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Öğe Silica gel-immobilized 5-aminoisophthalohydrazide: A novel sorbent for solid phase extraction of Cu, Zn and Pb from natural water samples(Wiley Online Library, 2020-03-11) Aydın, Funda; Çakmak, Reşit; Levent, Abdulkadir; Soylak, MustafaA novel silica sorbent, silica gel‐immobilized 5‐aminoisophthalohydrazide (SiO2‐APH), was prepared by the condensation of 3‐chloropropyl‐functionalized silica gel with 5‐aminoisophthalohydrazide (APH) derived from dimethyl 5‐aminoisophthalate as a starting material and used for separation and preconcentration of Cu, Zn, and Pb metals in water samples using Flame Atomic Absorption Spectrometry (FAAS). The characterization of the new sorbent was carried out by Elemental Analysis, Thermogravimetric Analysis (TGA) and Fourier Transform Infrared Spectroscopy (FTIR). Important analytical parameters including as pH, amount of sorbent, type and amount of eluting solvent, sample volume, vortex and ultrasonic bath time, matrix ions that effect the developed SiO2‐APH‐solid phase extraction (SPE) method were investigated and optimum parameters were detected. Recoveries of examined metals were obtained as 98% for Cu and Pb and 101% for Zn. The relative standard deviation (RSD, n = 8) of Cu, Zn and Pb metals were 3.2, 2.8 and 1.6%, respectively. Limit of detections (LODs) (n = 10) were found as 2.7 μg L−1 for Cu, 7.4 μg L−1 for Zn and 3.5 μg L−1 for Pb μg L−1. The accuracy of the new method was assessed by analyzing of TMDA‐51.4 and TMDA‐70.2 certified reference materials. The results obtained for metals were in a good agreement with certified values. Addition/recovery test was applied to the real well, river, dam and stream water samples to check the accuracy of the method. The results showed that the developed SiO2‐APH‐SPE method can be effectively used as an alternative method for determination of Cu, Zn, and Pb metals in water samples.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 Synthesis, characterization and experimental, theoretical, electrochemical, antioxidant and antibacterial study of a new Schiff base and its complexes(Elsevier, 2014-09-15) Baykara, Hacı; İlhan, Salih; Levent, Abdulkadir; Seyitoğlu, Mehmet Salih; Özdemir, Sadin; Okumuş, Veysi; Öztomsuk, Abdussamet; Cornejo, MauricioA new Schiff base ligand was synthesized by reaction of salicylaldehyde with 1,6-bis(4-chloro-2-aminophenoxy)hexane. Then the Schiff base complexes were synthesized by metal salts and the Schiff base. The metal to ligand ratio of metal complexes was found to be 1:1. The Cu(II) complex is proposed to be square planar and the Co(II), Ni(II), Mn(II) and Zn(II) complexes are proposed to be tetrahedral geometry. The Ti(III) and V(III) complexes are proposed to be a capped octahedron in which a seventh ligand has been added to triangular face. The complexes are non-electrolytes as shown by their molar conductivities (ΛM). The structure of metal complexes is proposed from elemental analysis, FT-IR, UV–vis, magnetic susceptibility measurements, molar conductivity measurements, Mass Spectra and thermal gravimetric analysis. In addition antimicrobial and antioxidant studies, cyclic voltammetry of the complexes, theoretical 1H NMR and HOMO–LUMO energy calculations of the new di-functional ligand were done.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 Preparation, spectral studies, theoretical, electrochemical and antibacterial investigation of a new Schiff base and its some metal complexes(Elsevier, 2014-10-05) İlhan, Salih; Baykara, Hacı; Seyitoğlu, Mehmet Salih; Levent, Abdulkadir; Özdemir, Sadin; Dündar, Abdurrahman; Öztomsuk, Abdussamet; Cornejo, MauricioA new Schiff base ligand, 1,6-Bis(2-(5-bromo-2-hydroxybenzylideneamino)-4-chlorophenoxy)hexane was synthesized. Some Schiff metal complexes of the new Schiff base were prepared by the reaction of some metal salts and the Schiff base. The complexes are non-electrolytes as shown by their molar conductivities (ΛM). The structures of metal complexes are proposed from elemental analysis, FT-IR, UV–vis, magnetic susceptibility measurements, molar conductivity measurements, mass spectra and thermal gravimetric analysis. In addition theoretical 1H NMR, HOMO–LUMO studies of the ligand; antimicrobial and cyclic voltammetric studies of the compounds were also carried out. In this study antioxidant and antibacterial activities of the compounds were examined via in vitro methods.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 Synthesis and characterization of 1,2-bis(2-(5-bromo-2-hydroxybenzilidenamino)-4-chlorophenoxy)ethane and its metal complexes: An experimental, theoretical, electrochemical, antioxidant and antibacterial study(Elsevier, 2014-01-24) İlhan, Salih; Baykara, Hacı; Öztomsuk, Abdussamet; Levent, Abdulkadir; Seyitoğlu, Mehmet Salih; Özdemir, SadinA new Schiff base ligand was synthesized by reaction of 5-bromosalicylaldehyde with 1,2-bis(4-chloro-2-aminophenoxy)ethane. Then the Schiff base complexes were synthesized by the reaction of metal salts and the novel Schiff base. The molar conductivity properties of the complexes were studied and found out that the complexes are nonelectrolytes. The structures of the ligand and its metal complexes were characterized by elemental analysis, FT-IR, UV–VIS, magnetic susceptibility measurements, molar conductivity measurements, and thermal gravimetric analysis. In addition antioxidant, theoretical NMR studies and cyclic voltammetry of the complexes were done. Two methods namely metal chelating activity and diphenylpicrylhydrazyl (DPPH) radical scavenging method were used to determine the antioxidant activity, and antibacterial properties of the compounds were also studied.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.Öğe Synthesis, theoretical calculation, electrochemistry and total antioxidant capacity of 5-benzoyl-6-phenyl-4-(4-methoxyphenyl)-1,2,3,4-tetrahydro-2-thioxopyrimidine and derivatives(ScienceDirect, 2017-02-07) Ergan, Erdem; Akbaş, Esvet; Levent, Abdulkadir; Şahin, Ertan; Konuş, Metin; Seferoğlu, Nurgül5-Benzoyl-6-phenyl-4-(4-mehtoxyphenyl)-1,2,3,4-tetrahydro-2-thioxopyrimidine (1) have been pre-paredviaBiginelli cyclocondensation reaction in acetic acid under reflux condition in good yield. Thestructure of1was determined by using spectroscopic techniques like1H/13C NMR and elemental ana-lyses. And also their molecular characterizations of compounds were analyzed by X-ray crystal analysis. Aseries of novel pyrimidine derivatives were obtained by reaction compound1with various reactive. Allsynthesized pyrimidine derivatives and related keto and enol tautomeric forms have been optimizedgeometrically with DFT in Gaussian at the B3LYP/6-31þG (d, p) level in order to obtain informationabout the 3D geometries and electronic structures. The results showed that the keto tautomer is morestable than enol tautomer. However, the non-linear optical (NLO) properties were evaluated theoreti-cally. The electrochemical properties of the novel compounds were investigated by CV and DPV. Inaddition, the total antioxidant capacities of all new synthesized compounds were measured in vitro byABTS assay.
