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    Application of a pencil graphite electrode for voltammetric simultaneous determination of ascorbic acid, norepinephrine, and uric acid in real samples
    (TÜBİTAK, 2018-04-27) Levent, Abdulkadir; Önal, Günay
    A pencil graphite electrode (PGE) was used for the simultaneous detection of ascorbic acid (AA), norepinephrine (NE), and uric acid (UA) by differential pulse voltammetry and cyclic voltammetry. The anodic peaks of AA, NE, and UA in their mixture can be well separated in 0.1 M Britton–Robinson buffer solution at pH 4.0. The effects of various experimental parameters such as pH, scan rate, and voltammetric parameters on the voltammetric response of these compounds were investigated. Under optimum conditions, linear calibration graphs were obtained from the AA, NE, and UA concentration ranges, which were 100–800 nM, 20–170 nM, and 40–175 nM, respectively. The detection limits for AA, NE, and UA were 27 nM, 4 nM, and 10 nM in the form of a mixture at the PGE. This electrode shows great analytical performance characteristics, corresponding repeatability and recovery for the simultaneous determination of these compounds. PGE, which was used for the first time in this method, has been successfully applied for the assay of UA in human urine samples with the aim of determining AA and NE in pharmaceutical drugs.
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    Application of bismuth film electrode in determination of Loratadine by cathodic stripping voltammetry in the presence of cationic surfactant
    (ICNTC, 2020) Önal, Günay; Altunkaynak, Yalçın; Levent, Abdulkadir
    Loratadine, histamine - H1 antihistamine receptors it is being used for many years in the treatment of an allergic condition illustrating the effects on[1]. When the literature is reviewed, there are limited number of studies on Loratadine based on electrochemistry [2-5]. Stripping voltammetry is a very sensitive and selective method for determining drugs and organic / inorganic substances in biological fluids. The electrochemical behavior of Loratadine with BiFE in different supporting electrolyte and pH values, and its performance characteristics in electroanalytical determinations were investigated by cyclic voltammetry and linear sweep cathodic stripping voltammetry (LS-CSV) methods. LS-CSV measurements on the BiFE surface of 6.5x10-4 M Loratadine in 0.04 M BR buffer (pH 7.0) and 4 mM cationic surfactant (CTAB) were taken between 0.0 V and -2.0 V. Loratadine gave a voltammetric response about at -1.486 V. The limit of detection was found LOD = 1.2x10-7 M* at the BIFE surface at liner concentration range [1.305x10-6 M – 14.3x10-6 M, r = 0,998* (n = 11)]. This voltammetric method, developed under optimum conditions, has been successfully applied to pharmaceutical formulations of Loratadin as fast, easy to apply, sensitive and environmentally friendly.
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    Archaeometric review of the tile decorations in Hasankeyf Zeynel Bey Tomb with P-EDXRF
    (Batman Üniversitesi, 2022-12-31) Turan, Emine; Levent, Abdulkadir
    Tile is known as a handicraft based on the production of items such as vases, jugs and pots by shaping the soil after cooking. It is defined as the covering material processed with colorful décor and motifs used in the decoration of items such as tiles, ceramics, porcelain plates and china making in the goods processed with the help of this material. In this study, 7 Light Blue Glaze, 7 Navy Blue Glaze and 8 Unglazed Tile belonging to Zeynel Bey Tomb, a total of 22 tiles were analyzed in Hasankeyf Cultural Park where the tomb was moved with P-EDXRF. As a result; The chemical contents of the 22 samples we examined on site were determined and compared with the previous studies. It was determined that the results obtained were compatible.
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    Batman Üniversiteli kadın akademisyenin bilimsel profili
    (Batman Üniversitesi, 2017) Kaçmaz Levent, Esra; Levent, Abdulkadir
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    Bor katkılı elmas elektrot ile naftalin’in voltametrik davranışı: Kare dalga anodik sıyırma voltametrisi ile miktar tayini
    (Süleyman Demirel Üniversitesi, 2017-04-28) Levent, Abdulkadir
    Bu çalışmada, Naftalin bor katkılı elmas elektrot yüzeyindeki elektrokimyasal özellikleri, değişik çözelti ortamları ve geniş bir pH aralığında incelenmiştir. İlk olarak çalışma elektrotun performansını etkileyen değişkenler (destek elektrolitinin seçimi, elektrot temizleme yöntemi, iyon şiddeti ve pH, biriktirme/ölçüm çözeltisinin bileşimi, biriktirme gerilimi/süresi, voltametrik dalga formu değişkenleri); voltametri ve/ya da sıyırma voltametrisi teknikleri kullanılarak ayrıntılı olarak araştırılmıştır. Daha sonra önerilen yöntemlerin elde edilen optimum koşullarda Naftalin için doğrusallık (0.9-4.5 µM), saptama sınırı (LOD; 0.225 µM) ve kesinlik (% BSS 2.26) açısından validasyonu gerçekleştirilmiştir. Geliştirilen KD-ASV yöntemi, çeşme suyunda naftalinin analizi için standart katma yöntemi kullanılarak başarılı bir şekilde uygulanmıştır.
