Yazar "Yagmur, Sultan" seçeneğine göre listele

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    Adsorption of Selected Amino Acids at the Mercury/Aqueous Solution Interface from the Chlorate (VII) and Its Dependence on the Supporting Electrolyte Concentration
    (Sage Publications Inc, 2015) Nosal-Wiercinska, Agnieszka; Grochowski, Mariusz; Wisniewska, Malgorzata; Tyszczuk-Rotko, Katarzyna; Yilmaz, Selehattin; Yagmur, Sultan; Saglikoglu, Gulsen
    In this study, we compared the adsorption of methionine, cysteine and cystine at the mercury/chlorate (VII) interface. Changes in the surface tension with the potential of the zero charge gamma(z) and relative surface excess Gamma' of methionine, cysteine and cystine as a function of their concentration indicate that the adsorption of the studied amino acids increases in the order of methionine > cystine > cysteine. For all the systems examined, linear dependences ln[x(1-Theta)/Theta = f(Theta)] (Frumkin isotherm) and ln (Gamma'/c) = f (Gamma') (virial isotherm) were obtained. Changes in the adsorption parameters as a function of the supporting electrolyte concentration indicate the competitive adsorption of amino acids and ClO4- ions and electrostatic interactions between the water dipoles and adsorbates in the double layer.
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    Determination of Ascorbic Acid in Tablet Dosage Forms and Some Fruit Juices by DPV
    (Esg, 2008) Yilmaz, Selehattin; Sadikoglu, Murat; Saglikoglu, Gulsen; Yagmur, Sultan; Askin, Gokce
    Ascorbic acid, a water-soluble vitamin, is the most common electroactive biological compound found in some fruit species. The electrochemical oxidation of ascorbic acid was investigated at glassy carbon electrode in various aqueous solutions in the pH range of 0.64-10.15 (in Britton-Robinson, acetate, phosphate buffers and 0.5 mol L-1 sulphuric acid solutions) by cyclic (CV) and differential pulse (DPV) voltammetry. For the quantitative purposes, a very well-resolved diffusion-controlled voltammetric peak was obtained in 0.2 mol L-1 acetate buffer (pH 3.49) at 0.342 V by DPV technique. The linear response was obtained in the concentration range of 6x10(-6)-8x10(-4) mol L-1 with a detection limit (LOD) of 5.17x10(-7) and quantitative limit (LOQ) of 1.72x10(-6) mol L-1. Ascorbic acid in pharmaceutical dosage forms and some fruit juices were determined by DPV. The reliability of the proposed voltammetric technique was established by recovery studies.
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    Direct Determination of Zn Heavy Metal in Tap Water of Canakkale (TURKEY) by Anodic Stripping Voltammetry Technique
    (Electrochemical Science Group, 2009) Yilmaz, Selehattin; Yagmur, Sultan; Saglikoglu, Gulsen; Sadikoglu, Murat
    In this work, the direct determination of zinc heavy metal in the tap water was carried out by differential pulse anodic stripping voltammetry (DPASV) technique at the glassy carbon electrode (GCE). The zinc ions were deposited by reduction at -1.5 V on a bare glassy carbon surface. Then, the deposited metal was oxidized by scanning the potential of the electrode surface from -1.5 to -0.8 volt using a differential puls mode. The stripping current arising from the oxidation of metal was connected with the concentration the metal in the sample. The concentration of zinc heavy metal found in tap water sample was determined to be 180 mu g L(-1) using 0.2 mol L(-1) acetate buffer (pH: 3.50).
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    Direct Quantitative Determination of Total Arsenic in Natural Hotwaters by Anodic Stripping Voltammetry at the Rotating Lateral Gold Electrode
    (Bentham Science Publ Ltd, 2009) Yilmaz, Selehattin; Baba, Baris; Baba, Alper; Yagmur, Sultan; Citak, Meryem
    A simple, rapid, selective and sensitive differential pulse anodic stripping voltammetric (DPASV) technique for the direct quantitative determination of inorganic total arsenic in natural hotwater was developed. The electrochemical determination of total arsenic has been carried out at the novel rotating lateral gold electrode in hydrochloric acid solution (37 % w/w). The analysis was performed with a special gold electrode whose active surface was located on the side. Reproductivity of measurement was achieved by the conditioning of the gold electrode. This was done every day before the measurements as well as when the background current varied strongly from measurement to measurement. The determination limit of 0.5 mu g L-1 was achieved with 10 mL sample solution. The total arsenic concentration was made by appropriate selection of the deposition potential. During the deposition step, the total arsenic content was reduced at -1200 mV by nascent hydogen to As degrees. During the subsequent voltammetric determination, the preconcentration As degrees was again oxidized to determine the level. The method was applied successfully to the direct quantitative determination of total inorganic arsenic in hotwater. In order to show the accuracy of the results developed from voltammetric technique, the values obtained were compared with those obtained from inductively coupled plasma mass spectrometry (ICP-MS).
