Showing papers in "Bulletin of The Chemical Society of Ethiopia in 2008"
TL;DR: In this paper, the levels of total phosphate in selected surface water and groundwater bodies from Manzini and Lubombo regions of Swaziland were determined using UV spectroscopic method.
Abstract: T he levels of total phosphate in selected surface water and groundwater bodies from Manzini and Lubombo regions of Swaziland were determined using UV spectroscopic method. Samples were collected from three rivers (upstream and downstream of each), three industrial effluents, one reservoir, one pond, one tap water and fifteen boreholes. Mean phosphate levels in the tap water and reservoir varied between 0.08-0.09 mg/L while for the river samples, the range was 0.11-0.37 and for the industrial discharge, it was 0.11-1.60 mg/L PO 4 –P. For the ground water systems it ranged between 0.10-0.49 mg/L PO 4 –P. The mean phosphate levels in all the analyzed surface and groundwater samples were below the recommended maximum contaminant level (MCL) by SWSC (Swaziland Water Service Corporation) – i.e. 1.0 mg/L for drinking water; 2.0 mg/L for rivers and industrial effluents, and the South African criterion of 1.0 mg/L PO 4 –P, for sewage effluents being discharged into receiving waters. However, pooled mean values for all the sites were higher than the USEPA criterion of 0.03 mg/L maximum for uncontaminated lakes. Dominant factors considered to have influenced the levels of phosphates in both the surface and groundwater samples analyzed include industrial activities (where present), agricultural activities (including livestock), population density, location (urban, suburban or rural), soil/rock type in the vicinity of the sampling point, climate and rainfall pattern of the area or region concerned. KEY WORDS: Surface water, Groundwater, Limiting nutrient, Eutrophication, Algal bloom, Anthropogenic phosphate sources Bull. Chem. Soc. Ethiop. 2008 , 22(2), 197-206.
74 citations
TL;DR: In this article, the interaction between hydrogen molecules and bare as well as functionalized Si/Ge nanofilm and nanotube was investigated using Monte Carlo (MC) and Langevin dynamic (LD) simulation methods.
Abstract: The nanocrystalline silicon-germanium films (Si/Ge) and Si/Ge nanotubes have low band gaps and high carrier mobility, thus offering appealing potential for absorbing gas molecules Interaction between hydrogen molecules and bare as well as functionalized Si/Ge nanofilm and nanotube was investigated using Monte Carlo (MC) and Langevin dynamic (LD) simulation methods It was found that the binding energy of the H 2 on the Si/Ge surface is weak, and be enhanced by increasing curvature of surface to tube form and increasing temperature The structural, total energy and energy band gaps of H 2 absorbed nanocrystalline silicon germanium film (Si/Ge) and as it passes through Si/Ge nanotube was also studied They are computed with MC and LD simulation the methods at different temperatures All the calculations were carried out using HyperChem 70 program package KEY WORDS: Monte Carlo , Langevin dynamic simulation, Silicon-germanium films (Si/Ge), Si/Ge nanotube Bull Chem Soc Ethiop 2008 , 22(2), 277-286
48 citations
TL;DR: In this paper, the concentrations of trace heavy metals in textile samples collected from Tokat, Turkey, were determined by flame and/or graphite furnace atomic absorption spectrometry after microwave digestion.
Abstract: The concentrations of trace heavy metals in textile samples collected from Tokat, Turkey, were determined by flame and/or graphite furnace atomic absorption spectrometry after microwave digestion. The relative standard deviations for the determinations were found to be lower than 10 %. The concentrations of trace metals in analyzed textile samples were found to be in the range of 0.76-341 µg g -1 for Cu, 0.10-0.25 µg g -1 for Cd, 0.63-4.84 µg g -1 for Zn, 1.02-2.50 µg g -1 for Mn, 3.55-34.3 µg g -1 for Fe, and 1.20-4.69 µg g -1 for Ni, respectively. Copper and cadmium contents in textile products analyzed were found to be higher than limit values given by Oeko-Tex. The results of the present work for textile products are compared with literature values. KEY WORDS: Trace metals, Textile samples, Atomic absorption spectrometry, Microwave digestion, Turkey Bull. Chem. Soc. Ethiop. 2008 , 22(3), 379-384.
42 citations
TL;DR: In this paper, the adsorption of lead(II) on to activated carbon developed from an indigenous Ethiopian medicinal plant leaves namely Birbira ( Militia ferruginea ) was investigated to assess the possible use of this adsorbent.
