Browsing by Author "Yardim, Y."

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Electrochemical Behavior of Folic Acid at a Boron-Doped Diamond Electrode: Its Adsorptive Stripping Voltammetric Determination in Tablets
(Turkish Pharmacists Association, 2014) Yardim, Y.; Şentürk, Z.
The electrochemical properties of folic acid were investigated in pH range 1.0-9.0 by cyclic, linear sweep and adsorptive stripping voltammetry. The compound was irreversibly oxidized at an anodically pretreated boron-doped diamond electrode in one or two oxidation steps, which are concentration- and/or pH-dependent. Using square-wave stripping mode, folic acid yielded well-defined voltammetric responses in both 0.1M perchloric acid and 0.1M Britton-Robinson buffer, pH 6.0 with limits of detection 0.035 μg/mL (7.93 10-8 M) and 0.14 μg/mL (3,2 × l0-7 M), respectively, after an accumulation of 120 s at open-circuit condition. Practical applicability of the newly developed approach was verified by the direct assays of tablet dosage forms.
Electrochemical Oxidation of Ranitidine at Poly(Dopamine) Modified Carbon Paste Electrode: Its Voltammetric Determination in Pharmaceutical and Biological Samples Based on the Enhancement Effect of Anionic Surfactant
(Elsevier Science Sa, 2018) Pinar, P. Talay; Yardim, Y.; Senturk, Z.
The preparation and characterization of a carbon paste electrode modified with poly(dopamine) as well as its novel application for the electrochemical oxidation and voltammetric determination of ranitidine are described. The sensitivity of the voltammetric measurements was significantly increased at modified electrode in comparison to the bare one. Besides, a further increase in the detecting sensitivity of ranitidine could be obtained in the presence of anionic surfactant (sodium dodecylsulfate). Using square-wave voltammetry, the drug yielded a well-defined voltammetric response in Britton-Robinson buffer (pH 5.0) containing 1 x 10(-3) M sodium dodecylsulfate at + 0.96 V (vs. Ag/AgCl). The process could be used to determine ranitidine in the concentration range from 1 x 10(-7) to 7.5 x 10(-6) M, with a detection limit of 1.9 x 10(-8) M (6.1 ng mL(-1)). The suggested method was successfully applied to pharmaceuticals and spiked human urine samples.
Trace Determination of Dna in an Amaryllidaceae Plant, Narcissus Tazetta by Square-Wave Stripping Voltammetry Based on Guanine Signal
(2007) Yardim, Y.; Şentürk, Z.; Özsöz, M.; Özdemir, K.; Atalan, E.
This study is, to our knowledge, the first application of electrochemical DNA biosensor for the quantification of DNA in plant extracts. The DNA biosensor was assembled by immobilizing the double-stranded fish sperm DNA on the surface of a singleuse pencil graphite electrode. Square-wave voltammetric method with the baseline correction was carried out to evaluate the oxidation signal of the guanine base. The experimental variables such as solution pH, buffer concentration, immobilization time, stirring speed, and square-wave parameters were optimized. The extremely low detection limit (0.36 ng/mL) was coupled to a good surface-to-surface reproducibility (a relative standard deviation of 8.4% for 7 repetitive measurements of 40 ng/mL). The renewable and low-cost DNA biosensor developed in this study using pencil graphite electrode was applied to the determination of DNA isolated from an Amaryllidaceae plant, Narcissus tazetta.
Voltammetric Measurement of Catechol-O Inhibitor Tolcapone in the Pharmaceutical Form on the Boron-Doped Diamond Electrode
(TUBITAK, 2024) Kiran, M.; Yardim, Y.
This study presents an electroanalytical approach to measure the catechol-O-methyltransferase (COMT) inhibitor tolcapone (TOL) using a boron-doped diamond (BDD) electrode. The application of cyclic voltammetry (CV) technique revealed that TOL exhibited a distinct, diffusion-controlled, irreversible anodic peak at a potential of approximately +0.71 V (vs. Ag/AgCl) in a 0.1 mol L–1 phosphate buffer solution (PBS) with a pH of 2.5. The oxidation of TOL is highly dependent on the pH and supporting electrolytes. Based on the data obtained from the pH investigation, a proposed mechanism for the electro-oxidation of TOL is suggested. Using the square wave voltammetry (SWV) technique, a satisfactory linear relationship was observed at approximately +0.66 V in a 0.1 mol L–1 PBS with a pH of 2.5. The presented method exhibited linearity within the concentration range between 1.0–50.0 μg mL–1 (3.7 × 10–6–1.8 × 10–4 mol L–1), with a limit of detection (LOD) of 0.29 μg mL–1 (1.1 × 10–6 mol L–1). The BDD electrode demonstrated good selectivity against inorganic ions and filler materials interference. Finally, the suitability of the developed approach was assessed by measuring TOL in tablet formulations, resulting in favorable recoveries ranging from 103.4% to 106.2%. Copyright This work is licensed under a Creative Commons Attribution 4.0 International License.
Voltammetric Studies on the Potent Carcinogen, 7,12-Dimethylbenz[a]anthracene: Adsorptive Stripping Voltammetric Determination in Bulk Aqueous Forms and Human Urine Samples and Detection of Dna Interaction on Pencil Graphite Electrode
(Elsevier, 2010) Yardim, Y.; Keskin, E.; Levent, A.; Ozsoz, M.; Senturk, Z.
7,12-Dimethylbenz[a]anthracene (DMBA), is a widely studied polycyclic aromatic hydrocarbon that has long been recognized as a very potent carcinogen. Initially, the electrochemical oxidation of DMBA at the glassy carbon and pencil graphite electrodes in non-aqueous media (dimethylsulphoxide with lithium perchlorate) was studied by cyclic voltammetry. DMBA was irreversibly oxidized in two steps at high positive potentials, resulting in the ill-resolved formation of a couple with a reduction and re-oxidation wave at much lower potentials. Special attention was given to the use of adsorptive stripping voltammetry together with a medium exchange procedure on disposable pencil graphite electrode in aqueous solutions over the pH range of 3.0-9.0. The response was characterized with respect to pH of the supporting electrolyte, pre-concentration time and accumulation potential. Using square-wave stripping mode, the compound yielded a well-defined voltammetric response in acetate buffer, pH 4.8 at +1.15V (vs. Ag/AgCl)(a pre-concentration step being carried out at a fixed potential of +0.60 V for 360 s). The process Could be used to determine DMBA concentrations in the range 2-10 nM, with an extremely low detection limit of 0.194 nM (49.7 ng L-1). The applicability to assay of spiked human urine samples was also illustrated. Finally, the interaction of DMBA with fish sperm double-stranded DNA based on decreasing of the oxidation signal of adenine base was studied electrochemically by using differential pulse voltammetry with a pencil graphite electrode at the surface and also in solution. The favorable signal-to-noise characteristics of biosensor resulted in low detection limit (ca. 46 nM) following a 300-s interaction. These results displayed that the electrochemical DNA-based biosensor could be used for the sensitive, rapid. simple and cost effective detection of DMBA-DNA interaction. (C) 2009 Elsevier B.V. All rights reserved.