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Item Phytochemical Investigation on the Leaves of Securidaca longipedunculata(Addis Ababa University, 2024-08) Emebet Demie; Mekonnen AbebayehuSecuridaca lonpeduculata is a well-known medicinal plant in the family of polygalaceae.The plant is locally known as “Itsemenahi’’ Amharic and “temenayi’’ in Afanoromo. It is traditionally used in headache, fever, epilepsy, asthma and cough. The different parts of S. longipeduculata have different purpose, in different countries, for example the root of this plant is used for treatment of fever, malaria, toothache in Nigeria, the leaves are used for treatment of headache skin infection in Nigeria and the steam bark is used for skin disease in Burkina Faso. Phytochemical investigation on the leaves of this plant resulted in the isolation of two compounds (SLE-6andSLE-7). Compound SLE-6 is flavonoid glycoside, compound SLE-7 is a group of galotannins namely: 1. Quercetine-3-O-L-arabinopyranoside. 2.1,5-Anhydro-D-glucitol Structural elucidations of those compounds are based on UV, 1D NMR (1H, 13C &DEPT-135) and 2D NMR (COSY, HSQC &HMBC) spectroscopic data obtained in comparison with similar compounds isolated from the plant.Item Dynamic Variable Temperature NMR Investigation of Tautomerism in Nicotinamide(Addis Ababa University, 2024-08) Dejene Girma; Mesfin RediDynamic Variable temperature proton nuclear magnetic resonance (1H NMR) spectrometry has been used to study variable temperature nicotinamides. A functional group with limited rotation around the C-N bond, the dynamic nicotinamide bond is studied using variable temperature (VT) 1H NMR spectroscopy. The majority of the structural and stereochemical characteristics of an organic compound can be revealed by 1H NMR spectroscopy, which is categorized under the category of 1H NMR spectroscopy or proton magnetic resonance (PMR) spectroscopy in conjunction with 13C NMR. A compound's potential carbon atom composition and number of non-equivalent carbon atoms can both be ascertained from its 13C-NMR spectra. As a result, 13C-NMR offers precise information about a molecule's carbon skeleton. The amide molecule in the studies exhibited two separate peaks, each of which corresponded to the amine group. The peak separation decreased with increasing temperature, suggesting the presence of a rotating barrier around the amide bond. At 328 K, the two peaks were seen to combine. Acetonitrile and chloroform, two generally nonpolar solvents, cause amide and related compounds to undergo substantial temperature-dependent structural changes, according to variable-temperature 1H NMR investigations. The behavior that has been seen indicates that the rotational barrier about the C=N bond cannot be the cause of the peak splitting. Instead, it implies that a tautomeric equilibrium is the cause of the two peaks, which come from two distinct chromophores (O-H and =N-H chromophores).Item Analytical Sample Preparation Methods Based on Miniaturized Extraction for Trace Level Enrichment of Selected Pesticide Residues from Environmental Water and Food Samples Utilizing High Performance Liquid Chromatographic Analysis(Addis Ababa University, 2023-11) Habtamu Bekele; Negussie MegersaThe development and implementation of more environmentally friendly and sustainable microextraction techniques in recent years has provided alternative to traditional sample preparation approaches. In this thesis, we developed, optimized and validated different micro extraction methods for trace level multi residue and multiclass trace level pesticides from environmental water and food samples prior to their determination using chromatographic techniques. Salt assisted graphene oxide (GO) was utilized as a sorbent in dispersive solid phase extraction (DSPE), to enhance and extract certain s-triazine herbicides from environmental water samples. GO can generate scattered colloids in the aqueous phase and offers an extensive variety of functional groups for hydrogen bonding or electrostatic interaction with benzene ring organic compounds with functional groups comprising oxygen and nitrogen. GO was synthesized by modified Hummers method and characterized with Fourier transform infrared (FT-IR) spectroscopy. As complete collection of GO after adsorption process is difficult task, in this established salt-assisted (SA)-GO-DSPE method, it was found to be aggregated and centrifuged in the presence of NaCl. The optimum value for main parameters that influenced extraction efficiency were investigated. Under the optimized conditions, low limits of detection (LODs) (0.12–0.80 ng mL−1), limits of quantification (LOQ) (0.4–2.68 ng mL-1), and good extraction recoveries (69.06–95.53%) were obtained for simultaneous extraction of simazine, atrazine, propazine and prometryn. The relative