Isolation of chlorophyll a from spinach leaves

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

HYDRAZIDE SCHIFF BASES OF ACETYLACETONATE METAL COMPLEXES: SYNTHESIS, SPECTROSCOPIC AND BIOLOGICAL STUDIES

Objective: The study was focused on the synthesis and spectroscopic studies of metal acetylacetonates and their complexes using bidentate Schiff-base ligands (NO), evaluation of their in-vitro antibacterial potentials against pathogenic microorganism.Methods: Acetylacetonate salts of Cobalt(II), Manganese(II) and Magnesium(II) were prepared by reacting their metal hydroxides with acetylacetone. The metal complexes of N'-{(E)-[4-(diethylamino)-2-hydroxyphenyl]methylidene}-4-nitrobenzohydrazide (HL1), N'-{(E)-[4-(diethylamino)-2-hydroxyphenyl]methylidene}-4-methoxybenzohydrazide (HL2) obtained from the condensation reaction of 4-(diethylamino)-2-hydroxybenzaldehyde and 4-nitrobenzohydrazide/ or 4-methoxybenzohydrazide. The synthesized compounds were characterized by fourier transform infrared spectroscopy (FT-IR), proton and carbon-13 nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA). The compounds were screened for their antimicrobial properties against a list of Gram-positive bacterial strains.Results: The FT-IR spectra revealed that the Schiff bases acts as bidentate chelating ligand via nitrogen of the azomethine and phenolic oxygen atoms. NMR reveal the presence of azomethine (HC=N) and aromatic hydrogens at expected chemical shifts confirming the formation of the Schiff base ligands. Thermal decomposition behaviour was studied by thermogravimetry revealing stability up to 260 °C. The compounds were evaluated for their antibacterial potentials against Staphylococcus aureus and Enterococcus faecalis. The manganese acetylacetonato(N'-{(E)-[4-(diethylamino)-2-hydroxyphenyl]methylidene}-4-methoxybenzohydrazide: Mn(acac)(L2) exhibited antimicrobial activities against both Enterococcus faecalis and Staphylococcus aureus with a minimum inhibitory concentration (MIC) of 398.0 μg/mL.Conclusion: The prepared compounds showed no inhibition against the selected pathogenic microorganisms except for Mn(acac)(L2) Standard antibacterial compounds: ampicillin and ciprofloxacin were used as positive control. The antibacterial activity of the compound depends on the kind of substituent on the benzo hydrazide rings at the para position, thereby suggesting the compound as promising chemotherapeutic agents for further structural optimization.Â

Solid State NMR Characterization and Adsorption Properties of Lignocellulose-Clinoptilolite Composites Prepared with Siloxanes Coupling Agents

This study reports the preparation of lignocellulose-clinoptilolite composites by means of N-terminated siloxanes as coupling agents, after acid hydrolysis. Reactions were carried out in the presence of dibutyltin dilaurate as catalyst by reacting lignocellulose modified with the coupling agents and clinoptilolite at 140 °C inDMFunder nitrogen atmosphere. The light in weight and fluffy composites obtained were characterized by FT-IR, XRD, TGA, SEM and Solid State NMR. Results depicted possible chemical interactions between the two materials (lignocellulose and clinoptilolite). Used as adsorbents, the composites showed to be good candidates for the removal of used motor oil fromaqueous solution, withupto 92mg g–1 of chemical oxygen demand removed.KEYWORDS Lignocellulose, clinoptilolite, chemical modification, composites, solid state NMR, used motor oil

An Improvement of Load Flow Solution for Power System Networks using Evolutionary-Swarm Intelligence Optimizers