Abstract: The adsorption of lead(II) on to activated carbon developed from an indigenous Ethiopian medicinal plant leaves namely Birbira ( Militia ferruginea ) was investigated to assess the possible use of this adsorbent. The influences of contact time, adsorbent dose, Pb(II) concentration, pH and temperature on adsorption were investigated. The maximum adsorption took place at 3 h. at a dose of 4.0 g of adsorbent, and 97.3 % of Pb 2+ adsorption at pH of 4.0. The amount of lead ion adsorbed per gram of the adsorbent increased with decreasing concentration of Pb 2+ . The percentage of adsorption had increased with the increasing temperature. The positive value ofH indicated that the adsorption of lead ions on the adsorbent was an endothermic process. The values of free energy ( �G) were negative as expected for a spontaneous process. The decrease inG value with increasing temperature revealed that adsorption of the ion on the adsorbent became favorable at a higher temperature. The calculated value ofH was 25.05 kJ mol -1 , �S was 135.48 JK -1 mol -1 andG was also calculated for each temperature. The two theoretical adsorption isotherms, namely, Langmuir and Freundlich were used to describe the experimental results. The Freundlich adsorption isotherm best fits and adsorption capacity was calculated to be 3.3 mg of Pb(II) per g of adsorbent. The adsorption followed the first order kinetics and was found to be pH dependent being maximum at pH 4.0. The pH effect and desorption studies showed that ion exchange mechanism might be involved in the adsorption process. Reuse of the desorbed bio-adsorbent is possible. The effect of foreign ions on the removal of Pb(II) has been investigated. The removal of Pb(II) from industrial wastewater sample was also tested and showed that more than 97 % removal was possible. The results showed that activated carbon prepared from Birbira ( Militia ferruginea ) leaves could be used for the removal of Pb(II) from wastewater.
38 citations
TL;DR: In this paper, levels of amino acids were determined in the grains of guinea corn, Sorghum bicolor (L.) Moench, and they showed that the steeped sample was best in Lys, Asp, Glu, Leu and Ile.
Abstract: Levels of amino acids were determined in the grains of guinea corn, Sorghum bicolor (L.) Moench. The steeped sample was best in His, Arg, Thr, Ser, Pro, Gly, Ala, Met, Cys, Val, Phe and Tyr contents whereas germinated sample was best in Lys, Asp, Glu, Leu and Ile. The total amino acid contents were: steeped [57.71 g/100 g crude protein (c.p.)], germinated (53.37 g/100 g c.p.) and raw (37.91 g/100 g c.p.) with respective essential amino acids of 30.70 g/100 g c.p., 28.33 g/100 g c.p. and 21.48 g/100 g c.p. Percentage cystine/total sulfur amino acid (% Cys/TSAA) trend was 72.0 (steeped) > 71.1 (germinated) > 58.9 (raw). The Predicted Protein Efficiency Ratio (P-PER) levels were 0.23 steeped, 0.29 (germinated) and none (raw). The Leu/Ile ratio was 0.42 for steeped, 0.38 for germinated and 0.24 for raw grains. The limiting amino acid was Leu for all the samples with 0.30 (steeped), 0.31 (germinated) and 0.16 (raw). The two treatments enhanced the quality of the guinea corn amino acid levels. However, no significant differences occurred between raw/steeped, raw/germinated and steeped/germinated samples at p KEY WORDS: Amino acid quality, Raw, Steeped, Germinated, Guinea corn Bull. Chem. Soc. Ethiop. 2008 , 22(1), 11-17.
25 citations
TL;DR: In this paper, polycrystalline niobium-doped molybdenum and tungsten diselenides were synthesized in silica tubes sealed under secondary vacuum.
Abstract: Polycrystalline niobium-doped molybdenum and tungsten diselenides were synthesized in silica tubes sealed under secondary vacuum. They were characterized by scanning electron microscopy, electron diffraction, X-ray diffraction, chemical composition and EDX analyses. The morphology of niobium-doped molybdenum solid solutions was shown to depend strongly on the conditions of synthesis, whereas the structural characterization did not. KEY WORDS: Polycrystalline niobium-doped molybdenum and tungsten diselenide solid solutions, Doped powders diselenides, Mo 1-x Nb x Se 2 , W 1-x Nb x Se 2 , SEM, X-ray diffraction, Electron diffraction Bull. Chem. Soc. Ethiop. 2008 , 22(2), 225-236.
18 citations
TL;DR: In this article, the authors described the difference of the clay mineralogy in the Permo-Triassic sandstones in the Ulster Basin depending upon the depositional environments, source area geology and burial history of the basin.
Abstract: Adigrat sandstone formation in the Blue Nile Basin is dominated by quartz arenite and subarkosic arenite, and cemented by carbonate, clay minerals and quartz overgrowths. Clay minerals in the Adigrat sandstone formation are dominated by kaolinite, illite and chlorite. Illite is the common grain-coating clay mineral. The common pore-filling minerals are kaolinite, illite and chlorite. The formation reaches a depth of 3km, which facilitated the change of kaolinite to illite. Clay minerals are the major reducer of porosity and permeability in the Adigrat sandstone formation. The Permo-Triassic sandstones in the Ulster Basin were deposited in NE-SW trending fault-bounded asymmetrical graben. The Permo-Triassic sandstones reaches a burial depth of 1/2 km in the marginal areas and 4.5 km in the basin center. The basin underwent multiple episodes of uplift and erosion in the Upper Jurassic, and Mid-Cretaceous, and uplift and inversion in the Upper Tertiary. The difference of the clay mineralogy in the Permo-Triassic in the Ulster Basin depends upon the depositional environments, source area geology and burial history of the basin. Illite-smectite is grain coating, whereas smectite, illite-smectite, smectite-chlorite, chlorite, illite and kaolinite are the common pore-filling clay minerals in the Permo-Triassic sandstones in the Ulster Basin. Clay minerals reduced the porosity and permeability of the Permo-Triassic sandstones. KEY WORDS : Adigrat sandstone, Authigenic mineralization, Clay minerals, Diagenesis, Permo-Triassic sandstones, Reservoir characteristics Bull. Chem. Soc. Ethiop. 2008 , 22(1), 41-65.
