Yazar "Denizhan, Nuray" seçeneğine göre listele

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  • [ X ]
    Öğe
    Application of a cyclic renewable silver amalgam liquid film electrode (R-AgLAFE) to study the electroreduction processes of Bi(III) ions in the presence of cysteine
    (2022) Nosal-Wierci?ska, Agnieszka; Martyna, Marlena; Wi?niewska, Ma?gorzata; Yılmaz, Selehattin; Denizhan, Nuray
    The cyclically refreshable liquid silver amalgam film silver-based electrode (R-AgLAFE) to study electrode processes under the “cap-pair” conditions were used. The effects of cysteine on the kinetics and the mechanism of Bi(III) electroreduction in chlorates(VII) have been studied. The methodology of the study is based on electrochemical methods: DC polarography, square wave voltammetric (SWV), and cyclic voltammetric (CV). The magnitude of the catalytic effect is related to the formation of the $Bi(III)-Hg(SR)_2$ active complexes mediating electron transfer equilibrium. This reaction controls the total rate of the process.
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    Öğe
    Electrochemical and liquid chromatographic analysis of triamcinolone acetonide in pharmaceutical formulations
    (2022) Denizhan, Nuray; Yılmaz, Selehattin; Sağlıkoğlu, Gülşen; Kılınc, Emrah; Yengın, Çiğdem; Der, Fatma Gülay
    Electrochemical reduction of triamcinolone acetonide on pencil graphite electrode surface was firstly investigated by cyclic voltammetry (CV). The dependence of cathodic peak current and peak potential on different pH medium and scan rate were investigated. The adsorption controlled nature of the peak was achieved. During pH optimization, 0.067 M Phosphate (pH 4.50 to pH 7.50), 0.2 M Acetate (pH 3.50 to 5.50) and 0.04 M Britton Robinson (BR; pH 2.00 to 12.00) buffers were employed as supporting electrolytes. Scan rate optimization was investigated in the range 25-1000 mVs-1 (vs. Ag/AgCl). Maximum peak current was observed in the 0.04 M BR buffer (pH 3.50). Peak current increases and shifts to more cathodic values with the increasing scan rate. Curve of logarithm of peak current (log I) versus logarithm of scan rate (log v) showed linear regression with the equation log(Ip/?A) = 0.8395 log(v/mVs-1)-0.8386 and correlation coefficient (R2: 0.9761). This indicated that slope of the logv-logI curve is close to 1.0 and the cathodic electrode reaction was adsorption controlled, as desirable. The linear range was 1×10-7-5×10-5 M, sensitivity was 1,3347 µA M-1, Limit of detection (LOD) and Limit of quantification (LOQ) were 3.18×10-8 M and 1.00×10-7 M, respectively. HPLC-PDA analysis were performed with H2O:MeOH (28:72, v/v) as mobile phases A and B at a flow rate of 1mL/min at 242nm. Method validation studies were conducted in accordance with ICH Q2(R1) guideline and corresponding results were summarized in tables. HPLC-PDA method displayed linearity in 0.1-50µg/mL (2.3×10-7-1.15×10-4 M) concentration range with LOD and LOQ values as 3.992×10-8 and 1.29×10-7M, respectively.
  • Küçük Resim
    Öğe
    Fabrication of PAMP/Au and GO/PAMP/Au nanosensors for electrochemical detection of paracetamol in pharmaceutical preparations
    (Springer, 2021) Bilici, Ali; Denizhan, Nuray; Emre, Deniz; Yılmaz, Selehattin; Soylukan, Caner; Algi, Fatih
    This paper reports on the modification of Pencil Graphite Electrode (PGE) surface with the poly(2-amino-4-methylphenol)/gold (PAMP/Au) and graphene oxide/poly(2-amino-4-methylphenol)/gold (GO/PAMP/Au) nanocomposites, in two steps. The first step is based on the one-pot preparation of composites by template-free chemical oxidation process. In the second step, composites are deposited at PGE surface by electro-oxidation process. Both nanocomposites and modified PGE surfaces are characterized by X-Ray Diffraction method (XRD), Scanning Electron Microscopy (SEM), EDAX, and CV analyses. The electrochemical performances of modified electrodes (abbreviated as PAMP/Au-PGE and GO/PAMP/Au-PGE) were investigated. The limit of detection values for PGE, PAMP/Au-PGE, and GO/PAMP/Au-PGE were found to be 2.74 × 10–6, 5.29 × 10–7, and 2.91 × 10–8 mol/dm3, respectively. The limit of quantification values were determined as 9.14 × 10–6, 1.76 × 10–6, and 9.69 × 10–8 mol/dm3 for PGE, PAMP/Au-PGE, and GO/PAMP/Au-PGE, respectively.
