Browsing by Author "Senturk, Zuehre"

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Development of an Ion-Pair Hplc Method for Determination of Acebutolol in Pharmaceuticals
(Taylor & Francis inc, 2010) Levent, Abdulkadir; Senturk, Zuehre
A simple and accurate ion-pair reversed-phase high-performance liquid chromatographic (RP-HPLC) method has been developed and validated for determination of acebutolol (ACE) in tablet dosage forms. Both ACE and ambroxol (internal standard) were well separated using a reversed phase column and a mobile phase consisting of a mixture of methanol-0.05 M acetic acid (containing 8 mM sodium 1-heptanesulfanate) (65:35 v/v) with pH adjusted to 3.2 with triethylamine. The mobile phase was pumped at 0.80 mLmin(-1) flow rate and ACE was detected by diode-array detection at 240 nm. The retention times for ACE and internal standard (IS) were 4.574 and 8.236 min, respectively. A linear response (r = 0.9998) was observed in the range of 0.27-2.93 mu g mL(-1) in mobile phase. The limit of detection and limit of quantification were found as 0.07 and 0.23 mu g mL(-1) in the mobile phase. Validation parameters such as precision, accuracy, selectivity, reproducibility, and system suitability tests were also determined. The excipients did not interfere with the assay of ACE in tablet dosage forms. It is suggested that the proposed method can be used for routine quality control and dosage-form assay of ACE.
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.
A New Pyrimidine-Derived Ligand, N-Pyrimidine Oxalamic Acid, and Its Cu(Ii), Co(Ii), Mn(Ii), Ni(Ii), Zn(Ii), Cd(Ii), and Pd(Ii) Complexes: Synthesis, Characterization, Electrochemical Properties, and Biological Activity
(Taylor & Francis Ltd, 2010) Sonmez, Mehmet; Celebi, Metin; Levent, Abdulkadir; Berber, Ismet; Senturk, Zuehre
A new heterocyclic compound N-(5-benzoyl-2-oxo-4-phenyl-2H-pyrimidin-1-yl)-oxalamic acid has been synthesized from N-amino pyrimidine-2-one and oxalylchloride. Bis-chelate complexes of the ligand were prepared from acetate/chloride salts of Cu(II), Co(II), Mn(II), Ni(II), Zn(II), Cd(II), and Pd(II) in methanol. The structures of the ligand and its metal complexes were characterized by microanalyses, IR, AAS, NMR, API-ES, UV-Vis spectroscopy, magnetic susceptibility, and thermogravimetric analyses. An octahedral geometry has been suggested for all the complexes, except for Pd(II) complex, in which the metal center is square planar. Each ligand binds using C(2)=O, HN, and carboxylate. The cyclic voltammograms of the ligand and the complexes are also discussed. The new synthesized compounds were evaluated for antimicrobial activities against Gram-positive, Gram-negative bacteria and fungi using the microdilution procedure. The Cu(II) complex displayed selective and effective antibacterial activity against one Gram-positive spore-forming bacterium (Bacillus cereus ATCC 7064), two Gram-positive bacteria (Staphylococcus aureus ATCC 6538 and S. aureus ATCC 25923) at 40-80 mu g mL-1, but poor activity against Candida species. The Cu(II) complex might be a new antibacterial agent against Gram-positive bacteria.
Simple, Rapid, and Sensitive Electrochemical Determination of Antithyroid Drug Methimazole Using a Boron-Doped Diamond Electrode
(Springer, 2019) Seyidahmet, Safanur; Donmez, Fatih; Yardim, Yavuz; Senturk, Zuehre
This paper aims a rapid, cheap, simple and modification-free electroanalytical methodology using a boron-doped diamond electrode pretreated anodically for the determination of antithyroid drug methimazole in pharmaceutical samples. The drug was irreversibly oxidized which was a diffusion-controlled process. Using square wave voltammetry, a linear response was obtained for methimazole determination in Britton-Robinson buffer (pH 5.0) at +0.89V (vs. Ag/AgCl). Linearity was found between the oxidation peak currents and the concentration of methimazole from 0.5 to 25.0 mu g mL(-1) (4.38x10(-6)-2.19x10(-4)M) with a detection limit of 0.085 mu g mL(-1) (7.45x10(-7) M). The proposed method was applied for the determination of methimazole in commercial tablet samples.
Synthesis, Characterization, Cyclic Voltammetry, and Antimicrobial Properties of N-(5 Acid and Its Metal Complexes
(Taylor & Francis Ltd, 2010) Sonmez, Mehmet; Celebi, Metin; Levent, Abdulkadir; Berber, Ismet; Senturk, Zuehre
A new heterocyclic compound, N-(5-benzoyl-2-oxo-4-phenyl-2H-pyrimidin-1-yl)-malonamic acid, was synthesized from N-aminopyrimidine-2-one and malonyldichloride. Bis-chelate complexes of the ligand were prepared from acetate/chloride salts of Cu(II), Co(II), Ni(II), Mn(II), Zn(II), Cd(II), Fe(III), Cr(III), and Ru(III) in methanol. The structures of the ligand and its metal complexes were characterized by microanalyses, IR, NMR, API-ES, UV-Vis spectroscopy, magnetic susceptibility, and conductometric analyses. Octahedral geometry was suggested for all the complexes, in which the metal center coordinates to ONO donors of the ligand. Each ligand binds the metal using C=O, HN, and carboxylate. The cyclic voltammograms of the ligand and the complexes were also discussed. The compounds were evaluated for their antimicrobial activities against Gram-positive and Gram-negative bacteria, and fungi using microdilution procedure. The antimicrobial studies showed that Cu(II), Fe(III), and Ru(III) complexes exhibited good antibacterial activity against Gram-positive bacteria with minimum inhibitory concentrations between 20 and 80 mu g mL-1. However, the ligand and the complexes possess weak efficacy against Gram-negative bacterium and Candida strains. As a result, we suggest that these complexes containing pyrimidine might be a new group of antibacterial agents against Gram-positive bacteria.
Voltammetric Method for the Simultaneous Determination of Melatonin and Pyridoxine in Dietary Supplements Using a Cathodically Pretreated Boron-Doped Diamond Electrode
(Wiley-v C H verlag Gmbh, 2017) Alpar, Nurcan; Pinar, Pinar Talay; Yardim, Yavuz; Senturk, Zuehre
The simultaneous voltammetric determination of melatonin (MT) and pyridoxine (PY) has been carried out at a cathodically pretreated boron-doped diamond electrode. By using cyclic voltammetry, a separation of the oxidation peak potentials of both compounds present in mixture was about 0.47 V in Britton-Robinson buffer, pH 2. The results obtained by square-wave voltammetry allowed a method to be developed for determination of MT and PY simultaneously in the ranges 1-100 mu g mL(-1) (4.3x10(-6)-4.3x10(-4) mol L-1) and 10-175 mu g mL(-1) (4.9x10(-5)-8.5x10(-4) mol L-1), with detection limits of 0.14 mu g mL(-1) (6.0x10(-7) mol L-1) and 1.35 mu g mL(-1) (6.6x10(-6) mol L-1), respectively. The proposed method was successfully to the dietary supplements samples containing these compounds for health-caring purposes.