17 citations
TL;DR: Tannery sludge derived activated carbon exhibits dye removal efficiency that is about 80-90 % of that observed with commercial coal based activated carbon as mentioned in this paper, which is the most widely used adsorbent for the removal of dyestuffs from dyeing industry effluents.
Abstract: Effective treatment of dyestuff containing textile dyeing industry effluents require advanced treatment technologies such as adsorption for the removal of dyestuffs. Powdered commercial coal based activated carbon has been the most widely used adsorbent for the removal of dyestuffs from dyeing industry effluents. As an alternative to commercial coal based activated carbon, activated carbon prepared from dried tannery sludge was used as an adsorbent for dyestuff removal from simulated textile dying industry effluent in this study. The color removal performance of tannery sludge derived activated carbon and commercial coal based activated carbon has been investigated using parameters such as adsorbent dosage, initial dye concentration, pH and temperature. It was found that tannery sludge derived activated carbon exhibits dye removal efficiency that is about 80–90 % of that observed with commercial coal based activated carbon. The amount of dye adsorbed on to tannery sludge derived activated carbon is lower compared with commercial activated carbon at equilibrium and dye adsorption capacity increased with increase of initial dye concentration and temperature, and deceasing pH. It was found that the Langmuir isotherm appears to fit the isotherm data better than the Freundlich isotherm. The leachate of heavy metals from tannery sludge derived activated carbon to the environment is very low, which are within the standard limit of industrial effluent and leachable substances. KEY WORDS: Adsorption, Tannery sludge derived activated carbon, Commercial coal based activated carbon, Adsorption isotherms, TCLP Bull. Chem. Soc. Ethiop. 2008 , 22(3), 369-378.
17 citations
TL;DR: In this paper, an extraction-spectrophotometric method for determination of nickel at sub ppm level using 2-[(mercaptophenylimino)methyl]phenol (MPMP) extractant is described.
Abstract: An extraction-spectrophotometric method for determination of nickel at sub ppm level using 2-[(2-mercaptophenylimino)methyl]phenol (MPMP) as the new extractant is described. The reagent reacts with nickel(II) at pH > 10 and form a 1:2 brown complex, which is extracted into chloroform. The complex has a maximum absorption at 421 nm with the molar absorptivity of 2.41 × 10 5 M -1 cm -1 . Beer’s law is obeyed over the range of 0.011-0.30 µg mL -1 . The Sandell’s sensitivity for 0.001 absorbance unit is 5.34 × 10 -4 µg cm -2 . The relative standard deviation at 0.018 µg mL -1 is 1.1 % (n = 8). The procedure was successfully applied to determination of nickel in wastewater and standard alloy and the accuracy was determined by recovery experiment, independent analysis by furnace-AAS, and analysis of a certified reference martial. KEY WORDS: Ni determination, Liquid-liquid extraction, Schiff bases, Spectrophotometry Bull. Chem. Soc. Ethiop. 2008 , 22(3), 323-329.
17 citations
TL;DR: In this article, the removal of chromium(VI) from aqueous solutions by Palmyra palm fruit seed carbon (PPFSC) and commercial activated carbon (CAC) was investigated.
Abstract: In this study, removal of chromium(VI) from aqueous solutions by Palmyra palm fruit seed carbon (PPFSC) and commercial activated carbon (CAC) was investigated. The metal adsorption capacity has been studied as a function of contact time, pH and carbon dosage. The adsorption yields increased with the increasing of adsorbent dosage and contact time, and subsequently reached the equilibrium. The suitability of the Freundlich and Langmuir models were also investigated for each chromium sorbent system. In order to understand the reaction mechanism, kinetic data has been studied using pseudo first order rate equation. The Lagergren’s constants were calculated for different initial concentrations of metal ions. The chromium(VI) ions could be rapidly removed from the sorbents by treatment with HCl acid and at the same time the regenerated sorbent could be used again to adsorb heavy metal ions. The suitability of this material for treatment of tannery wastewater was also examined. KEY WORDS: Adsorption; Chromium(VI) removal; Palmyra palm fruit seed carbon; Regeneration; Langmuir and Freundlich isotherm; Pseudo first order kinetics Bull. Chem. Soc. Ethiop. 2008 , 22(2), 183-196.
15 citations
TL;DR: In this article, a batch of Peanut Husk was used for removing Pb(II), Cr(δ) and Cu(II) from aqueous solution.