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    Electroanalytical and HPLC Methods for the Determination of Oxcarbazepine in Spiked Human Urine and Tablet Dosage Form
    (Croatian Chemical Soc, 2014) Nosal-Wiercinska, Agnieszka; Yilmaz, Selehattin; Binel, Sevcan; Yagmur, Sultan; Saglikoglu, Gulsen; Sadikoglu, Murat; Yıldız, Mustafa
    In this study, the electrochemical reduction and determination of oxcarbazepine were easily realized in various buffer solutions in the pH range of 4.50 to 11.15 in real samples using glassy carbon electrode (GCE) by cyclic voltammetric (CV) and differential pulse voltammetric (DPV) techniques. The influence of pH on the cathodic peak current and peak potential was investigated. Scan rate studies were also completed. The diffusion controlled nature of the peak was established. The best results for the quantitative determination of oxcarbazepine were obtained by DPV technique in Britton-Robinson (BR) buffer (pH 8.05). In this basic medium, one irreversible and sharp cathodic peak was observed. A linear calibration curve for DPV analysis was constructed in the oxcarbazepine concentration range of 8x10(-6) to 1x10(-4) M. Limit of detection (LOD) and limit of quantification (LOQ) were obtained as 1.65x10(-6) and 5.51x10(-6) M, respectively. Repeatability, reproducibility, precision and accuracy of the developed technique were checked in spiked human urine and tablet dosage forms by recovery studies and results of the high performance liquid chromatography (HPLC) technique. A reduction mechanism for the electrode reaction was proposed.
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    Electroanalytical determination of metronidazole in tablet dosage form
    (Serbian Chemical Soc, 2013) Yilmaz, Selehattin; Baltaoglu, Esra; Saglikoglu, Gulsen; Yagmur, Sultan; Polat, Kamran; Sadikoglu, Murat
    In this study, the electrochemical reduction and determination of metronidazole were easily realized in Britton-Robinson buffer (pH 4.01) using an UTGE by cyclic voltammetric (CV) and differential pulse voltammetric (DPV) techniques. In this acidic medium, one irreversible and a sharp cathodic peak were observed. A linear calibration curve for DPV analysis was constructed in the metronidazole concentration range 3 x10(-6)-9x10(-5) mol L-1. The limit of detection (LOD) and limit of quantification (LOQ) were 1.42x10(-7) and 4.76x10(-7) mol L-1 respectively.
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    Electrochemical oxidation of prednisolone at glassy carbon electrode and its quantitative determination in human serum and tablets by Osteryoung square wave voltammetry
    (Bentham Science Publ Ltd, 2007) Yilmaz, Selahattin; Skrzypek, Slowomira; Dilgin, Yusuf; Yagmur, Sultan; Coskun, Mahmut
    A simple, rapid, selective and sensitive electrochemical method for the direct determination of prednisolone in spiked human serum and tablets was developed. The electrochemical oxidation and determination of prednisolone has been carried out at glasy carbon electrode (GCE) in various aquaeous solution in the pH range of 0.56-12.30 by cyclic (CV) and Osteryoung square wave voltammetry (OSWV). The best results were obtained for the determination of prednisolone by OSWV method in 0.5 mol L-1 sulphuric acid at about pH 0.56. The peak current and peak potential depends on pH, so its influence and also scan rate were studied. The diffusion controlled by nature of the peak was established. This electroanalytical procedure enabled to determine prednisolone in the concentration range 1.0 X 10(-6)- 2.0 x 10(-5) mol L-1. This limit of detection (LOD) and limit of quantification (LOQ) were obtained as 3.4x10(-7) and 4.5x 10(-7) mol L-1 respectively. Precision and accuracy of the developed method were checked by recovery studies in spiked tablets and human serum.
