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Öğe Voltammetric behavior of testosterone on bismuth film electrode: Highly sensitive determination in pharmaceuticals and human urine by square‐wave adsorptive stripping voltammetry(Wiley Online Library, 2015-03-20) Levent, Abdulkadir; Altun, Ahmet; Taş, Süleyman; Yardım, Yavuz; Şentürk, ZühreIn this paper, an electrochemical application of bismuth‐film electrode (BiFE) fabricated via ex‐situ electrodeposition onto a glassy carbon electrode for testosterone determination was investigated in aqueous and aqueous/surfactant solutions. In cyclic voltammetry, the compound showed one irreversible and adsorption‐controlled reduction peak. The BiFE revealed good linear response in the examined concentration range of 1 to 45 nmol L−1 testosterone in BrittonRobinson buffer, pH 5.0 containing 3 mmol L−1 cetyltrimethylammonium bromide. The limit of detection was 0.3 nmol L−1 (0.09 ng mL−1). Finally, the BiFE was satisfactorily applied for quantitation of testosterone in both pharmaceutical (oil‐based ampoule) and biological (human urine) samples.Öğe Electrooxidation of thiourea and its square-wave voltammetric determination using pencil graphite electrode(Walter de Gruyter, 2011-04-01) Levent, Abdulkadir; Keskin, Ertuğrul; Yardım, Yavuz; Şentürk, ZühreThe electrochemical properties of thiourea (TU) were investigated in pH range 2.0-12.0 by cyclic and square-wave voltammetry. The compound was irreversibly oxidized at a pencil graphite electrode in one or two oxidation steps which are pH-dependent. Based on the voltammetric peak for the second oxidation process of TU in phosphate buffer at pH 12.0, a square-wave voltammetric method was proposed for the determination of the compound in the range 6.3-30μm, with a detection limit of 1.29μm. The applicability to direct assays of wastewaters was also tested.Öğe Protective effect of Hypericum perforatum L. on serum and hair trace elements in rats 7,12-dimethylbenz[a]anthracene-induced oxidative stress(Elsevier, 2012-02-08) Ekin, Suat; Yardım, Yavuz; Oto, Gökhan; Levent, Abdulkadir; Özgökçe, Fevzi; Kusman, TubaThe study was designed to assess the effect of Hypericum perforatum L. (H.P) on serum and hair trace elements and mineral levels, oral administration of 7,12-dimethylbenz[a]anthracene (DMBA) induced oxidative stress in Sprague-Dawley female rats. Analysis of the trace element has been carried out using atomic absorption spectrophotometer method at end of 60th day. It has been found out that the DMBA group contained statistically lower Zn and Cr compared to the control group (p < 0.01) and (p < 0.05), Cu, Mg and Na contained higher than control group (p < 0.05), (p < 0.05) and (p < 0.05). In DMBA + H.P group, Zn higher and Na lower than DMBA group (p < 0.05), (p < 0.05), in hair samples Cd, K and Zn contained lower DMBA compared to the control group (p < 0.05), (p < 0.05) and (p < 0.05). In group DMBA + H.P, Cd was higher than DMBA group and Cr lowered accordance with control group (p < 0.05). The present study demonstrated significantly positive and beneficial effect of H.P on the concentration levels of Zn and Na in serum, also on Cd levels in hair between DMBA and DMBA + H.P groups.
