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  • Küçük Resim
    Öğe
    An application of a disposable electrode for the sensitive, selective, and cost-effective voltammetric determination of antiparkinsonism drug entacapone based on both its oxidation and reduction
    (Springer, 2025) Vural, Kader; Giray Dilgin, Didem; Dilgin, Yusuf
    Entacapone (ETC) is an important drug active ingredient frequently used together with levodopa (LD) and carbidopa (CD) in the treatment of Parkinson's disease. This study describes a simple, selective, sensitive, and cost-effective voltammetric determination of ETC based on both its oxidation and reduction at a disposable graphite pencil electrode (GPE). The electrochemical oxidation and reduction of ETC were investigated by recording cyclic voltammograms (CVs) of ETC based on the pH of the supporting electrolyte at a fixed scan rate and the scan rate at the supporting electrolyte of 0.10 M H2SO4. The analytical performance studies were carried out by recording differential pulse voltammograms (DPVs) under optimized conditions and by considering both the anodic and the irreversible cathodic peak at - 130 mV. DPV results show that the disposable and unmodified GPEs have linear ranges of 2.5-1500 and 2.5-1000 nM with detection limits of 0.79 and 0.69 nM for reduction and oxidation, respectively. The effects of some potential interferants were investigated, and no significant interference among the studied compounds, such as CD, LD, and dopamine (DA), was observed. The DP voltammetric procedure using disposable GPE was applied to determine ETC in pharmaceutical tablets using antiparkinsonism treatment including triple compounds (ETC, CD, and LD) and an artificial urine sample. Acceptable results for both samples show that ETC can be cost-effectively determined with high accuracy, sensitivity, and precision in real samples.
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    Öğe
    Bir antiparkinson ilaç etken maddesi olan Entakapon'un kalem grafit elektrotla elektrokimyasal tayini
    (Çanakkale Onsekiz Mart Üniversitesi, 2024) Vural, Kader; Dilgin, Didem Giray
    Bu tez çalışmasının amacı, kolay temin edilebilen, tek kullanımlık, elektrokimyasal olarak oldukça reaktif ve çok avantajlı kalem grafit elektroda (PGE) dayalı olarak entakapon'un (ETK) seçici ve oldukça hassas tayinini gerçekleştirmektir. ETK tayini için çeşitli modifiye elektrotlar rapor edilmiş olmasına rağmen, PGE hem yükseltgenmeye hem de indirgenmeye dayalı ETK tayini için kullanılmamıştır. Bu nedenle, ilk olarak, ETK'nın elektrokimyasal davranışı, destek elektrolitin pH'sına ve tarama hızlarına bağlı olarak ETK'nın döngüsel voltammogramları kaydedilerek incelenmiştir. Sonuçlar, PGE'de ETK'nın hem yükseltgenmesinin hem de indirgenmesinin difüzyon kontrollü bir süreçle gerçekleştiğini göstermiştir, çünkü her iki pik akımı da tarama hızının kareköküne bağlı olarak doğrusal bir şekilde artmıştır. Analitik performans çalışmaları, optimize edilmiş koşullar altında 0,1 M H2SO4 içinde ETK'nın diferansiyel puls voltammogramları (DPV'ler) kaydedilerek gerçekleştirilmiştir. Puls zamanı, puls genliği, basamak potansiyeli ve tarama hızı +530 mV'deki katodik pik (K1) ve -120 mV'deki ikinci katodik pik (K2) için 1 ms, 200 mV, 10 mV ve 50 mV/s olarak optimize edilmiştir. Benzer şekilde +550 mV'deki anodik pik (A1) için 1 ms, 200 mV, 7 mV ve 50 mV/s olarak optimize edilmiştir. Yaklaşık +530 mV'daki K1, -120 mV'deki K2 ve +550 mV'deki A1 sırasıyla 1 -1000 nM, 2,5 - 1500 nM ve 2,5- 1000 nM aralığında doğrusal yanıtlara ve 0,36, 0,79 ve 0,69 nM belirtme alt sınırlarına (Limit of Dedection, LOD) sahip olduğu tespit edilmiştir. İki farklı konsantrasyonda (50 ve 250 veya 500 nM) ETK için % 5'in altındaki RSD değerleri, önerilen elektrodun kabul edilebilir gün içi ve günler arası tekrarlanabilirliğe sahip olduğunu göstermiştir. Son olarak, önerilen yöntem karbidoba, levodapa ve ETK'yı birarada içeren farmasötik tablette ETK'yı tayin etmek için uygulanmış ve tablette belirtilen 200 mg değerine oldukça yakın sonuçlar elde edilmiştir. Ayrıca, ETK eklenmiş yapay idrar örneği ile yapılan çalışmalarda ise % 100'e yakın geri kazanımlar elde edilmiştir. Tüm bu sonuçlar, geliştirilen voltammetrik yöntemle ETK'nın doğru, seçici ve hassas bir şekilde gerçek örneklerde tayin edilebileceğini yansıtmaktadır.