standard deviations (RSD) of intra-day (n = 6) and inter-day (n = 9) precisions were 2.54 to 5.84% and 4.38 to 8.56%, respectively. When the method's applicability was ultimately assessed, the target analytes in the real water samples weren't detected. The proposed method is environment friendly and promising for trace analysis of other pesticides including the target herbicides in environmental water samples. Dispersive liquid–liquid microextraction based on surface floating organic droplet was designed to enable development of simple, fast, and environmentally friendly analytical technique utilizing for selective and quantitative enrichment of trace level pesticide contaminants from different fruit juice samples for subsequent detection by high pressure liquid chromatography–diode array detection (HPLC–DAD). The optimized method was investigated using spiked blank sample, and results of linearity at concentration levels from 3 to 1500 ng mL-1, with correlation coefficients (r2) ≥ 0.998 were obtained. LOD and LOQ were ranged from 1.3×10−2 to 5.3×10−2 μg L−1 and 4.2×10−2 to 1.8×10−1 μg L−1, respectively. Satisfactory accuracy, i.e, recoveries ranging from 87.23 to 99.45%, with %RSD between 1.37 and 8.39, and precision in terms of %RSD ≤ 10.78 were investigated. At the end, the method was successfully applied to analyze real fruit juice samples and target analytes were not detected in real samples. A simple, selective and fast salting out assisted liquid–liquid extraction (SALLE) technique coupled with HPLC–DAD was developed and optimized for extraction, and analysis of seven multiclass pesticide residues in pasteurized and raw cow milk samples. Under optimum conditions, for broad linear range concentration of 2–1500 μg L-1, r2 was within a range of 0.9982–0.9997. Reliable sensitivity was achieved with LODs and LOQs ranging from 0.58–2.56 ng mL-1 and 1.95–8.51 ng mL-1, respectively. While precision with intra-day and inter-day in terms of RSDs were observed in the range of 1.97–7.88% and 4.52–8.13%, respectively. The results of the precision studies reveal that good repeatability and reproducibility (RSDs < 9%) were achieved. Finally, the validated approach was effectively used to extract and determine pesticide residues in real milk matrices, however the target analytes were not detected in all samples. High density dispersive liquid–liquid microextraction method coupled HPLC-DAD was developed for extraction, enrichment and determination of six sulfonylurea herbicides; namely, metsulfuron-methyl, chlorosulfuron, niclosulfuron, prosulfuron, flazasulfuron and chlorimuron-ethyl in matrices of environmental waters. The optimum experimental parameters that influenced extraction efficiency were investigated. Under the optimized conditions, wide linear calibration curves with r2 > 0.997, LODs in the range of 0.8–1.5 ng mL−1, and LOQ in the range of 1.9–5.1 ng mL−1 were obtained. The precisions in terms of % RSDs of intra-day (n = 6) and inter-day (n = 9) were found to be 3.01 to 8.36 and 2.92 to 9.78, respectively. Applicability of the developed method was investigated by analyzing spiked tap, lake, river and underground water samples and satisfactory recoveries were obtained in the range of 84.3–101.7% with RSDs < 9.8% (n=6) and the target analytes were not detected in real samples.Item Template Synthesis and Characterization of Cd (II) and Cr (III) Schiff Base Metal Complexes Derived from Ethylenediamine, Acetyl Acetone and Dithiocarbamates(Addis Ababa University, 2024-08) Haile Zerihun; Yonas ChebudeCd (II) and Cr (III) Schiff base complexes were synthesized by template synthesis method. Cd (II) hydrated salts was reacted with Acetylene acetone and ethylenediami-ne in 1:2:1 molar ratios and Cr (III) anhydrous salt was reacted with Acetylene acetone, carbon disulfide and ethylenediamine in 1:1:2:2: molar ratios and N,N bis(acac)en Schiff base was synthesized by mixed en and acac in 1:2 molar ratios. Schiff base Cr (III) complex were coloured but Cd (II) complex was colourless. The product obtained Schiff base, Cr (III) and Cd (II) complexes were structurally investigated on the basis of conductance, magnetic susceptibility, IR, NMR etc. studies. The conductivity measurement of synthesized Cr (III) complex showed electrolyte, but Cd (II) complex was non-electrolyte and magnetic susceptibility showed Cr (III) complex was paramagnetic and Cd (II) was diamagnetic. At the last it is proposed that both the Cd (II) and Cr (III) complexes were showed octahedral geometry.Item 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 NegashA 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 % – 1Item 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 NegashTraditional 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.Item Novel Development of Ionic Liquid-Based