Abstract: Peanut husk h as been used in this work for removing Pb(II), Cr(Ш) and Cu(II) from aqueous solution. Batch adsorption studies were carried out under different pH , initial concentration of metal ions, interfering metal ions, time and temperature. Adsorption was poor in strongly acidic solution but was improved in alkaline medium and continuously increased with rise in pH. T he presence of one metal decreased the removal of the other metal ions. The adsorption processes were more akin towards second - order equation . The suitability of the adsorbent was tested by fitting the adsorption data with Langmuir and Freundlich isotherms, which gave good fits with both isotherms. For an adsorbent amount of 2 g/L and initial metal ions 10 mg/L, the maximum monolayer values of Pb(II), Cr(Ш) and Cu(II) was 4.59 mg/g, 3.34 mg/g and 2.96 mg/g. The adsorption was in the order Pb(II) > Cu(II) > Cr(Ш) . The values of the thermodynamic parameters, Δ H , Δ S and Δ G , indicated the interactions to be thermodynamically favorable. KEY WORDS: Peanut husk, Heavy metals, Sorption isotherm, Kinetics Bull. Chem. Soc. Ethiop. 2008 , 22(1), 19-26.
TL;DR: In this article, the authors reported that the Ethiopian oil shales are good to excellent source rocks types up to 34.5 % TOC values and up to 130 HC g/kg S 2.
Abstract: Inter-Trappean coal and oil shale-bearing sediments are widely distributed in the Delbi-Moye, Lalo-Sapo, Yayu, Sola, Chida, Chilga, Mush Valley, Wuchale and Nejo Basins. Coal and oil shale-bearing sediments were deposited in fluvio-lacustrine and paludal depositional environments. The Ethiopian oil shales reach a maximum thickness of 60 m, and contain mixtures of algal, herbaceous and higher plant taxa. Type II and I kerogen dominated the studied oil shales. Pyrolysis data revealed that the Ethiopian oil shales are good to excellent source rocks types up to 34.5 % TOC values and up to 130 HC g/kg S 2 . A total of about 653,000,000 - 1,000,000,000 tones of oil shale reserve registered in the country. The coal and coal-bearing sediments attain a maximum thickness of 4 m and 278 m, respectively. Proximate analysis and calorific value data show that the Ethiopian coals fall under the soft coal series (lignite to bituminous coal), and genetically classified under humic, sapropelic and mixed coals. A total of about 297,000,000 tones of coal reserve registered in the country. The Permian Bokh Shale, Oxfordian-Bathonian Hamanlei Limestones, Kimmeridgian Urandab Shale are potential organic-rich source rocks. The Permian Calub sandstone, Triassic-Liassic Adigrat sandstone and Oxfordian-Bathonian Hamanlei carbonates are reservoirs in the Ogaden and Blue Nile Basins. 2.7 TCF (76 x 10 9 m 3 ) sulfur-free gas and 1817 x 10 6 tons condensate reserves are estimated in the Calub field. About 1.3 TCF gas deposit is also encountered in Hilala field. The Blue Nile Basin is one of the potential basins for hydrocarbon exploration. The presence of mature source rocks and oil seepage in the Blue Nile Basin is clue for the generation of hydrocarbon in the basin. The Gambella Basin is the southern extension of the petroliferous Sudan Interior Basins, and could be one of the potential basins for oil and gas deposits. KEY WORDS: Coal, Energy, Ethiopia, Fossil fuel, Oil shale, Oil and gas Bull. Chem. Soc. Ethiop. 2008 , 22(1), 67-84.
TL;DR: The Fe(III), Ru(III, Rh(III) and Cr(III ) complexes of 4-amino-N-(2-pyrimidinyl)benzene sulfonamide (sulfadiazine) have been synthesized and characterized by elemental analysis, electronic and IR spectroscopy, conductance and room temperature magnetic susceptibility measurements as discussed by the authors.
Abstract: The Fe(III), Ru(III), Rh(III), and Cr(III) complexes of 4-amino-N-(2-pyrimidinyl)benzene sulfonamide (sulfadiazine) have been synthesized and characterized by elemental analysis, electronic and IR spectroscopy, conductance and room temperature magnetic susceptibility measurements. Sulfadiazine acts as a bidentate ligand through the sulfonamido and the pyrimidinic N-atoms. The compounds are non-electrolytes and the electronic spectra are consistent with the proposed octahedral geometry around the metal ions. The complexes were tested for in vitro activity against cultures of the resistant strains of Plasmodium falciparum , tripamastigotes T . b . rhodesiense and amastigotes L . donovani to determine their antiprotozoal activities. The Fe(III) complex is more active than the other complexes against the parasitic protozoa. KEY WORDS: Metal complexes, Sulfadiazine, Parasites, Protozoa, Drug resistance Bull. Chem. Soc. Ethiop. 2008 , 22(2), 261-268.
TL;DR: In this article, the authors investigated the dispersion of contaminated Zn, Ni, Cr, Hg, and Pb within the soil profile and found significant levels of contamination were found in view of elevated levels of these metals above background concentrations in control sites.