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    Electrochemical Reduction of Phenazopyridine Hydrochloride in Dimetyl Sulfoxide
    (Gazi Univ, 2012) Yagmur, Sultan; Yilmaz, Selehattin
    In the present work, the electrochemical reduction of phenazopyridine hydrochloride (PAP) was carried out on glassy carbon (GCE) electrode in different supporting electrolyte/solvent systems by cyclic voltammetric (CV) technique. The best results for PAP were obtained in 0.1 M tetrabutyammonium iodide/dimetyl sulfoxide (TBAI/DMSO) non-aqueous system by CV technique. In this media, three irreversible cathodic peaks were observed about -0.7 V, -1.7 V and -2.0 V for PAP. With the scan rate measurements the process was found diffusion controlled. The possible reduction mechanism of PAP was also discussed.
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    Impact of water activity on double layer parameters at the mercury/chlorates(VII) interface in the presence of mixed adsorption layers of 6-mercaptopurine-Triton X-100
    (Springer, 2019) Nosal-Wiercinska, Agnieszka; Kaliszczak, Waldemar; Drapsa, Anna; Wisniewska, Malgorzata; Yilmaz, Selehattin; Yagmur, Sultan; Saglikoglu, Gulsen
    Adsorption mechanism of 6-mercaptopurine, 6-mercaptopurine-Triton X-100 on the mercury electrode surface from 2, 4 and to 6 mol dm(-3) chlorates(VII) was studied as the function of adsorbate bulk concentration. The experimental data obtained from the measurements of differential capacity of the double layer were used, namely the measurements of zero charge potential and surface tension at the zero charge potential. In the case of mixed adsorption layer of 6-mercaptopurine-Triton X-100 domination of 6MP in adsorption equilibria formation as well as competitive adsorption between the 6-mercaptopurine-Triton X-100 molecules were found. Significant contribution of water molecules in the adsorption-desorption processes was also observed.
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    Osteryoung square wave voltammetric determination of phenazopyridine hydrochloride in human urine and tablet dosage forms based on electrochemical reduction at carbon paste electrode
    (Bentham Science Publ Ltd, 2007) Citak, Meryem; Yilmaz, Selahattin; Dilgin, Yusuf; Tuerker, Guelen; Yagmur, Sultan; Erdugan, Hueseyin; Erdugan, Necla
    An electroanalytical method was developed for the direct quantitative determination of phenazopyridine hydrochloride (PAP) or in other words, pyridium, in spiked human urine and tablet dosage forms. The electrochemical reduction and determination of PAP were carried out at carbon paste electrode (CPE) in various aquaeous Solution in the pH range of 0.5-12.30 by (CV) and osteryoung square wave voltammetry (OSWV). The best results were obtained for the quantitative determination of PAP by OSWV method in 0.5 mol L-1 Sulfuric acid at about pH 0.51. The peak current and peak potential depend on pH and scan rate were studied. The diffusion controlled nature of the peak was established. This electroanalytical procedure made it possible to determine PAP in the concentration range 2.5x10(-8)-2.5x10(-6) mol L-1. Limit of detection (LOD) and limit of quantification (LOQ) were obtained as 7.5x10(-9) and 2.5x10(-8) mol L-1 respectively. Precision and accuracy of the developed method were checked by recovery studies in spiked urine and tablet dosage forms.
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    Sensitive voltammetric determination of famotidine in human urine and tablet dosage forms using an ultra trace graphite electrode
    (Serbian Chemical Soc, 2014) Yagmur, Sultan; Yilmaz, Selehattin; Saglikoglu, Gulsen; Uslu, Bengi; Sadikoglu, Murat; Ozkan, Sibel A.
    In this study, the direct and sensitive determination of famotidine based on its electrochemical oxidation was investigated in spiked human urine and tablet dosage forms. The electrochemical measurements were performed in various buffer solutions in the pH range 0.88-12.08 at an ultra trace graphite electrode (UTGE) by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The best results were obtained for the quantitative determination of famotidine by the DPV technique in 0.5 mol L-1 H2SO4 solution (pH 0.30). In this strong acid medium, one irreversible anodic peak was observed. The effects of pH and scan rate on the peak current and peak potential were investigated. The diffusion-controlled nature of the peak was established. For optimum conditions described in the experimental section, a linear calibration curve for DPV analysis was constructed in the famotidine concentration range 2x10(-6)-9x10(-5) mol L-1. The limit of detection (LOD) and limit of quantification (LOQ) were 3.73x10(-7) and 1.24x10(-6) mol L-1 at a UTGE, respectively. The repeatability, precision and accuracy of the developed technique were checked by recovery studies in spiked urine and tablet dosage forms.