Copolymer Solid Electrolyte for High-Performance all Solid-State Supercapacitor(Addis Ababa University, 2024-03) Demelie Yimer; Girum AyalnehIn the early 1970s, solid-state materials such as ceramic, glass, crystal, and polymer electrolytes were developed for the purpose of energy storage materials. The energy storage technologies are cutting-edge technologies that are essential for renewable energy, energy management, conservation, and storage, which indirectly contribute pollution control, and greenhouse gas mitigation. Development of solid-state polymer electrolytes (SPEs) is one of the strategies for the development of functional solid-state electrochemical energy storage devices. In this research, polymeric ionic liquid based co-polymer solid electrolytes were synthesized with different ratio of polymeric ionic liquids and copolymers. A simple integration approach enables the quadratic copolymer poly (acrylamide-co-diallyldimethylammonium chloride (PAADDAC) to be well incorporated into chitosan (CS) and polymeric ionic liquid networks during synthesis. Physicochemical characterization techniques such as Fourier-transform infrared (FTIR) and Scanning electron microscope (SEM) were carried out for the spectra analysis of Ionic liquid based Chitosan/Poly (acrylamide-co-diallyldimethylammonium chloride) polymer TFSI (PIL &IL-b-CPE) are based on various chemical crossings. And electrochemical characterization methods such as cyclic voltammetry (CV) and charge discharge of the synthesis membrane were tested. The main emphasis was on materials like conducting copolymer solid electrolytes. Parameters like as energy, capacity, power, cycle performance, and equivalent series resistance are used to analyze the performance of solid copolymer electrolytes. On this solid state SC with ionic liquid impregnation ratio of 25% exhibited the best performance with specific capacitance (Cam) and energy density (Emax) of 3.74 F g-1 and 2.07 Wh kg-1, respectively. These records of worth are only slightly lower than those obtained for convectional SCs using pure TFSI, and much higher as compared with other solid SCs based on conventional polymer electrolytes. This is mainly due to the high electrochemical stability of this PIL &IL-b-CPE that allows these solid SCs to operate at maximum voltages as high as 2 V for the first time.Item Removal of Cr(VI) by Adsorption using Milletta Ferruginea Seed Shell (MFSS)(Addis Ababa University, 2024-08) Sintayehu Manahilot; Solomon MehretieWastewater treatment technologies for the removal of hexavalent chromium are currently one of the challenges in developing countries. An adsorbent prepared from Millettia Ferruginea seed shell (MFSS) was used to assess the adsorption of Cr(VI) ions from synthetic wastewater. Numerous factors, including pH, contact time, initial concentration, and dosage of the adsorbent, were optimized. The parameters for Cr(VI) adsorption on the adsorbent were 10 mg of adsorbent, pH 1 and 40 minutes of contact time. 10.55 mg/g was found to be the highest adsorption capacity, and at constant volume, the maximum percentage removal was 55.97%. The adsorption of Cr(VI) on the MFSS adsorbent was shown to obey pseudo-second order kinetics and to follow the Freundlich isotherm model.Item Determination of Selected Heavy Metals in Ocimum Sanctum Sample Using Flame Atomic Absorption Spectroscopy (FAAS)(Addis Ababa University, 2024-08) Zemenay Kekebo; Negussuie NegashFood additive plant have worldwide applications for its acceptability, aroma, color and sweetness of the food. Among the food additive plants of Ethiopia, Ocimum sanctum (in Amharic Besobela) is one of the well celebrated and most widely used home food additive mostly used during the preparation of pepper (berbere in Amharic) to improve the aroma and acceptability of pepper (berbere). The sampling technique used to carry out the analysis was purposive for the community in the selected area because the plant was widely used as food additive, the sample were selected from Bishoftu district in Gudino kebele. The aim of this study is to determine the concentration of selected heavy metal in holy basil (Besobela)sample. For the study 0.5-gram powdered sample that taken from Bishoftu district was digested by mixing 3ml of 69%HNO3and 1 ml of 70% perchloric acid, HClO4 at the temperature of 2700C for 2:40’. The contents of the selected heavy metals (Cr, Pb Cu, Cd, and Zn) in holy basil were determined using FAAS and the obtained concentrations of these metals were compared with limit values set by WHO. The mean content of the selected heavy metals was determined from triplicate samples of holy basil, the mean concentrations of heavy metals analyzed in holy basil samples obtained in mg/l were; Cu(0.373±0.151), Zn(0.832±0.045), Pb(0.415±0.0027), Cd(0.0288± 0.008 ) and Cr(BDL).The mean