Abstract: Growing concern about reclamation of auto-repair workshop areas for residential and agricultural purposes makes risk assessment of heavy metal contamination of the study area imperative. In addition, the study is aimed at ascertaining the dispersion of contaminated Zn, Ni, Cr, Hg, and Pb within the soil profile. A total of 75 soil samples from auto-repair workshops and 18 soil samples from control sites were collected. Significant levels of contamination were found in view of elevated levels of these metals above background concentrations in control sites. Average topsoil metal concentrations (0-10 cm) in auto-repair workshop areas were: Zn 0.90 ± 0.5, Ni 11.5 ± 3.3, Cr 5.3 ± 2.3, Hg 9.4 ± 4.6 and Pb 133 ± 66 mg/kg. Lead was the most significant contaminants, and the degree of contamination was highest for Pb followed by Hg. The detailed levels of total metal contamination for Pb and Hg exceeded international thresholds for agricultural use. Enrichment factor within the soil profile metals were Zn 3.37, Ni 3.38, Cr 6.22, Hg 14.5 and Pb 21.1. The enrichment factor reflects the ratio of average concentration at a particular sampling location to average concentration at control sites. The general trend of dispersion of metal contaminants within the soil profile studied is Pb >> Ni > Hg > Cr >>Zn. KEY WORDS: Auto-repair, Lead, Mercury, Soil, Heavy metals, Dispersion Bull. Chem. Soc. Ethiop. 2008 , 22(3), 339-348.
TL;DR: An efficient method for separating chlorophyll from spinach leaves by column chromatography and solvent extraction techniques has been developed as discussed by the authors, which has been confirmed by UV-Vis, IR and mass spectrometry.
Abstract: An efficient method for separating chlorophyll a from spinach leaves by column chromatography and solvent extraction techniques has been developed. The purity and identity of the chlorophyll a have been confirmed by UV-Vis, IR and mass spectrometry. Yields from 100 g of freeze-dried spinach were 23 – 24 mg of chlorophyll a . KEY WORDS: Chlorophyll a , Spinach leaves, Separation, Column chromatography, Solvent extraction, Pheophytin a Bull. Chem. Soc. Ethiop. 2008 , 22(2), 301-304.
TL;DR: In this paper, an activated carbon modified method was used for preconcentration and determination of copper content in real samples such as tap water, wastewater and a synthetic water sample by flame atomic absorption spectrometry.
Abstract: Activated carbon modified method was used for the preconcentration and determination of copper content in real samples such as tap water, wastewater and a synthetic water sample by flame atomic absorption spectrometry. The copper(II) was adsorbed quantitatively on activated carbon due to its complexation with ethyl-2-quinolyl-β( p -carboxyphenyl hydrazone)dioxo propionate (EQCPDP). The adsorbed copper(II) ion on solid phase was eluted quantitatively by using nitric acid. The important parameters such as pH, amount of carrier, flow rate, amount of activated carbon and type and concentration of eluting agent for obtaining maximum recovery were optimized. The method at optimum conditions gives linear concentration range of 0.05-1.0 μ g mL -1 of copper(II) with correlation coefficient of 0.9994 and the detection limit of 0.99 ng mL -1 . The preconcentration leads to enrichment factor of 175 and break through volume of 1750 mL. The method has good tolerance limit of interfering ions and selectivity and it has been successfully applied for determination of copper content in real sample such as blood, wastewater and river sample. KEY WORDS: Copper(II), Solid phase extraction, Activated carbon, Flame atomic absorption spectrometry Bull. Chem. Soc. Ethiop. 2008 , 22(3), 331-338.
TL;DR: In this article, the thermodynamics of ion exchange equilibrium for uni-univalent Cl - /I -, Cl -/Br -, and uni -divalent Cl- /SO 4 2 O 4 2 - reaction systems was carried out using ion exchange resin Duolite A-102 D. The equilibrium constant was calculated by taking into account the activity coefficient of ions both in solution as well as in the resin phase.
Abstract: The study on thermodynamics of ion exchange equilibrium for uni-univalent Cl - /I - , Cl - /Br - , and uni-divalent Cl - /SO 4 2- , Cl - /C 2 O 4 2- reaction systems was carried out using ion exchange resin Duolite A-102 D. The equilibrium constant K was calculated by taking into account the activity coefficient of ions both in solution as well as in the resin phase. The K values calculated for uni-univalent and uni-divalent anion exchange reaction systems was observed to increase with rise in temperature, indicating the endothermic exchange reactions having enthalpy values of 13.7, 38.0, 23.9, 22.9 kJ/mol, respectively. KEY WORDS: Duolite A-102 D ion exchange resin, Equilibrium constant, Endothermic ion exchange reaction, Enthalpy, Thermodynamic study Bull. Chem. Soc. Ethiop. 2008 , 22(1), 107-114.
TL;DR: In this article, an ab initio two-body potential and a function correcting for 3-body effects for Cd(II)-water system are constructed by means of molecular dynamics simulations.
