Browsing by Author "Alemayehu, Denekew"

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    A Graduate Seminar Report on Solution of Mixed Strategies Problems in Game Theory
    (Addis Ababa University, 2005-06) Alemayehu, Denekew; Ahmad, Mobin (PhD)
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    Square Wave Anodic Stripping Voltammetric Determination of Hg(Ii) With N-P-Chlorophenylcinnamohydroxamic Acid Modified Carbon Paste Electrode
    (Addis Ababa University, 2019-01-05) Alemayehu, Denekew; Tessema, Merid (PhD)
    In this study a new method for the electrochemical determination of Hg(II) ions using N-pchlorophenylcinnamohydroxamic acid (CPCHA) modified carbon paste electrode has been developed. The experiments were carried out using square wave anodic stripping voltammetry (SWASV). The Hg(II) was accumulated on the electrode surface by the formation of the complex in an open circuit and the resulting surface was characterized by medium exchange followed by electrochemical reduction and SWASV for the determination of Hg(II). Experimental parameters, including carbon paste composition, pH and concentration of accumulating and stripping solutions, preconcentration time, Hg(II) concentration and different instrumental parameters were investigated. The optimum voltammetric response was observed for a paste composition of 7.5% w/w (CPCHA to graphite powder in the carbon paste) and preconcentration time of 210 s in 0.1 M sodium acetate at pH 8 followed by electrochemical SWASV in 0.3 M ammonium chloride solution at pH 4 as supporting electrolyte, a reduction potential of -0.6 V with 60 s reduction time. Under these optimal experimental conditions, the voltammetric signals were linearly dependent on the Hg(II) concentration in the range of 1-25 μM with a detection limit of 12.9 nM at the signal noise ratio (S/N = 3). For six measurements, the voltammetric response was reproduced with 3.8% relative standard deviation (RSD) at 15 μM Hg(II). Rapid and convenient renewal allows the use of a single modified electrode surface in multiple analytical determinations over several weeks. Many coexisting metal ions had little or no effect on the determination of Hg(II). Five “spiked” samples of water were evaluated by using the developed method giving recoveries of Hg(II) in the range 98-105%.