concentration of heavy metals obtained in holy basil were in the order of Zn> Cu>Pb> Cd and Cr was BDL. The concentration of lead analyzed in holy basil sample exceeded the maximum allowable concentration given by WHO. But the concentration of other metals Zn, Cu, Cr, and Cd were below the guideline set by WHO. The level of analyzed metals in this study are both higher and lower than the concentration of metals reported in different literatures.Item Preliminary Phytochemical Investigation of the Root of Verbascum Sinaiticum (Scrophulariaceae)(Addis Ababa University, 2024-08) Genet Kassaye; Kibrom G/HiwotThe focus of this study was preliminary phytochemical investigation of the methanol extracts of the root of V. sinaiticum (Scrophulaceae). The plant is traditionally used in Ethiopia for various medicinal purposes including wound healing anti-microbial activities. The extraction and characterization of bioactive compounds were conducted using a Cyclohexane: ethyl acetate (2:1) solvent system. The extracts were then analyzed using various spectroscopic methods such as TLC, 1 H-NMR, 13 C NMR and DEPT-135, to elucidate the structural characteristics of the isolated compounds. The isolated compound from the root extract was identified as 9, 12, 15- octadecatrienoic acid or α-linolenic acid (ALA), an essential omega-3 fatty acid known for its potential health benefits. ALA has been linked to various health advantages, including cardiovascular health, diabetes management, renal health, and anti-inflammatory properties.Item Phytochemical Investigation of the Stem Bark of Securida Longipedunculata(Addis Ababa University, 2024-08) Mamite Atlaw; Kibrom G/HiwotPlants traditionally used in Ethiopian medicine for various ailments including venereal diseases, stomachache, dislocated jaw, headaches, skin cancer, skin infections, contraceptive purposes. Securidaca longipedunculata is an important plant species with potential benefits in the treatment of various ailments. In this study, two compounds were obtained (SLM-1 and SLM-2) from the stem bark of Securidaca longipedunculata by using solvent extraction and column isolation. The solvents were ethyl acetate, cyclohexane, methanol, and chloroform. The compounds that were obtained from stem bark of Securidaca longipedunculata SLM-1 is a group of galotannins, which were 1,5-anhydro-D-glucitol and SLM-2 is ketone group which were 2,3-dimethoxy-4-hydroxy benzophenone .From this, 1,5-Anhydro-D-glucitol was the major one, which accounts for 3.46%; on the other hand, 2,3-dimethoxy-4-hydroxy benzophenone accounts for a for a small amount, which was (0.027%) from the plant material. The isolated compounds were characterized by the spectroscopic techniques, which are 1H NMR, 13C NMR, DEPT-135, HMBC and HSQC.Item Determination of Some Heavy Metals in two Selected Medicinal Plants Collected from Sidama Region in Masincho(Addis Ababa University, 2024-09-12) Zerihun Zewde; Negussie MegersaIn this study the collected samples of P. vogeliifruitsand R. myricoides leaves were cleaned, dried in an oven and then ground topowder form. Then 0.5gof each powdered sample was digested with 4 mLof 69.72%ofHNO3 and 1 mLof 70% of HClO4at a temperature of 300℃ for 4:00hrsand 3mLof 69.72% HNO3 and 1 mLof 70% HClO4at a temperature of 300℃ for 3:00 hrs respectively. An efficient wet digestion procedure with the percentage recoveries which range from 99.33-99.97% forP. vogelii and 94.7-98.9% for R. myricoides were developed. The contents of heavy metals (Cu, Cr, Cd, Zn and Pb) in P. vogelii and R. myricoides samplesweredetermined using FAAS and the result of mean concentrationsof these metals were compared with the limit values set by WHO. The mean concentrations of the selected heavy metals were determined from triplicate samples of P. vogelii and R. myricoides herbal medicinal plantswhichwere grown in Masincho area near Yirgalem town of Sidama region.In the present study, the mean concentrations of selected heavy metals analyzed inP. vogelii and R. myricoides samplesin mg/kg were Zn (75.23± 0.038), Cu (17.68± 0.023), Pb (10..66± 0.0019),Cd (3.15± 0.0066) and Cr (BDL);and Zn (10.50± 0.0098), Cu (34.98± 0.006), Cd (8.70 ±0.0063), Pb (18.60 ±0.0072) and Cr (BDL) respectively. The contents of chromium were too lowto be measured in both sampleswhich werebelow detection limit and therefore,were not reported.The levelsof theseanalyzed metals in this study are both higher and lower just likethe concentrations of metals reported indifferent literatures in medical plant fruits and leaves.Item Advanced Electrochemical Sensors for the Determination of Selected Antibiotic Drug Residues in Food and Water Samples(Addis Ababa University, 2024-06) Wondimeneh Dubale; Merid Tessema; B. S. ChandravanshiThe presence of antibiotic drug residues in food and water sources poses