Browsing by Author "Tessema, Merid"

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    Electrochemical determination of phenothrin in fruit juices at graphene oxide-polypyrrole modified glassy carbon electrode
    (Elsevier, 2018) Tefera, Molla; Tessema, Merid; Admassie, Shimelis; Iwuoha, Emmanuel I.; Waryo, Tesfaye T.; Baker, Priscilla G.L.
    An electrochemical sensor was developed based on graphen oxide-polypyrrole modified glassy carbon electrode (GO/PPy/GCE) for sensitive determination of phenothrin in fruit samples. GO/PPy/GCE was characterized by scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), Ultraviolet-Visible spectroscopy (UV–Vis) and Raman spectroscopy. The sensor was also characterized using electrochemical impedance spectroscopy and cyclic voltammetry. Compared to bare GCE, GO/GCE and PPy/GCE, the reduction peak current of phenothrin increased significantly at GO/PPy/GCE, demonstrating that GO/PPy/GCE exhibited electrocatalytic activity towards the reduction of phenothrin. Under the optimal conditions, the sensor showed a linear relationship over the range of 2.5×10−8-2.0×10−5 M with detection limits of 13.8×10−9 M. In addition, the analytical application of the proposed method was carried out by the determination of phenothrin in fruit juice samples.
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    Sensitive electrochemical determination of ethambutol in pharmaceutical formulation and human urine at nickel nanoparticles/electrochemically reduced graphene oxide modified electrode
    (Chemical Society of Ethiopia, 2019) Mekassa, Birhanu; Baker, Priscilla G.L.; Chandravanshi, Bhagwan Singh; Tessema, Merid
    This paper describes the application of nickel nanoparticles decorated electrochemically reduced graphene oxide modified glassy carbon electrode (NiNPs/ERGO/GCE) for the determination of ethambutol (ETB), an anti-Mycobacterium tuberculosis drug. The modified electrode showed remarkable electrocatalytic properties accompanied with a significant enhancement in the peak current response towards ETB compared to the bare electrode. The results showed that the composite modified electrode played a significant catalytic role due to the synergetic effect of NiNPs and ERGO. The NiNPs/ERGO modified electrode demonstrated excellent square wave voltammetric response towards ETB determination at the NiNPs/ERGO/GCE in the range 0.05‒100 μM. The sensor demonstrated outstanding sensitivity towards ETB determination with limit of detection (LOD) and limit of quantification (LOQ) of 0.023 and 0.075 μM, respectively. The developed sensor was effectively validated for real sample study using drug formulation and urine samples which showed an acceptable recovery (99.6‒109%). The electrode also exhibited good precision (RSD < 1%, n = 20), reproducibility (RSD < 1.9%, n = 3), long-term stability (92% of its initial response after two weeks) and selectivity towards interfering substances in the determination of ethambutol.