Browsing by Author "Negussie Negash"

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    Determination of the Levels of Selected Heavy Metals in Lepidium Sativum Seed Using Flame Atomic Absorption Spectroscopy (FAAS)
    (Addis Ababa University, 2024-08) Desalegn Abere; Negussie Negash
    Traditional medicines have been used thousands of years with a great contribution made by human practice. One of the important traditional medicinal plant is Lepidium sativum or fetto in Amharic belonging to mustard family. The levels of heavy metals (Cr, Ni, Cu, Zn, Cd, and Pb) in Lepidium sativum were determined. The mean concentrations or levels of heavy and trace metals, Zn, Cd, and Pb in the seed of the selected medicinal plant were found to be (in mg/L) 0.6874±0.0029, 0.0094±0.0028, and 0.3695±0.0013 respectively. The mean concentration of metals obtained in the sample were in the order of Zn>Pb> Cd. The concentrations of these trace metals were relatively higher than the maximum allowable concentration given by WHO. But the remaining three metals (Cr, Ni, and Cu) were below detection limit. Furthermore, monitoring such medicinal plants for heavy and trace metals concentrations is of great importance in protecting the community from the adverse effects of the heavy metals.
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    Electrochemical Determination of Gallic Acid in Red Wine, Black Tea and Green Tea Based on Choline Chloride Modified Glassy Carbon Electrode
    (Addis Ababa University, 2024-08) Getachew Amsalu; Negussie Negash
    A sensitive and selective square wave voltammetric approach for determination of Gallic acid (G.A) was developed based on choline chloride modified glassy carbon electrode (ChCl/GCE). The modification was simple and cost effective, which was performed through electrochemical deposition of choline chloride onto the glassy carbon electrode surface using cyclic voltammetry technique. Electrochemical methods including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used for characterization of the modified electrode. It was also effectively employed for the detection of G.A using cyclic voltammetry and square wave voltammetry (SWV) techniques. From the electrochemical investigation, choline chloride exhibited excellent electro catalytic behavior for the detection of G.A and increased electron transfer rate. The effects of several electro analytical experimental conditions were also optimized for sensitive determination of G.A. The irreversible electrochemical behavior of G.A at the ChCl/GCE is an adsorption controlled process involving transfer of electrons. Under the optimized conditions, the SWV result indicated that the oxidation peak current of G.A at the ChCl/GCE was directly proportional to its concentration over linear range of 1.6 μM to 240 μM with limit of detection 0.126 μM, limit of quantification 0.419 μM. The ChCl/GCE has also showed excellent selectivity, reproducibility and long-time stability towards the electrochemical oxidation of G.A. Moreover, the practical applicability of the prepared ChCl/GCE was evaluated in order to determine G.A in red wine, black tea and green tea samples with recovery ranging from 92.20 % – 1
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    Studies on Perchlorate And Hydrogen Phthalate Liquid Membrane Electrodes Based on Crystal Violet and Brilliant Green
    (Addis Ababa Universty, 1988-06) Negussie Negash; Chandravanshi B.S. (PhD)
    Liquid membrane holders were designed from concentric pyrex tubes by glass blowing and employed to design perchlorate and hydrogen phthalate electrodes based on Crystal Violet perchlorate and Brilliant Green hydrogen phthalate salts. Polyviny chloride discs , with 1-chloronaphthalene as plasticizer , were used to support the liquid membranes which consisted of nitrobenzene, 1 , 2-dichloroethane or 1, 2 -dichlorobenzene in the case of Crystal Violet perchlorate and nitrobenzene in the case of the other. Several electroanalytical parameters have been evaluated and both perchlorate and hydrogen phthalate electrodes respond to perchlorate , periodate , Iodide , saccharin , and hydrogen phthalate, with selectivity in that order. The electrodes were found to respond to these anions within 60 seconds , in wide concentration ranges ( slopes 52-60 mv / decade ) with detection limit of 6.7x10“ ^ to 4.7xlO~ ^M. The perchlorate electrode was employed to determine perchlorate in artificial samples with three potentiometric methods and results were found to have reasonable accuracy and precision