  • Küçük Resim
    Öğe
    Graphene quantum dots-polyfluorene hybrid nanobiosensor for mitomycin C-DNA interaction sensing
    (Elsevier Ltd, 2024) Emre, Deniz; Denizhan, Nuray; Özkan-Arıksoysal, Dilsat; Bilici, Ali; Sonkaya, Ömer; Algı, Fatih; Yılmaz, Selehattin
    A novel graphene quantum dots (GQD) / polyfluorene (PF) nanocomposite was deposited on the disposable pencil tip graphite electrode (PGE) and proven to be an efficient nanosensor for analysis of the electrochemical interaction between the antitumor compound mitomycin C (MC) with double stranded DNA (ds-DNA). This modified electrode (GQD@PF-PGE) was prepared in four steps: hydrothermal, chemical oxidation, ultrasonication and electro-oxidation processes. GQD, PF, GQD@PF and GQD@PF-PGE have been characterized by different analytical techniques such as SEM, TEM, XRD, FTIR, UV–Vis, EIS. Compared to bare PGE, GQD@PF modified PGE performed approximately 56 times more sensitive analysis when evaluating the guanine oxidation signals measured by DPV. CV and EIS measurements also showed that GQD@PF-PGE possesses a fast electron transfer as compared to bare electrode and exhibit a remarkable electrocatalytic activity towards both guanine and MC electrooxidation. Comprehensive optimization studies have also been carried out for the developed new nanobiosensor.
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    Öğe
    Triamsınolon asetonidin elektrokimyasal davranışı ve ilaç formlarından HPLC ile analizi
    (Çanakkale Onsekiz Mart Üniversitesi, 2019) Denizhan, Nuray; Yılmaz, Selehattin
    Triamsinolon Asetonid'in (TA) voltametrik tekniklerle elektrokimyasal davranışı, Yüsek Performanslı Sıvı Kromatografisi (HPLC) tekniğiyle ise ilaç formlarındaki miktarı belirlenmiştir. Elektrokimyasal deneyler kalem ucu grafit elektrotta (KUGE) 0.50-12.00 pH arasındaki çeşitli tampon çözeltiler kullanarak Döngüsel Voltametri (CV) ve Diferensiyel PulsVoltametrisi (DPV) metodlarıyla gerçekleştirilmiştir. Kromatografik deneyler ise C18 analitik kolon ile 25oC'de ve 254 nm'de gerçekleştirilmiştir. TA'nın çalışma ortamını belirlemek için farklı destek elektrolitlerde pH'ın pik potansiyeline ve pik akımına etkisi incelenmiştir. Yüksek akımın ve en iyi pikin gözlendiği Britton-Robinson tampon çözeltisi (pH 3.50) seçilmiştir. CV ölçümlerinden elde edilen tarama hızının karekökü-akım değerleri ve log v-logi grafiklerinden, akımın adsorpsiyon kontrollü olduğu tespit edilmiştir. Gercek ilaç numunelerinde TA'nın miktarı HPLC tekniği ile belirlenmiştir. Bu amaçla TA' nın 2,3x10-7 – 1,15x10-4 derişim aralığında HPLC yöntemi ile lineer bir kalibrasyon doğrusu oluşturulmuştur. Bu kalibrasyon grafiği kullanılarak belirme sınırı ve kantitatif tayin sınırı sırasıyla 3,92x10-8 ve 1,29x10-7 olarak bulunmuştur. Daha sonra TA'nın ilaç formlarındaki miktarı belirlenmiştir. Gerçek ilaç numunlerine uygulanan HPLC metodunun validasyonu da yapılmıştır.