  • Küçük Resim
    Öğe
    Simple, sensitive, and cost-effective voltammetric determination of salbutamol at a pencil graphite electrode modified with Nafion and functionalized multi-walled carbon nanotubes
    (Springer, 2024) Dilgin, Didem Giray; Vural, Kader; Karakaya, Serkan; Dilgin, Yusuf
    This study describes a simple, highly sensitive, and cost-effective electrochemical determination of salbutamol (SBT) at a disposable pencil graphite electrode modified with Nafion/functionalized multi-walled carbon nanotubes composite material (Nf/f-MWCNTs/PGE). The electrochemical response of SBT at this modified electrode was investigated by both differential pulse voltammetry (DPV) and cyclic voltammetry techniques. The voltammetric measurements confirmed that the combination of f-MWCNTs with Nafion shows remarkable electrocatalytic activity on the oxidation of SBT due to a synergistic effect of Nafion via electrostatic interaction and f-MWCNTs via excellent conductivity and large specific surface area. Differential pulse voltammetry results show that the composite electrode gives two linear ranges of 0.10-17.5 mu M and 17.5-100 mu M with a detection limit (LOD) of 0.027 mu M SBT. Moreover, the studies of some potential interferants show that there is no significant interference in the determination of SBT. The proposed procedure was successfully applied to determine SBT in tube- and syrup-type pharmaceutical formulations, animal feed, and beef meat samples, and acceptable results were obtained with high accuracy and precision. Moreover, the proposed sensor displays good intra-day and inter-day precisions for the voltammetric determination of SBT.
  • Küçük Resim
    Öğe
    Voltammetric determination of Molnupiravir used in treatment of the COVID-19 at magnetite nanoparticle modified carbon paste electrode
    (Elsevier Inc., 2023) Vural, Kader; Karakaya, Serkan; Dilgin, Didem Giray; Gökçel, Hatice İsmet; Dilgin, Yusuf
    To reduce the progression of the viral process in patients infected with COVID-19, new treatments and drug active substances are needed. One of these drugs is Molnupiravir (MNP) which has a direct antiviral effect and has also proven to be highly effective in reducing the azopharyngeal SARS-CoV-2 infectious virus and viral RNA. Due to the importance and frequent use of this drug in the treatment of COVID-19, its accurate, quick, and cheap detection in pharmaceutical or biological samples is crucial. In this work, electrochemical behavior and sensitive voltammetric determination of MNP are described using a magnetite nanoparticle modified carbon paste electrode (Fe3O4@CPE) for the first time. Fe3O4 nanoparticles (NPs) were characterized by recording their transmission electron microscopy (TEM) images, energy dispersive X-ray (EDX), and X-ray diffraction (XRD) spectra. Cyclic voltammetric measurements showed that MNP was irreversibly oxidized at Fe3O4@CPE at 760 mV in pH 2.0 Britton Robinson buffer solution (BRBS). The peak current of MNP was increased approximately threefold at Fe3O4@CPE compared to bare CPE due to a good electrocatalytic efficiency of Fe3O4 NPs. According to differential pulse voltammetric studies, the fabricated electrode exhibited a linear range (LR) between 0.25 and 750 µM with sensitivity and limit of detection (LOD) of 4591.0 µA mM−1 cm−2 and 0.05 µM, respectively. On the other hand, although lower sensitivity (327.3 µA mM−1 cm−2) was obtained from CV compared to DPV, a wider linear calibration curve between 0.25 and 1500 µM was obtained in CV. Studies performed in tablet samples confirmed that the Fe3O4@CPE exhibits high applicability for selective and accurate voltammetric determination of MNP in real samples.