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Öğe Electrochemical performance of boron-doped diamond electrode in surfactant-containing media for ambroxol determination(Elsevier, 2014-07-17) Levent, Abdulkadir; Yardım, Yavuz; Şentürk, ZühreA novel application of boron-doped diamond electrode is introduced for the determination of ambroxol, a potential antioxidant drug belonging to the expectorant class. The electrochemical oxidation of ambroxol was first investigated by cyclic voltammetry using boron-doped diamond and glassy carbon electrodes in aqueous solutions both with and without the addition of surfactant. The compound was irreversibly oxidized in one/two steps at high positive potentials, resulting in the formation of a couple with a reduction and re-oxidation wave at less positive potentials. Special attention was given to the use of adsorptive stripping voltammetry at a surface of mildly oxidized boron-doped diamond electrode in aqueous solutions over the pH range of 1.0–10.0. Addition of anionic surfactant (sodium dodecylsulfate) to ambroxol-containing electrolyte enhanced the stripping current signal. Using square-wave stripping mode, the drug yielded a well-defined voltammetric response in phosphate buffer pH 2.5 containing 4 × 10−4 M sodium dodecylsulfate at +1.02 V (versus Ag/AgCl) (after 30 s accumulation at +0.50 V). The process could be used to determine ambroxol in the concentration range of 0.05–0.7 μM, with a detection limit of 0.010 μM (4.2 ng mL−1). The suggested method was successfully applied to pharmaceuticals and spiked human urine samples.Öğe Electroanalytical determination of progesterone hormone using borondoped diamond electrode(ICNTC, 2020) Levent, Abdulkadir; Uçar, MuhlisProgesterone is synthesized from pregnenolone, a derivative of cholesterol like other steroids. It is a steroid hormone that has a vital importance in human and animal health. In case of progesterone imbalance, it causes problems such as fertility and infertility. In this study, electrochemical properties of Progesterone hormone Boron doped diamond (BDD) on electrode surface were investigated in strongly acidic environment (HClO4 and H2SO4). A fast, sensitive, selective and simple electroanalytical method was developed for cathodically pre-treated BDD electrodes. A good linear analytical curve in the concentration range of 10 μM to 100 μM at a voltage value of +1.51 V (vs. Ag / AgCl) (after 120 s deposition at +0.1 V voltage) in 0.5 M HClO4 using the square wave stripping technique for the quantification of progesterone hormone obtained. The observability limit is 0.012 µM(3.77 µg L-1); The relative standard deviation value (RSD) for the concentration of 3.1 µM (n = 11) was calculated to be 4.87%. In addition, the developed voltammetric method has been successfully applied to drug and blood serum.Öğe Electrochemical determination of melatonin hormone using a boron-doped diamond electrode(Elsevier, 2012-01) Levent, AbdulkadirIn this study, a boron-doped diamond electrode was used for the electroanalytical determination of melatonin in the pharmaceutical tablet and urine samples by square-wave voltammetry. Melatonin yielded a well-defined voltammetric response in Britton-Robinson buffer, pH 3.0 at + 0.88 V (vs. Ag/AgCl). Using the optimal square-wave voltammetry conditions, the oxidation peak was used to determine melatonin in the concentration range of 5.0 × 107 M to 4.0 × 106 M (r = 0.998, n = 8), a detection limit of 1.1 × 107 M (0.025 μg/mL) and relative standard deviation was 2.06% at the 2.0 × 106 M level (n = 10). Recoveries of melatonin were in the range of 97.67–105%, for both tablet and spiked human urine samples.Öğe Voltammetric behavior of benzo[a]pyrene at boron-doped diamond electrode: A study of its determination by adsorptive transfer stripping voltammetry based on the enhancement effect of anionic surfactant, sodium dodecylsulfate(Elsevier, 2011-07-15) Yardım, Yavuz; Keskin, Ertuğrul; Levent, Abdulkadir; Şentürk, ZühreBenzo[a]pyrene (BaP), a member of the polycyclic aromatic hydrocarbon (PAH) class, is one of the most potent PAH carcinogens. The electrochemical oxidation of BaP was first studied by cyclic voltammetry at the boron-doped diamond electrode in non-aqueous solvent (dimethylsulphoxide with lithium perchlorate). The compound was irreversibly oxidized in a single step at high positive potential, resulting in the well-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 in aqueous and aqueous/surfactant solutions over the pH range of 2.0–8.0. The technique in aqueous solutions had little value in practice because of too small oxidation peak current. This problem was solved when surfactants were added into the sample solution, by which the oxidation peak currents of BaP were found enhanced dramatically. The employed surfactants were sodium dodecylsulfate (anionic, SDS), cetyltrimethylammonium bromide (cationic, CTAB) and Tween 80 (non-ionic). Using square-wave stripping mode, the compound yielded a well-defined voltammetric response in Britton–Robinson buffer, pH 2.0 containing 2.5 × 10−4 M SDS at +1.07 V (vs. Ag/AgCl) (after 120 s accumulation at +0.10 V). The process could be used to determine BaP in the concentration range of 16–200 nM (4.04–50.46 ng mL−1), with a detection limit of 2.86 nM (0.72 ng mL−1). This method was also applied to determine BaP in model water sample prepared by adding its different concentrations into tap water.