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    The changes in the serum, liver, kidney protein and genomic DNA profiles in rats treated with 7,12-Dimethylbenz(A) anthracene and Plantago major L.
    (RJPBCS, 2014-01) Berber, İsmet; Ekin, Suat; Levent, Abdulkadir; Oto, Gökhan;
    In the study, the changes in the serum, liver, kidney protein and genomic DNA profiles in Wistar albino rats administrated to 7,12-dimethylbenz(a)anthracene (DMBA) and Plantagomajor L. were investigated. SDS-PAGE profiling of the serum proteins showed that the levels of two proteins molecular weighing 140.8 kDa and 46.8 kDa were significantly lower on the 0th day of treatment than on the 60th day of application in the groups. Furthermore, two proteins (34.5 and 22.3 kDa) were solely present in DMBA-treated liver cell lysates. On the contrary, the kidney protein profiles did not show significant banding variations in groups. Genomic DNA analysis also confirmed that DNA extracted from liver and kidney cells did not fragment in any of the groups after the 60th study day. The proteins 34.5 and 22.3 kDa in liver cell lysates at the 60th day in DMBA-treated group could be extra-prognostic indicators for severe DMBA toxicity.
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    Determination of 7,12-dimethylbenz[a]anthracene in orally treated rats by high-performance liquid chromatography and transfer stripping voltammetry
    (Bentham, 2012-06) Yardım, Yavuz; Levent, Abdulkadir; Ekin, Suat; Keskin, Ertuğrul; Oto, Gökhan; Şentürk, Zühre
    A number of polycyclic aromatic hydrocarbons (PAHs) have been shown to be toxicants, and induce carcinogenic and immunotoxic effects. As a model PAH agent, 7,12-dimethylbenz[a]anthracene (DMBA) was the strongest one tested in terms of its biological activities and biotransformation. A new and simple high-performance liquid chromatographic (HPLC) method with diode-array detection at 290 nm was developed and validated for monitoring of DMBA in different matrices (serum, liver and kidney) of rats orally treated with DMBA. Furthermore, the applicability of adsorptive transfer stripping voltammetry (AdTSV) on the pencil-lead graphite electrode to these samples was illustrated using our previously reported data for bulk aqueous solutions of DMBA. HPLC and AdTSV methods, which were compatible with each other, allowed DMBA to be detected down to the levels of 3.82x10-9 M (0.98 ppb) and 6.73x10-9 M (1.73 ppb), respectively. Olive oil solutions of DMBA in dose 50 mg/kg were orally administered. 60 days after a single dose of DMBA, its concentrations in these biological samples from rats were measured by means of both methods. Because of rapid biotransformation, DMBA could not be detected in serum. Only low levels of the compounds were deposited unchanged in kidney whereas its levels were considerably higher in liver. These methods were also applied to the assay whether there is an influence of the intake of aqueous extracts of Hypericum Perforatum L. plant on the parent DMBA levels accumulated in rat tissues.
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    Determination of trace metal and mineral levels in the tobacco and cigarette samples using by FASS
    (Chemical Society of Pakistan, 2013-04) Levent, Abdulkadir; Yardım, Yavuz; Demir, Cengiz
    Cigarettes and tobacco products are consumed in large amounts by human beings in the world. Also, tobacco is one of the most important agricultural products in Turkey. The accumulation of heavy metals in tobacco leaves in accordance with a possible risk of transferring them to people by smoke is well known. This study was carried out to estimate trace metal and mineral levels in tobacco and cigarettes from Eastern and South-eastern Anatolia, Turkey. The analysis was done by flame atomic absorption spectrometry using dry ashing or wet digestion. Results obtained are in agreement with data reported in the literature.
