clown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.
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    Photoelectrocatalytic oxidation of NADH with electropolymerized Toluidine Blue O
    (Wiley-V C H Verlag Gmbh, 2007) Dilgin, Yusuf; Gorton, Lo; Nisli, Gurel
    A poly(Toluidine Blue O) (poly-TBO) modified electrode was successfully prepared by repeated sweeping the applied potential from -0.6 to + 0.8 V (vs. SCE) on a glassy carbon electrode (GCE) in borate buffer solution at pH 9.1 containing 0.1 M NaNO3 and 0.4 mM Toluidine Blue 0 (TBO). The poly-TBO modified GCE shows electrocatalytic activity toward NADH oxidation in phosphate buffer solution at pH 7.0, with an overpotential of ca. 350 mV lower than that at the bare electrode. The photoelectrocatalytic oxidation of NADH at this electrode was also successfully investigated by using cyclic voltammetry and amperometry at constant potential. When the modified electrode surface was irradiated with a 250 W halogen lamp, a photoelectrocatalytic effect was observed for NADH oxidation and the current was increased about 2.2 times. The applied potential was selected at +100mV for amperometric and photoamperometric detection of NADH. A linear calibration graph for NADH was obtained in the range between 1.0 x 10(-5) and 1.0 x 10(-3) M and between 5.0 x 10(-6) and 1.0 X 10(-3) M for amperometric and photoamperometric studies, respectively. The effect of some interfering compounds, such as ascorbic acid and dopamine on the electrocatalytic and photoclectrocatalytic oxidation of NADH was tested.