a critical challenge to the public health and environmental sustainability. Addressing this challenge requires the development of highly sensitive and selective detection methods capable of accurately quantifying trace levels of the residues in complex sample matrices. The aim of this study was to contribute to this vital area of research by focusing on the designing, fabrication, characterization, and application of advanced electrochemical sensors for the detection of antibiotic residues in various matrices. In this study, eight cutting-edge electrochemical sensors were developed, characterized, and successfully applied for the individual and simultaneous determination of selected antibiotic drug residues in food and water samples. Through thorough experimentation and optimization, novel electrochemical sensor architectures have been developed using innovative materials, including gold-silver alloy nanocoral clusters (Au-Ag-ANCCs), thermally annealed gold–silver alloy nanoporous matrices (TA-Au-Ag-ANpM), iron-doped polyaniline (Fe-dop-PANI), nickel oxide nanoparticles (NiO-NPs), zinc oxide nanoparticles (ZnO-NPs), functionalized multi-walled carbon nanotubes (f-MWCNTs), reduced graphene oxide (r-GO), poly(L-histidine), poly(L-serine), poly(glycine), polyethylene oxide (PEO), and choline chloride (ChCl), to improve sensitivity, selectivity, and stability. The surface morphology, elemental composition, and electrochemical properties of the developed sensors were characterized using an array of analytical techniques, including UV–Vis spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction spectroscopy (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). Among the developed sensors, ChCl/CPE was designed for the determination of ciprofloxacin (CPRO) in eye drops, river water, and egg samples. It exhibited outstanding performance with a wide linear range (0.005–200 μM), and impressive detection and quantification limits of 0.36 nM and 1.2 nM, respectively. ChCl/GCE was prepared for the simultaneous determination of tinidazole (TIN) and chloramphenicol (CAP) in egg, honey, and milk samples. It showed exceptional detection capability with a wide linear range of 0.010–170 μM and 0.005–300 μM for TIN and CAP, respectively. The limit of detection (LOD) and limit of quantification (LOQ) were 0.90 nM and 3.0 nM for TIN, and 0.27 nM and 0.89 nM for CAP, respectively. TA-Au-Ag-ANpM/r-GO/poly(glycine)/GCE was developed for the detection of life-threatening residues of metronidazole (MTZ) in milk powder, pork, and chicken meat samples. It performed exceptionally in the detection of MTZ with a wide linear range from 2.0 pM to 410 μM. The LOD and LOQ were determined to be 0.0312 pM and 0.104 pM, respectively. Au-Ag-ANCCs/r-GO/poly(L-histidine)/GCE was used for the simultaneous determination of vancomycin (VAN) and ceftriaxone (CFT) residues in chicken meat, fish, and milk samples. The sensor demonstrated outstanding performance in the determination of the analytes over a wide dynamic range, from 1.0 pM to 120 μM for VAN and from 1.0 pM to 290 μM for CFT. The LOD and LOQ values were determined to be 0.11 pM and 0.36 pM for VAN and 0.017 pM and 0.057 pM for CFT, respectively. TA-Au-Ag-ANpM/f-MWCNTs-CPE/poly(L-serine) was prepared for the simultaneous detection of sulfathiazole (SFT) and sulfamethoxazole (SFM) residues in honey, beef, and egg samples. It showed exceptional performance in a wide linear range (4.0 pM to 490 μM for SFT and 4.0 pM to 520 μM for SFM), with picomolar detection and quantification limits (0.53 pM and 1.75 pM for SFT, 0.41 pM and 1.35 pM for SFM). Au-Ag-ANCCs/f-MWCNTs-CPE/ChCl was developed for the simultaneous determination of rifampicin (RAMP) and norfloxacin (NFX) residues in water samples. It exhibited outstanding performance in a broad linear range, from 14 pM to 115 μM for RAMP and from 0.9 nM to 200 μM for NFX, with LOD and LOQ values of 2.7 pM and 8.85 pM for RAMP and 0.14 nM and 0.47 nM for NFX, respectively. Au-Ag-ANCCs/ZnO-NPs-CPE/PEO was prepared for the simultaneous detection of nitrofurantoin (NFT) and furazolidone (FZD) in poultry, fish, honey, dairy products, and municipal wastewater samples. The sensor demonstrated exceptional performance over a wide linear range, from 1.0 pM to 250 μM for NFT and 0.9 nM to 360 μM for FZD. The LOD and LOQ were found to be 0.26 pM and 0.88 pM for NFT and 0.023 pM and 0.076 pM for FZD, respectively. Finally, TA-Au-Ag-ANpM/Fe-dop-PANI/NiONPs/GCE was developed for simultaneously determining azithromycin (AZM) and enrofloxacin (ENF) residues in food and water samples. The sensor exhibited exceptional performance in a broad dynamic range from 0.8 pM to 250 μM for AZM and 0.1 pM to 550 μM for ENF, with LOD and LOQ values of 0.053 pM and 0.18 pM for AZM and 0.013 pM and 0.042 pM for ENF, respectively. In