Abstract: An ab initio two-body potential and a function correcting for 3-body effects for Cd(II)-water system are constructed. The hydration structure of Cd(II) has been studied by means of molecular dynamics simulations. The inclusion of the three-body correction was found to be crucial for the description of the system, and results thus obtained are in good agreement with experimental values. Radial distribution functions, coordination number distributions, and various angular distributions have been used to discuss details of the hydration structure, together with bond lengths and bond angles of the water molecules in the first hydration shell. The Cd(II) is found 6-fold coordinated. Water molecules in the first hydration shell are shown to be polarized compared to the gas-phase structures. Umbrella-sampling molecular dynamics simulations were performed to investigate the water exchange reaction of Cd(II) ion in aqueous solution. The water-exchange rate constant at 298 K is estimated by the transition state theory to be 4.9 x 10 8 s -1 , assuming a transmission coefficient of unity. KEY WORDS: Molecular dynamics, Umbrella sampling, Hydration structure, Cd(II), Water exchange, Three-body corrections Bull. Chem. Soc. Ethiop. 2008 , 22(3), 423-432.
TL;DR: In this paper, a tentative mechanism has been proposed for photocatalytic degradation of xanthene dyes using anthracene semiconductor immobilized on polyethylene films, where the effect of various parameters like pH, concentration of dyes, amount of semiconductor and light intensity have been studied on the rate of reaction.
Abstract: Photocatalytic degradation of eosin and erythrosin-B (xanthene dyes) has been carried out using anthracene semiconductor immobilized on polyethylene films. Effect of various parameters like pH, concentration of dyes, amount of semiconductor and light intensity have been studied on the rate of reaction. Various control experiments were carried out which indicated that semiconductor anthracene played a key role in photocatalytic degradation of dyes. A suitable tentative mechanism has been proposed for photocatalytic degradation of dyes. KEY WORDS: Photocatalytic, Degradation, Xanthene dyes, Immobilized anthracene Bull. Chem. Soc. Ethiop. 2008 , 22(3), 361-368.
TL;DR: In this article, chemical and biochemical studies of Maerua subcordata plant juice extract were carried out to establish whether the material that settled as a result of clarification had minerals, protein and/or polysaccharides.
Abstract: This paper reports some findings of chemical as well as biochemical studies of Maerua subcordata plant juice extract The studies include: chemical composition of the juice such as mineral contents, protein and polysaccharide contents These tests were carried out both in the juice extracts and in the “flocs” The latter samples were analyzed to establish whether the material that settled as a result of clarification had minerals, protein and/or polysaccharides While there were no significant amounts of minerals found in the juice or in the flocs, there were significant amounts of polysaccharides in the juice as well as in the flocs However it was found that there were insignificant amounts of proteins in the settled flocs This was indication that polysaccharides in the juice were precipitated along with the sediments present in water Further biochemical experiments on the identity of polysaccharides which apparently aided flocculation indicated that they were of branched type, amylopectin The paper attempts to explain the mechanism of sediments settling as aided by the plant juice components KEY WORDS: Turbid surface water treatment, Coagulation, Flocculation, Maerua subcordata plant, Amylopectin polysaccharide Bull Chem Soc Ethiop 2008 , 22(1), 143-148
TL;DR: In this paper, the reaction of 1-cyclopropyl-6-fluoro-4-oxo-7-(piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid derivatives with thiazole/benzothiazole diazonium chloride afforded piperazine substituted ciprofloxacin derivative.
Abstract: Reaction of 1-cyclopropyl-6-fluoro-4-oxo-7-(piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid (ciprofloxacin) with thiazole/benzothiazole diazonium chloride afforded piperazine substituted ciprofloxacin derivative. The acid part of these derivatives was further condensed with various β-diketones to get 1-cyclopropyl-6-fluoro-4-oxo-7-(4-(thiazol-2-yldiazenyl)piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid derivatives ( 5a-e ) and 7-(4-(benzo[d]thiazol-2-yldiazenyl)piperazin-1-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid derivatives ( 5f-j ). Structures of these compounds were established on the basis of spectral studies. KEY WORDS: Ciprofloxacin, Thiazole, Benzothiazole, β- Diketone Bull. Chem. Soc. Ethiop. 2008 , 22(3), 459-464.
TL;DR: In this paper, malachite green (MG) was used as a bioprobe to determine heparin concentration by linear sweep voltammetry on the dropping mercury working electrode (DME).
Abstract: In this paper malachite green (MG) was used as a bioprobe to determine heparin concentration by linear sweep voltammetry on the dropping mercury working electrode (DME). In Britton-Robinson (B-R) buffer solution of pH 1.5, MG had a well-defined second order derivative linear sweep voltammetric reductive peak at –0.618 V (vs. SCE). After the addition of heparin into the MG solution, the reductive peak current decreased apparently without the movement of peak potential. Based on the difference of the peak current, a new voltammetric method for the determination of heparin was established. The conditions for the binding reaction and the electrochemical detection were optimized. Under the selected experimental conditions the difference of peak current was directly proportional to the concentration of heparin in the range from 0.3 to 10.0 mg/L with the linear regression equation as ∆ip″ (nA) = 360.19 C (mg/L) + 178.88 ( n = 15, γ = 0.998) and the detection limit as 0.28 mg/L (3 σ ). The effects of coexisting substances such as metal ions, amino acids on the determination of heparin were investigated and the results showed that this method had good selectivity. This method was further applied to determine the heparin content in heparin sodium injection samples with satisfactory results and good recovery. The stoichiometry of the biocomplex was calculated by the electrochemical method and the binding mechanism was further discussed. KEY WORDS: Heparin, Malachite green, Voltammetry, Binding reaction Bull. Chem. Soc. Ethiop. 2008 , 22(2), 165-172.
