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    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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    Highly sensitive voltammetric determination of the fungicide fenhexamid using a cost-effective and disposable pencil graphite electrode
    (Springer Wien, 2024) Ersan, Teslime; Giray Dilgin, Didem; Oral, Ayhan; Skrzypek, Slawomira; Brycht, Mariola; Dilgin, Yusuf
    A differential pulse voltammetric (DPV) method is proposed for the highly sensitive determination of fenhexamid (FHX) based on both electrooxidation and electroreduction processes using a disposable and cost-effective pencil graphite electrode (PGE). The electrochemical oxidation and reduction mechanisms of FHX at the PGE were elucidated by recording cyclic voltammograms at various pH values of Britton-Robinson buffer (BRB) solutions at a scan rate of 50 mV s-1 and different scan rate values in the range 10-400 mV s-1 at selected pH of BRB (pH 2.0). Differential pulse voltammograms recorded under optimized conditions revealed an oxidation peak of FHX around + 0.65 V and a reduction peak of FHX around + 0.45 V. The DPV analysis of FHX revealed two linear ranges: 0.001-0.01 mu mol L-1 and 0.01-5.0 mu mol L-1 for the anodic peak, and 0.001-0.1 mu mol L-1 and 0.1-5.0 mu mol L-1 for the cathodic peak. The limits of detection were 0.34 nmol L-1 and 0.32 nmol L-1 for the anodic and cathodic peaks, respectively. The proposed methodology demonstrated satisfactory selectivity, as selected pesticides, certain electroactive compounds, and cationic species tested did not interfere with the voltammetric determination of FHX, particularly during its reduction. The recovery results, showing values close to 100% obtained from the analysis of real samples spiked with FHX, indicated that this methodology can accurately determine FHX in water and soil samples.