order to maximize the efficiency of the proposed sensors, an extensive optimization of various experimental parameters was performed. The optimization process included the selection of the appropriate supporting electrolytes, choice of the pH of the electrolyte solutions, determination of the number of electropolymerization cycles, optimization of the mixing ratio of the nanocomposites, adjustment of the volume of the drop-casting species, and selection of the square wave voltammetry (SWV) parameters, such as amplitude, frequency, and step potential, as well as other instrumental parameters. Under these optimized experimental conditions, the developed sensors exhibited remarkable selectivity and effectively discriminated between the target analytes and interferents present in complex sample matrices. In addition, the developed sensors exhibited exceptional reproducibility, repeatability, and long-term stability. Subsequently, the developed sensors were validated using real food and water samples that were suspected to contain antimicrobial drug residues. The results revealed impressive recoveries ranging from 95.6 to 103%, with relative standard deviations below 5%. In general, the results presented in this paper represent a significant advance in the field of electrochemical sensor technology, particularly in the vital area of identifying antibiotic residues in food and water samples. The introduction of these state-of-the-art sensors heralds a new era characterized by increased sensitivity, selectivity, and reliability. This advancement will change the landscape of monitoring, regulating, and controlling antibiotic residues in food chains and water sources. Beyond enriching scientific knowledge, this breakthrough offers tangible benefits for public health and environmental sustainability, and embodies the laudable pursuit of advancing knowledge for the benefit of society.Item Phytochemical Studies of Myrica Salicifolia, Clematis Simensis and Olinia Usambarensis(Addis Ababa University, 2024-06) Abraham Dilnesa; Mekonnen Abebayehu; Estifanos EleMyrica salicifolia A Rich (Myricaceae) is a tree growing in Central and East Africa. Traditionally the plant is applicable in the treatment of malaria, respiratory disorders, inflammations, and infections. The leaves and stem barks of Clematis simensis are traditionally used to treat tinea capitis, dermatitis, tropical ulcers, wounds and cancer. One of the African medicinal plants, Olinia usambarensis, is well known for its traditional use in various forms of medicine to treat fever, respiratory issues, digestive issues, headaches, and scabies. In this study, the plant materials were collected from Debresina, and Northern Shewa, Ethiopia. The essential oil extractions of the samples were carried out via hydrodistillation. The composition of the essential oil from roots and leaves of Myrica salicifolia, aerial part of Clematis simensis, and barks of Olinia usambarensis was analyzed by GCMS. A total of 79 compounds were identified by GC-MS. The major compounds in the essential oils from roots and leaves of Myrica salicifolia were trans-3-hexen-1-ol (52.62%) and n-hexadecanoic acid (46.69%). On the other hand, the essential oil obtained from the aerial part of Clematis simensis and barks of Olinia usambarensis were predominantly (E)-2-nonen-1-ol (38.33%), 4-cyclopentene-1,3-dione (28.69%), and n-hexadecanoic acid (28.83%). Three terpenes, namely squalene (77), β-carotene (78), and β-sitosterol (80), and one chlorin, namely pheophytin a (79), were isolated from the leaves of M. salicifolia. The chloroform-methanol (2:1) crude extract of the stem barks of M. salicifolia was fractionated using column chromatography to afford three diarylheptanoids (myricanone (28), myricanol (29), myricanol-11-O-β-D-xylopyranoside (32)), four triterpenoids (taraxerone (81), taraxerol (82), myricadiol (83), 3β-O-trans-caffeoylisomyricadiol (84)), one pyranoside (methyl-β-D-glucopyranoside (85)). This is the first report of compounds 81, 82, 83, 84, and 85 from the stem barks of M. salicifolia. Five compounds, namely taraxerol (82), β-sitosterol (80), sitoindoside I (87), myricanone (28), and myricanol 5-O-β-D-glucopyranoside (30), were also isolated from the roots of M. salicifolia. Furthermore, three compounds, namely 2-deoxy-D-ribono-1,4-lactone (88), 5-hydroxylevulinic acid (89), and β-sitosterol-3-O-β-D-glucoside (90), were isolated from the aerial part of Clematis simensis. Three compounds, namely lupeol (91), n-pentacosyl trans-ferulate (92), and 4-O-β-D-glucopyranosylcaffeic acid (72), were isolated and characterized from the barks of Olinia usambarensis. The structures of these compounds were determined using a comprehensive analysis of 1D/2D NMR, HR-MS, FT-IR and comparison with literature data. In this work, the isolated compounds