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    The effect of Plantago major Linnaeus on serum total sialic acid, lipid-bound sialic acid, some trace elements and minerals after administration of 7,12-dimethylbenz(a)anthracene in rats
    (SAGE, 2012-04) Oto, Gökhan; Ekin, Suat; Özdemir, Hülya; Levent, Abdulkadir; Berber, İsmet
    The present study was designed to evaluate the effect of Plantago major Linnaeus (PM) extract on serum total sialic acid (TSA), lipid-bound sialic acid (LSA), some trace elements (copper (Cu), zinc (Zn) and iron) and mineral levels (magnesium, calcium and sodium) in Wistar albino rat administrated 7,12-dimethylbenz(a)anthracene (DMBA). Rats were divided into three equal groups (n = 6). Group I comprised the control group, group II was treated with DMBA (100 mg/kg, single dose) and group III was treated with DMBA (100 mg/kg single dose) and aqueous extract of PM 100 mg/kg/day for 60 days. After 60 days, statistical analyses showed that TSA and LSA levels in DMBA and DMBA + PM groups were significantly higher compared to the control group (TSA: p < 0.01, p < 0.05; LSA: p < 0.05, p < 0.05, respectively). Serum Zn levels were decreased in subjects treated with DMBA (p < 0.01) and DMBA + PM (p < 0.05) compared to the control group values. Serum Cu levels were increased in DMBA group and PM-treated group compared to the control group values. The results of this investigation showed that the levels of TSA and LSA changed significantly, which are sensitive markers for detecting the toxic effects of DMBA. On the other hand, observed decline in Zn levels in rats from DMBA + PM group might be due to decreased generation of free radicals and oxidative stress. Results from this study suggest that PM may be partially effective in preventing carcinogenesis initiated by environmental carcinogen DMBA.
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    Electroanalytical determination of progesterone hormone using borondoped diamond electrode
    (ICNTC, 2020) Levent, Abdulkadir; Uçar, Muhlis
    Progesterone 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.
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    Electroanalytical investigation of antineoplastic drug vinorelbine at pencil graphite electrode in surfactant media
    (Turkish Chemical Society, 2019) Önal, Günay; Levent, Abdulkadir; Şentürk, Zühre
    Vinorelbine (sold under the brand name Navelbine), one of the semisynthetic derivatives of Vinca alkaloids, has been widely used either alone or in combination with other drugs in the tre- atment of leukemia, lymphoma, advanced testicular cancer and Kaposi's sarcoma. From the electrochemical point of view, only one study that was quite old has been reported on its voltammetric characteris- tics so far (Brett et al.). Keeping the above knowledge in mind, in the present study, a novel application of single-use pencil graphite (PG) electrode is introduced for the determination of Vinorelbine. The electrochemical oxidation of this compound was first investigated by cyclic voltammetry in aqueous solutions. Special attention was given to the use of adsorptive stripping vol- tammetry at a surface of PG electrode and glassy carbon (GC) one (for comparison purpose) in aqueous solutions over the pH range of 2.0-12.0 both without and with the addition of different charged surfactants. The sensitivity of the stripping voltammet- ric measurements was significantly improved when the anionic (sodium dodecylsulfate, SDS) and cationic (tetra-n-butylammo- nium bromide, TBAB) surfactants were present in the Vinorelbi- ne-containing electrolyte solution at pH 2.0-4.0 and pH 9.0-10.0, respectively, by using PG electrode. Using square-wave stripping mode, Vinorelbine yielded a well-defined voltammetric response in Britton-Robinson buffer pH 10.0 containing 3×10−3 M TBAB at +0.75 V (vs. Ag/AgCl) (after 120 s accumulation at +0.0 V). The process could be used to determine this compound in the concentration range of 2.3×10−8 – 5.8×10−6 M, with a detection limit of 7.5×10−9 M (base-5.8 ng mL1−). The proposed method was successfully applied to pharmaceutical formulations and the spiked human urine samples.
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    Electrochemical determination of melatonin hormone using a boron-doped diamond electrode
    (Elsevier, 2012-01) Levent, Abdulkadir
    In 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.
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    Electrochemical oxidation of vildagliptin on pencil graphite electrode: Extremely sensitive determination in drugs and human urine with square wave voltammetry
    (ICNTC, 2020) Altunkaynak, Yalçın; Yavuz, Ömer; Levent, Abdulkadir
    Vildagliptin (VLDG), one of the antidiabetic agents, is a dipeptidyl peptidase 4 inhibitor. It is a drug developed for oral administration[1]. In the literature, there is only one study in which electrochemical methods were used for the analysis of Vildagliptin in biological fluid and drug forms[2]. In this study, the electrochemical properties of VLDG, which is one of the drugs used as an antidiabetic agent, were determined by using pencil graphite electrode in phosphate buffer solution (PBS/pH 9.0). The irreversible and diffusion controlled adsorption oxidation peak was measured by cyclic voltammetry at approximately +1.13 V for this compound. Using square wave stripping voltammetry, the current showed a linear correlation in PBS buffer at pH 9.0, with a concentration range of 2.94 to 49.98 µM. At a concentration of 2.94 µM (n=9), the limit of detection of 8.20 nM (2.48 ng mL-1 ) and a relative standard deviation of 2.95 % were calculated. This method was successfully applied for VLDG analysis without any separation in pharmaceutical preparations and urine samples
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    Electrochemical performance of boron-doped diamond electrode in surfactant-containing media for ambroxol determination
    (Elsevier, 2014-07-17) Levent, Abdulkadir; Yardım, Yavuz; Şentürk, Zühre
    A 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.