TL;DR: In this paper, the electrochemical behavior of L-cysteic acid was studied at the surface of 1-[4-(ferrocenyl-ethynyl)phenyl]-1-ethanone modified carbon paste electrode (4FEPEMCPE) in aqueous media using cyclic voltammetry and double step potential chronoamperometry.
Abstract: The electrochemical behaviour of L-cysteic acid was studied at the surface of 1-[4-(ferrocenyl-ethynyl)phenyl]-1-ethanone modified carbon paste electrode (4FEPEMCPE) in aqueous media using cyclic voltammetry and double step potential chronoamperometry. It has been found, that under optimum condition (pH 7.00) in cyclic voltammetry, the oxidation of L-cysteic acid at the surface of 4FEPEMCPE is occurred at a potential about 220 mV less positive than that an unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient, α, and catalytic reaction rate constant, K / h , were also determined using electrochemical approaches. The electrocatalytic oxidation peak current of L-cysteic acid showed a linear dependent on the L-cysteic acid concentration and linear calibration curves were obtained in the ranges of 9 × 10 -5 - 6.2 × 10 -3 M and 2.0 × 10 -7 - 1.17 × 10 -5 M of L-cysteic acid concentration with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods, respectively. The detection limits (3σ) were determined equal to 2.3 × 10 -5 M and 8.7 × 10 -8 M by CV and DPV methods. This method was also examined as a selective, simple and precise new method for voltammetric determination of L-cysteic acid in serum of patient's blood with migraine disease. KEY WORDS: 1-[4-(Ferrocenyl-ethynyl)phenyl]-1-ethanone, L-Cysteic acid, Electrocatalysis, Cyclic voltammetry, Differential pulse voltammetry, Chronoamperometry Bull. Chem. Soc. Ethiop. 2008 , 22(2), 173-182.
TL;DR: In this article, the molecular structures of 1,4-dithiine and S-oxygenated derivatives are studied using B3LYP/6-311++G** level of theory.
Abstract: The molecular structures of 1,4-dithiine and S-oxygenated derivatives are studied using B3LYP/6-311++G** level of theory. These compounds have 8 π -electrons in the ring. This led to stabilization of non-planar conformation. DFT calculations show that 1,4-dithiine, C 4 H 4 SS, 1,4-dithiine-1-oxide, C 4 H 4 SOS, 1,4-dithiine-1,4-dioxide, C 4 H 4 SOSO and 1,4-dithiine-1,1,4-trioxide, C 4 H 4 SO 2 SO; have boat conformation. 1,4-dithiine-1,1-dioxide, C 4 H 4 SO 2 S, have a shadow boat conformation. 1,4-dithiine-1,1,4,4-tetraoxide, C 4 H 4 SO 2 SO 2 , have a planar conformation. KEY WORDS: DFT calculation, 1,4-Dithiine, S-Oxygenated, Molecular structure Bull. Chem. Soc. Ethiop. 2008 , 22(3), 465-468.
Abstract: Two simple, sensitive and rapid methods are described for the determination pantoprazole sodium sesqui hydrate (PNT) in bulk drug and in formulations using N-bromosuccinimide (NBS) as the oxidimetric reagent. The methods involve the addition of a known excess of NBS to PNT in HCl medium followed by estimation of the unreacted oxidant by two reaction schemes involving the use of iron(II) and thiocyanate (method A) or tiron (method B). In both methods, the absorbance is found to decrease linearly with PNT concentration. Beer’s law is obeyed over the ranges 0.25-3.5 and 1-15 µg mL -1 for method A and method B, respectively. The calculated molar absorptivity values are 1.4 × 10 5 and 2.5 × 10 4 L mol -1 cm -1 for method A and method B, respectively. The limit of detection (LOD) and quantification (LOQ) are also reported for both methods. The RSD values for intra-day and inter-day precision studies were less than 2.5 and 3.0 %, respectively. Both the methods were applied to the determination of PNT in dosage forms and the results were satisfactory, and were comparable with those obtained by the reference method. The accuracy and reliability of the proposed methods were further ascertained by recoveries studies, and the recoveries of the spiked drug ranged between 98.5 and 102.5 %. KEY WORDS: Pantoprazole sodium, Determination, N-bromosuccinimide, Complexation reactions, Pharmaceuticals Bull. Chem. Soc. Ethiop. 2008 , 22(1), 135-141.
TL;DR: In this paper, N-(2-nitro)-benzilidene-3-hydrazino quinoxaline-2-one (NBHQO) has been synthesized and characterized by elemental analysis, conductance, thermal, spectral and magnetic data.
Abstract: Cr(III), Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) complexes of N-(2-nitro)-benzilidene-3-hydrazino quinoxaline-2-one (NBHQO) have been synthesized and characterized by elemental analysis, conductance, thermal, spectral and magnetic data. NBHQO acts as a bidentate ON donor in all the complexes except in Ni(II) complex in which it acts as a tridentate ONO donor. Octahedral geometries have been proposed for all the complexes except for Cu(II) complex to which the square planar geometry is assigned. KEY WORDS: Metal c omplexes, N-(2-nitro)-benzilidene-3-hydrazino quinoxaline-2-one, ON donor Bull. Chem. Soc. Ethiop. 2008 , 22(3), 385-390.