and crude extracts of Myrica salicifolia, and aerial part of Clematis simensis were screened for antibacterial activity using disk diffusion agar method, and the activities revealed that both myricanol-11-O-β-D-xylopyranoside (32) and 3β-O-trans-caffeoylisomyricadiol (84) showed modest antibacterial activity with inhibition zones of 10.0 mm against S. pyogenes and 9.0 mm against S. aureus at 250 μg/mL. The antioxidant activities of the crude extracts and isolated compounds were also evaluated using the diphenylpicrylhydrazyl (DPPH) assay method. The crude extracts and isolated compounds from the stem barks of Myrica salicifolia, roots of Myrica salicifolia, aerial part of Clematis simensis, and barks of Olinia usambarensis showed very weak (IC50 = 458.8 μg/ml) to very strong (IC50 = 2.97 μg/ml) DPPH scavenging activities. The observed IC50 value showed that roots of Myrica salicifolia exhibited highest antioxidant activity (IC50 = 2.97 μg/ml).Item Computational Investigatio of Mixed MgCl2/ CaCl2/MgSO4 Hydrated Materials for Thermochemical Energy Storage Applications(Addis Ababa University, 2024-06) Debisa Gemechisa; Getachaw Gizaw; Ahmed MustefaBecause of their excellent thermal energy storage, renewable nature, and sustainability, magnesium chloride hydrates have gained a lot of attention as potential energy storage materials.The processes of hydration and dehydration result in the discharge or charging of the MgCl2 salt substance.A magnesium chloride cluster has a higher energy than a MgCl2 formula unit.An effective approach for creating MgCl2 clusters was the computationally artificial bee colony algorithm. In addition, we optimized (MgCl2)n.mH2O and (MgCl2)n to obtain low lyining cluster structure using the VASP software. However, the side reaction known as hydrolysis impedes the cyclic kinetics response that occurs between the dehydration and hydration phases. The hydrolysis reaction and the dehydration reaction occur at different temperature intervals for different clusters.Item A Computational Investigation of Hydrated Magnesium Sulfate Clusters and their FAU Composites for Improved Thermochemical Energy Storage(Addis Ababa University, 2024-06) Belaynew Teshome; Getachew Gizaw; Ahmed MustefaThe effective use of renewable energy sources and the decrease of greenhouse gas emissions are greatly dependent on thermal energy storage, or TES. We report a computational method for examining the hydrate clusters of hydrated magnesium sulfate (MgSO4) and their compounds with faujasite zeolite (FAU) for enhanced performance in thermoelectric sensing (TES). The optimal hydration states and structural characteristics of the hydrated MgSO4 clusters were revealed through modeling with density functional theory (DFT) calculations. Molecular dynamics techniques were used for optimization of composite structure implemented by Vienna Ab initio Simulation Package (VASP) software. After this, the TES capacity, reversibility, and thermal conductivity of the MgSO4 hydrate-FAU composites were assessed. As a result of their superior heat storage properties over their constituent parts, composite materials are a strong contender for advanced thermal energy storage applications, according to the research. This method of computational research gives a logical way to create high-performance thermoelectric solar materials while also shedding light on the interactions at the molecular level.Item Computational Investigation of Ca(OH)2 / CaO for Thermochemical Energy Storage(Addis Ababa University, 2024-06) Sada Husen; Getachew GizawThermochemical energy storage (TCES) systems are essential for improving the efficiency and reliability of renewable energy technologies. Calcium hydroxide (Ca(OH)₂) and calcium oxide (CaO) are promising candidates for TCES due to their high energy density and reversible hydration-dehydration reactions. This study presents a comprehensive computational investigation of Li and Li₂-doped Ca(OH)₂/CaO clusters using the Vienna Ab initio Simulation Package (VASP) and ABCluster software. Clusters of Ca(OH)₂ and CaO with sizes ranging from n=1 to n=10 was prepared, and low-lying isomers were selected for detailed analysis. Density Functional Theory (DFT) calculations were conducted to optimize the geometries and compute binding energy, formation energy, and second-order energy corrections. It is evident from the stability analysis that the doped clusters' average binding energies and formation energies are higher than those of the comparable pure Ca(OH)n and (CaO) clusters. Maximum peaks of the second order energy differences are seen for LiCan−1(OH)n (n=2−10), Li2Can−1(OH)n (n=2−10) and LiCan-1On (n=2-10), Li2Can-1On (n=2-10) clusters at n=6, 4, and 2 suggesting that these clusters are more stable than the clusters that are surrounding them. Clusters with n=6 