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    DETERMINATION OF ANTI-CANCER DRUG EMODIN USING A SILICA-GEL-MODIFIED CARBON PASTE ELECTRODE
    (Soc Brasileira Quimica, 2014) Vu, Dai Long; Ertek, Bensu; Dilgin, Yusuf; Cervenka, Libor
    In this paper, a silica-gel-modified carbon paste electrode (Si-gel/ CPE) was used to determine the anti-cancer drug emodin by anodic stripping differential pulse voltammetry (ASDPV). The effects of the silica-gel content, the pH of the supporting electrolyte, and the scan rate on the oxidation current of emodin were investigated. The oxidation currents of emodin obtained from ASDPV measurements were linearly correlated with the concentration in the range of 5.0 x 10(-9) to 300.0 x 10(-9) mol L-1. The limit of detection was determined to be 1.5 x 10(-9) mol L-1. The current method was successfully applied to determine emodin in a knotweed root sample, with recovery rate of 92.5% to 98.3%.
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    Flow Injection Amperometric Detection of Sulfide Using a Prussian Blue Modified Glassy Carbon Electrode
    (Japan Soc Analytical Chemistry, 2012) Ertek, Bensu; Vu, Dai Long; Cervenka, Libor; Dilgin, Yusuf
    This study investigates a new approach for the electrocatalytic determination of sulfide in a flow injection analysis (FIA) system using a Prussian blue modified glassy carbon electrode (PB/GCE). The results from experiments show that PB/GCE significantly enhances the electrocatalytic activity towards sulfide oxidation. A homemade flow electrochemical cell was used to perform the electrocatalytic determination of sulfide in the FIA system. The currents obtained from amperometric measurements in the HA system at optimum conditions (carrier solution, pH 8.0; Britton-Robinson buffer solution containing 0.1 M KCl; flow rate, 1.4 mL/min; transmission tubing length, 10 cm; injection volume, 100 mu L; constant applied potential, +150 mV vs. Ag/AgCl/KClsat) were linearly correlated with the sulfide concentration. A calibration curve was obtained for sulfide concentrations in the range of 0.5 - 100 mu M. The detection limit was found to be 0.3 mu M for the amperometric method. The proposed method was successfully applied to wastewater sample. Finally, results from sulfide measurements by PB/GCE were in good agreement with those obtained from the spectrophotometric method.
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    Sensitive Voltammetric Determination of Natural Flavonoid Quercetin on a Disposable Graphite Lead
    (Faculty Food Technology Biotechnology, 2015) Vu, Dai Long; Zabcikova, Simona; Cervenka, Libor; Ertek, Bensu; Dilgin, Yusuf
    In this paper, a pencil graphite electrode was pretreated using chronoamperometry technique in phosphate buffer solution (pH=7.0) for sensitive determination of quercetin. Oxidation of quercetin was investigated using pretreated pencil graphite electrode and anodic stripping differential pulse voltammetry. Under optimal conditions, the anodic current of quercetin exhibited linear response to its concentration in the range from 0.001 to 1.5 mu mol/L with the limit of detection of 0.3.10(-3) mu mol/L. The proposed method was successfully applied for the determination of quercetin in cranberry and blackcurrant juices with recovery rate from 93.2 to 94.7 %. Solid-phase extraction was found to be necessary prior to voltammetric determination of quercetin in fruit juice samples using pretreated pencil graphite electrode.
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    Voltammetric Determination of Tannic Acid in Beverages using Pencil Graphite Electrode
    (Czech Academy Agricultural Sciences, 2015) Vu, Dai Long; Ertek, Bensu; Dilgin, Yusuf; Cervenka, Libor
    The pretreated pencil graphite electrode (Pre-PGE) prepared by a chronoamperometry technique was applied for the determination of tannic acid using anodic stripping differential pulse voltammetry. The currents obtained from voltammetry measurements at optimum conditions were linearly correlated with the concentration of tannic acid. Calibration curve was obtained for tannic acid in the concentration range of 5.0-500 x 10(-9) mol/l. The limit of detection was found to be 1.5 x 10(-9) mol/l. The content of tannic acid in beverage samples determined with Pre-PGE was in good agreement with that obtained by the standard spectrophotometric method.