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    Sensitive Voltammetric Determination of Paracetamol on Poly(4-Aminobenzene Sulfonic Acid) Modified Glassy Carbon Electrode
    (Esg, 2016) Yilmaz, Selehattin; Bas, Zeynep; Sadikoglu, Murat; Yagmur, Sultan; Saglikoglu, Gulsen
    A poly (4-aminobenzene sulfonic acid) (4-ABSA) modified glassy carbon electrode (GCE) was prepared for the quantitative determination of paracetamol (PCT). The 4-ABSA-modified GCE was prepared by electrochemical polymerization method in phosphate buffer solution (PBS) (pH 7.0). The polymer film-modified electrode has high catalytic ability for electrooxidation of PCT, which appeared at pH range of 5-8 by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The best results for the determination of PCT were obtained by DPV in PBS (pH 7.00). Calibration curve was obtained in the PCT concentration range of 6x10(-7) to 9x10(-6) mol L-1 by DPV. Limit of detection (LOD) and quantification (LOQ) were found as 9.33x10(-8) mol L-1 and 3.10x10(-7) mol L-1, respectively. The results of experiments indicated that modified electrode have good stability, sensitivity and reproducibility for at least one month if stored dry in air.
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    Synthesis, spectroscopic studies and electrochemical properties of Schiff bases derived from 2-hydroxy aromatic aldehydes and phenazopyridine hydrochloride
    (Serbian Chemical Soc, 2013) Yagmur, Sultan; Yilmaz, Selehattin; Saglikoglu, Gulsen; Sadikoglu, Murat; Yıldız, Mustafa; Polat, Kamran
    Novel Schiff bases 1-4 were synthesized by the reaction of 2-hydroxybenzaldehyde, 2-hydroxy-5-methoxybenzaldehyde, 2-hydroxy-5-nitrobenzaldehyde and 2-hydroxy-1-naphthaldehyde with phenazopypridine hydrochloride (PAP), respectively, and their structures were elucidated by means of spectroscopic techniques. The electrochemical reduction of PAP and its Schiff bases (1-4) were realized on a glassy carbon electrode (GCE) in dimethyl sulfoxide (DMSO) using the cyclic voltammetric (CV) technique. The effect of functional groups on reduction potential of the Schiff bases was investigated. A general electrochemical reduction mechanism of the compounds is suggested.
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    Voltammetric Determination of Acyclovir in Human Urine Using Ultra Trace Graphite and Glassy Carbon Electrodes
    (Bentham Science Publ Ltd, 2011) Sadikoglu, Murat; Saglikoglu, Gulsen; Yagmur, Sultan; Orta, Erdem; Yilmaz, Selehattin
    An electroanalytical method was developed for the direct quantitative determination of Acyclovir (Acy) in spiked human urine base on its oxidation behavior. The electrochemical oxidation and determination of Acy were easily carried out on ultra trace graphite electrode (UTGE) and glassy carbon electrode (GCE) using a variety of voltammetric techniques. The electrochemical measurements were carried out on these electrodes in various buffer solutions in the pH range of 3.66 to 9.08 by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The best results for the quantitative determination of Acy were obtained by DPV technique in 0.2 M acetate buffer (pH=4.66). In this acidic medium, one irreversible anodic peak was observed. The anodic peak current and peak potential depend on pH and scan rate were studied. The diffusion controlled nature of the peak was established. Acy was determined in the concentration range from 4x10(-6) to 7x10(-5) molL(-1) for UTGE and 2.0x10(-6) to 1.0x10(-4) molL(-1) for GCE by the applied electroanalytical procedure. Limit of detection (LOD) and limit of quantification (LOQ) were obtained as 1.0x10(-6) and 3.3x10(-6) molL(-1) on UTGE and 3.5x10(-7) and 1.2x10(-6) molL(-1) on GCE, respectively. Repeatability, precision and accuracy of the developed technique were checked by recovery studies in spiked urine.