were specifically chosen for evaluating energy storage potential. Additionally, dehydration curves were plotted to assess the energy release characteristics. The results demonstrate that Li and Li₂ doping significantly enhances the thermochemical properties of Ca(OH)₂/CaO clusters, resulting in higher energy storage density, improved reaction kinetics, and better cycling stability.Item Water Hyacinth-Derived Activated Carbon Paste Electrode for the Electrochemical Determination of Dopamine(Addis Ababa University, 2024-08) Gashaw Girma; Solomon MehretieThe electrochemical determination of dopamine gains great interest due to its important role in the central nervous system (CNS) in various neurological disorders. This study explores the development of a non-toxic and cheap activated carbon paste electrode made from water hyacinth. The activated carbon was synthesized from water hyacinth through a carbonization process followed by chemical activation with phosphoric acid, yielding a material with good electrochemical activity. The synthesized activated carbon was then used to fabricate a carbon paste electrode, which was characterized using cyclic voltammetry (CV). The capacity of the water hyacinth-derived carbon paste electrode to quantify dopamine using differential pulse voltammetry (DPV) in phosphate buffer electrolyte solution. The electrode works with a linear range of 1.0–100 μM and a detection limit of 0.1 μM. The electrochemical sensor was applied to urine sample with a recovery range of 97.1-104.0 % result shown that this electrode could serve as an alternative for dopamine sensing to urine samples. It has different applications, including organic fertilizer, mulching, biofuel, and to clean the sewage. Moreover, this study provides a new application that contributes to the development of green technologies in sensors.Item Density Functional theory Investigations of Benzoquinones Derivatives first and Second Reduction Potential for Redox Flow Battery Application(Addis Ababa University, 2024-08) Getahun Bayou; Yedilfana SetargeQuinones are excellent candidates for organic-based redox-flow batteries due to their high redox potential. In this study, the first and second redox potentials of benzoquinone (BQ) and its derivatives were calculated using the state-of-the-art density functional theory (DFT) tool implemented in Gaussian 09 software at the theory level of B3LYP with 6-311G/d basis set and CPCM solvation model. The BQ derivatives were derived by adding EWD substituents (-CHO, -COCH3, -COOCH3, -CF3, –CN, -NO2Inaddition to the effect of functional groups, solvation free energy, and HOMO-LUMO energies and the reduction potentials was studied. The DFT results revealed that the EWD substituted BQ were found to have the highest first and second redox potentials than EDG substituted BQ. Moreover, the electrochemical behaviour of BQ and its derivatives in n-hexane (C6H14),dimethylsulphoxide (DMSO), and water solvents were studied. Due to the solvent’s hydrogen bonding, polarity, and dielectric constant, the average reduction potential measurements have the following trends: n-hexane less than DMSO and water.Item Determination of Selected Heavy Metals in Fruits of Casimiroa Edulis (White Sapote) by Using Flame Atomic Absorption Spectroscopy (FAAS)(Addis Ababa University, 2024-09) Getye Chalelgn; Merid TessemaThe purpose of this study was the determination of selected heavy metals in fruits of casimiroa edulis samples that were randomly collected from three kebele of Merehabete wereda that is Kofna Sibewasha, Geb Zomoy and Alem Ketema 03 kebele. 0.5 g of oven dried sample was digested by mixing 2ml of 69% HNO3 and 1 ml of 70% HClO4 at a temperature of 240℃ for 2 hrs. The content of heavy metals (Cr, Ni Cu, Cd, Zn and Pb) in fruits of casimiroa edulis was determined using FAAS and obtained concentrations of these metals were compared with limit values set by WHO. The mean content of the selected heavy metals were determined from triplicate samples of fruits of casimiroa edulis, which were grown in three areas of Merehabete wereda. In this study the mean concentrations of selected heavy metals obtained in fruits of casimiroa edulis sample in mg/l were; Ni (BDL), Cd (0.01833±0.00338), Cu (BDL), Zn (0.21205±0.07279), Cr (BDL) and Pb (0.34883±0.0619).The mean concentration of heavy metals obtained in fruits casimiroa edulis were in the order of Pb > Zn > Cd and Cr, Cu and Ni were BDL. The concentrations of all metals (Cr, Ni Cu, Cd, and Zn) were below the guide line set by WHO. However, the concentrations of lead was higher the guide line set by WHO. Because of this they were not safe in terms of health risk. The level of some analyzed metals in this study is lower than the concentration of metals reported in different literatures with other similar family fruits.