TL;DR: In this paper, the authors show that PCl 5 can efficiently catalyze the condensation of indoles with aldehydes as well as ketones at room temperature to afford bis(indolyl)methanes and di-bis(inolyl)-methane in high yields and short reaction times.
Abstract: Phosphorus pentachloride (PCl 5 ) can efficiently catalyze the condensation of indoles with aldehydes as well as ketones at room temperature to afford bis(indolyl)methanes and di-bis(indolyl)methanes in high yields and short reaction times. KEY WORDS: PCl 5 , bis(Indolyl)methane, di-bis(Indolyl)methane, Indole, Aldehyde, Ketone Bull. Chem. Soc. Ethiop. 2008 , 22(3), 453-458.
TL;DR: In this article, the thermodynamics of ion exchange equilibrium for uni-univalent Cl - /I -, Cl -/Br -, and uni -divalent Cl- /SO 4 2 O 4 2-, Cl − /C 2 O4 2 2 ) reaction systems were carried out using ion exchange resin Indion FF-IP.
Abstract: The study on thermodynamics of ion exchange equilibrium for uni-univalent Cl - /I - , Cl - /Br - , and uni-divalent Cl - /SO 4 2- , Cl - /C 2 O 4 2- reaction systems was carried out using ion exchange resin Indion FF-IP. The equilibrium constant K was calculated by taking into account the activity coefficient of ions both in solution as well as in the resin phase. For uni-univalent ion exchange reaction systems, the equilibrium constant K’ were also calculated by considering mole fraction of ions in the resin phase. The K values calculated for uni-univalent and uni-divalent anion exchange reaction systems were observed to increase with rise in temperature, indicating the endothermic exchange reactions having enthalpy values of 22.45, 28.57, 17.84, 15.97 kJ/mol, respectively. KEY WORDS: Ion exchange equilibrium, Equilibrium constant in standard state, Apparent equilibrium constant, Enthalpy, Endothermic reaction Bull. Chem. Soc. Ethiop. 2008 , 22(3), 415-421.
TL;DR: In this article, the stoichiometry and stability constants of the ion-association complexes were determined using Benesi-Hildebrand method and the stochometry was confirmed by Job's continuous variation method.
Abstract: With thiocyanate, zinc(II), cobalt(II) and copper(II) ions form stable anion, [M(SCN) 4 ] 2- . This anion in turn with methylene blue (MB + ) forms ion-pair of the type MB 2 [M(SCN) 4 ] and turns methylene blue to violet. The stoichiometry and stability constants of the ion-association complexes were determined using Benesi-Hildebrand method and the stoichiometry was confirmed by Job’s continuous variation method. The kinetics of formation of ternary complexes was studied using stopped-flow technique. The equilibrium studies showed that the stability of ternary complexes increased in the order Co(II) > Cu(II) > Zn(II) and the formation rate constants increased in the order, Cu(II) > Zn(II) > Co(II). The relative stabilities indicate that cobalt is preferred to other two metals in the speciation of ternary complexes comparable with similar complexes in biosystems. This study also provides a method for the spectrophotometric determination of Co(II) and Zn(II) ions at nanogram levels at 25 o C and an ionic strength of 0.15 M. KEY WORDS: Ion-association complex, Kinetics, Zinc, Cobalt, Methylene blue, Thiocyanate Bull. Chem. Soc. Ethiop. 2008 , 22(1), 85-91.
TL;DR: In this paper, a method that involves analysis of bovine liver by slurry nebulization and ICP-OES has been developed, which permits rapid and accurate determination of Cu, Fe, Mg, Mn, Zn and Zn.
Abstract: A method that involves analysis of bovine liver by slurry nebulization and ICP-OES has been developed. This method permits rapid and accurate determination of Cu, Fe, Mg, Mn and Zn in bovine liver. Aliquots of freeze-dried and powdered bovine liver sample were dispersed in 2.0 M HNO 3 and sonicated to homogenize the resulting slurries. Bovine liver samples were also microwave digested or subjected to aqueous extraction for comparison of analytical results. Concentrations of Cu, Fe, Mg, Mn and Zn in aqueous slurries, the digests, and aqueous extracts were determined by the ICP-OES using external calibration curves. A student’s t -test showed that the results obtained using the slurry method were in good agreement at 95 % confidence level (CL) with those of microwave digestion or aqueous extraction techniques, except for Fe. To check the accuracy and precision of the slurry method, a bovine liver CRM was analyzed and good agreement was achieved with the certified values at 95 % CL. The results demonstrate inefficiency of aqueous extraction technique for complete removal of Fe in bovine liver sample. KEY WORDS: Bovine liver, ICP-OES, Slurry nebulization, Cu, Fe, Mg, Mn, Zn Bull. Chem. Soc. Ethiop. 2008 , 22(3), 313-321.