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    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, Zühre
    The 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.
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    Fluorescence properties and electrochemical behavior of some schiff bases derived from n-aminopyrimidine
    (Springer Nature, 2014-03) Gülcan, Mehmet; Doğrul, Ümit; Öztürk Ürüt, Gülsiye; Levent, Abdulkadir; Akbaş, Esvet
    A series of Schiff bases (L 1, L 2 and L 3 ) were prepared by refluxing aromatic aldehydes with N-Aminopyrimidine derivatives in methanol and ethanol. The structures of synthesized compounds were characterized by FTIR, 1H NMR, 13C NMR and microanalysis. The electrochemical behaviors of the Schiff base ligands were also discussed. Moreover, the evaluation of absorption and emission properties of the structures were carried out in five different solvents. The products show visible absorption maxima in the range of 304-576 nm, and emission maxima from 636 to 736 nm in all solvents tested.
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    Graphene/Nafion composite film modified glassy carbon electrode for simultaneous determination of paracetamol, aspirin and caffeine in pharmaceutical formulations
    (ScienceDirect, 2016-05-16) Yiğit, Aydın; Yardım, Yavuz; Çelebi, Metin; Levent, Abdulkadir; Şentürk, Zühre
    A graphene-Nafion compositefilm was fabricated on the glassy carbon electrode (GR-NF/GCE), and usedfor simultaneous determination of paracetamol (PAR), aspirin (ASA) and caffeine (CAF). The electro-chemical behaviors of PAR, ASA and CAF were investigated by cyclic voltammetry and square-waveadsorptive anodic stripping voltammetry. By using stripping one for simultaneous determination of PAR,ASA and CAF, their electrochemical oxidation peaks appeared atþ0.64, 1.04 and 1.44 V, and good linearcurrent responses were obtained with the detection limits of 18 ng mL 1(1.2 10 9M), 11.7 ng mL 1(6.5 10 8M) and 7.3 ng mL 1(3.8 10 8M), respectively. Finally, the proposed electrochemical sensorwas successfully applied for quantifying PAR, ASA and CAF in commercial tablet formulations.
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    Katyonik sürfaktan madde varlığında bizmut film elektrot kullanarak desloratadinin elektrokimyasal olarak indirgenmesi: Lineer taramalı sıyırma voltametrisi ile ilaç ve idrar numunelerine uygulanması
    (BioTechBioChem, 2020) Altunkaynak, Yalçın; Önal, Günay; Levent, Abdulkadir
    Histamin, mide salgısının güçlü bir uyarıcısı olan biyolojik bir amin olup etkili bir nörotransmitterdir[1]. Literatürde biyolojik sıvı ve ilaç şekillerinde desloratadin (DESL) analizi için önerilen elektrokimyasal yöntemlerin temel alındığı teknikleri kullanıldığı birkaç çalışma vardır[2-6]. Bu çalışmada, ikinci nesil antihistaminikler grubundan olan DESL’nin elektrokimyasal özellikleri, Bizmut Film eleketrot (BİFE) kullanılarak sulu ve sulu/yüzey aktif madde çözeltilerinde gerçekleştirildi. Bu bileşik dönüşümlü voltametri ile yaklaşık -1.65 V da tersinmez ve adsorpsiyon kontrollü bir indirgenme piki göstermiştir. Katyonik yüzey aktif madde (setiltrimetilamonyum bromür, CTAB) ilavesinin desloratadinin indirgeme akım sinyalini arttırdığı, anyonik (sodyum dodesilsülfat, SDS) ve iyonik olmayan (Tween 80) yüzey aktif maddelerinin ise ters etki sergilediği bulundu. Linear taramalı adsorptif sıyırma voltametrisi kullanılarak akım, 5 mM CTAB içeren BrittonRobinson tamponunda, pH 8.0'de 0.1 ile 4 µM derişim aralığında doğrusal bir bağıntı göstermiştir(Şekil 1). Şekil 1. 0.1- 4 μM derişim aralığında BR tampon( pH 8.0 / 5 mM CTAB içeren) ortamında lineer taramalı sıyırma voltametri eğrileri Bu çalışmada geliştirilen yöntem, farmasötik preparatlarda ve idrar örneklerinde herhangi bir ayırma işlemi yapılmadan DESL analizi için başarılı bir şekilde uygulanmıştır.