Browsing by Author "Yigit, Aydin"

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Electrochemical Determination of Pterostilbene at a Cathodically Pretreated Boron-Doped Diamond Electrode Using Square-Wave Adsorptive Anodic Stripping Voltammetry in Cationic Surfactant Media
(Elsevier Science Sa, 2016) Yigit, Aydin; Yardim, Yavuz; Zorer, Ozlem Selcuk; Senturk, Zuhre
In the present paper, an electrochemical method was developed for the determination of pterostilbene (a phenolic phytoalexin) using adsorptive anodic stripping voltammetry at a cathodically pretreated boron doped diamond electrode. The oxidation of compound was irreversible and exhibited an adsorption controlled process which is of pH dependence. The sensitivity of the stripping voltammetric measurements was significantly improved in the presence of cationic surfactant, cetyltrimethylammonium bromide (CTAB). Using square-wave stripping mode, a highly linear analytical curve was obtained for pterostilbene determination in 0.1 M HNO3 solution containing 2 x 10(-4)M CTAB at +0.78V (vs. Ag/AgCl) (after 30 s accumulation at open-circuit condition). The process could be used in the range of 0.005-1.0 mu g mL(-1) (2.0 x 10(-8)-3.9 x 10(-6)M), with a detection limit of 0.0011 mu gmL(-1) (4.3 x 10(-9) M). The proposed method was successfully applied to measure the concentration of pterostilbene in the commercial dietary supplements, with results similar to those obtained using a HPLC method at 95% confidence level. As far as it could be verified, the proposed method is the first one based on the electrochemical investigation of pterostilbene. (C) 2016 Elsevier B.V. All rights reserved.
A Graphene-Based Electrochemical Sensor for the Individual, Selective and Simultaneous Determination of Total Chlorogenic Acids, Vanillin and Caffeine in Food and Beverage Samples
(Wiley-v C H verlag Gmbh, 2018) Yigit, Aydin; Alpar, Nurcan; Yardim, Yavuz; Celebi, Metin; Senturk, Zuehre
An electrochemical sensor based on the electrocatalytic activity of graphene (GR) was prepared, and used for the individual, selective and simultaneous determination of 5-O-Caffeoylquinic acid (5-CQA) that is major compound of chlorogenic acids in coffee, vanillin (VAN) and caffeine (CAF). The electrochemical behaviors of these compounds on GR modified glassy carbon electrode (GR/GCE) were investigated by cyclic voltammetry and square-wave adsorptive stripping voltammetry. By using stripping conditions after 30s accumulation under open-circuit voltage, the electrochemical oxidation peaks appeared at +0.53, 0.83 and 1.39V in phosphate buffer pH2.5, and good linear current responses were obtained with detection limits of 4.4x10(-9), 5.0x10(-7), and 3.0x10(-7)M for 5-CQA, VAN and CAF, respectively. The potential applicability of the proposed method was illustrated in commercial food and beverage samples.
Graphene/Nafion Composite Film Modified Glassy Carbon Electrode for Simultaneous Determination of Paracetamol, Aspirin and Caffeine in Pharmaceutical Formulations
(Elsevier Science Bv, 2016) Yigit, Aydin; Yardim, Yavuz; Celebi, Metin; Levent, Abdulkadir; Senturk, Zuhre
A graphene-Nafion composite film was fabricated on the glassy carbon electrode (GR-NF/GCE), and used for simultaneous determination of paracetamol (PAR), aspirin (ASA) and caffeine (CAF). The electrochemical behaviors of PAR, ASA and CAF were investigated by cyclic voltammetry and square-wave adsorptive anodic stripping voltammetry. By using stripping one for simultaneous determination of PAR, ASA and CAF, their electrochemical oxidation peaks appeared at +0.64,1.04 and 1.44 V, and good linear current responses were obtained with the detection limits of 18 ng mL(-1) (1.2 x 10(-9) M), 11.7 ng mL(-1) (6.5 x 10(-8) M) and 7.3 ng mL(-1) (3.8 x 10(-8) M), respectively. Finally, the proposed electrochemical sensor was successfully applied for quantifying PAR, ASA and CAF in commercial tablet formulations. (C) 2016 Elsevier B.V. All rights reserved.
Square-Wave Adsorptive Stripping Voltammetric Determination of Hesperidin Using a Boron-Doped Diamond Electrode
(Pleiades Publishing inc, 2020) Yigit, Aydin; Yardim, Yavuz; Senturk, Zuhre
In the present study, an electroanalytical method for the determination of hesperidin using adsorptive stripping voltammetry at an unmodified boron-doped diamond (BDD) electrode is presented. In cyclic voltammetry, the compound showed one irreversible and adsorption-controlled oxidation peak, resulting in the formation of a couple with a reduction and re-oxidation wave at less positive potentials. Using square-wave stripping mode, the observed anodic peak current in 0.1 M perchloric acid solution at +0.90 V (vs. Ag/AgCl) (after 30 s accumulations at a fixed potential of +0.4 V) increased linearly from 2.5 to 70 mu g/mL (4.09 x 10(-6)-1.15 x 10(-4) M). A detection limit of 0.7 mu g/mL (1.2 x 10(-6) M) and relative standard deviation of 8.2% for the concentration of 2.5 mu g/mL (n = 10) were observed. To evaluate the practical applicability of the BDD electrode, it was used for the quantification of hesperidin in the commercial dietary supplement formulations.
Voltammetric Sensor Based on Boron-Doped Diamond Electrode for Simultaneous Determination of Paracetamol, Caffeine, and Aspirin in Pharmaceutical Formulations
(Ieee-inst Electrical Electronics Engineers inc, 2016) Yigit, Aydin; Yardim, Yavuz; Senturk, Zuhre
In this paper, a method was developed for the individual and simultaneous determination of paracetamol (PAR), caffeine (CAF), and aspirin (ASA), based on the oxidation of these compounds at a cathodically pretreated boron-doped diamond electrode without any chemical modification. The electrochemical behavior of these three molecules was investigated employing cyclic voltammetry and square-wave adsorptive stripping voltammetry. Using stripping voltammetry in phosphate buffer at pH 2.5, the three compounds can well separate from each other with the potential differences of 0.71, 1.27, and 0.56 V among PAR-CAF, PAR-ASA, and CAF-ASA, respectively, which are large enough to determine PAR, CAF, and ASA individually and simultaneously. After the optimization of analytical conditions employing this electrode in phosphate buffer (pH 2.5), the adsorptive stripping peak currents for the three molecules were found to be linearly with their concentrations in the range of 5-125 mu g mL(-1) with the detection limits of 0.597, 0.277, and 1.310 mu g mL(-1) for PAR, CAF, and ASA, respectively. The presented method was provided a fast, sensitive, and simple approach to the determination of PAR, CAF, and ASA in the pharmaceutical formulations. The results obtained were statistically analyzed and compared with those obtained by applying the high-performance liquid chromatographic method with diode-array detection.