Load flow report which reveals the existing state of the power system network under steady operating conditions, subject to certain constraints is being bedeviled by issues of accuracy and convergence. In this research, five AI-based load flow solutions classified under evolutionary-swarm intelligence optimizers are deployed for power flow studies in the 330kV, 34-bus, 38-branch section of the Nigerian transmission grid. The evolutionary-swarm optimizers used in this research consist of one evolutionary algorithm and four swarm intelligence algorithms namely; biogeography-based optimization (BBO), particle swarm optimization (PSO), spider monkey optimization (SMO), artificial bee colony optimization (ABCO) and ant colony optimization (ACO). BBO as a sole evolutionary algorithm is being configured alongside four swarm intelligence optimizers for an optimal power flow solution with the aim of performance evaluation through physical and statistical means. Assessment report upon application of these standalone algorithms on the 330kV Nigerian grid under two (accuracy and convergence) metrics produced PSO and ACO as the best-performed algorithms. Three test cases (scenarios) were adopted based on the number of iterations (100, 500, and 1000) for proper assessment of the algorithms and the results produced were validated using mean average percentage error (MAPE) with values of voltage profile created by each solution algorithm in line with the IEEE voltage regulatory standards. All algorithms proved to be good load flow solvers with distinct levels of precision and speed. While PSO and SMO produced the best and worst results for accuracy with MAPE values of 3.11% and 36.62%, ACO and PSO produced the best and worst results for convergence (computational speed) after 65 and 530 average number of iterations. Since accuracy supersedes speed from scientific considerations, PSO is the overall winner and should be cascaded with ACO for an automated hybrid swarm intelligence load flow model in future studies. Future research should consider hybridizing ACO and PSO for a more computationally efficient solution model

Synthesis and Oxidation of Cobalt(II) Pheophytin-a Complex

Abstract: The mechanism of oxidation of natural pheophytin-a incorporated with cobalt as the central metal ion has been investigated. Natural pheophytin-a extracted from spinach was metallated with cobalt(II) to form the complex, cobalt(II) pheophytin-a [Cophe]. The complex was characterized by Ultraviolet and Visible, Fourier Transform Infrared and Electrospray ion Mass Spectroscopy. The synthesis of cobalt(II) pheophytin-a was carried out and the effect of the substitution on the chlorophyll macrocycle was studied by the reaction of hexaaquachromium(III) cation. The presence of cobalt as the central metal ion increases the energies of the chlorophyll main absorption transitions. The oxidation of the cobalt(II) pheophytin-a, [Cophe] by hexaaquachromium(III) cation in dilute hydrochloric acid has been studied and found to follow first-order kinetics. Rate constants for the oxidation reaction at 313, 322.8 and 332.9 K were found to be 5.4x10 -5 , 1.8x10 -4 and 5.9x10 -4 /s respectively. An outer-sphere mechanism has been proposed for the oxidation of cobalt(II) pheophytin-a

Laser modification of graphene oxide layers

The effect of linearly polarized laser irradiation with various energy densities was successfully used for reduction of graphene oxide (GO). The ion beam analytical methods (RBS, ERDA) were used to follow the elemental composition which is expected as the consequence of GO reduction. The chemical composition analysis was accompanied by structural study showing changed functionalities in the irradiated GO foils using spectroscopy techniques including XPS, FTIR and Raman spectroscopy. The AFM was employed to identify the surface morphology and electric properties evolution were subsequently studied using standard two point method measurement. The used analytical methods report on reduction of irradiated graphene oxide on the surface and the decrease of surface resistivity as a growing function of the laser beam energy density

Extraction, isolation and physicochemical studies of natural pheophytin complexes

Thesis (D.Phil) North-West University, Mafikeng Campus, 2005A simple, rapid and efficient method for the extraction and purification of chlorophyll-a from plant sources has been developed. And with it, a new method for the ·extraction of chlorophyll in winter, which has been previously problematic, has been developed. The methods are summarized in flow diagrams showing the elimination of carotene and xanthophylls. The chlorophyll-a isolated has been demetallated to obtain pheophytin-a that in tum has been complexed with cobalt(II), copper(II), zinc, nickel(II) and chromium(Ill) ions. The resulting metal pheophytin complexes, chlorophyll-a and pheophytin-a have been fully characterized by ultraviolet-visible and Fourier transform infrared spectroscopies, electrospray ion mass spectrometry and elemental analysis. For the first time, the kinetics of the oxidation of cobalt(II) pheophytin-a by chromium(III) has been followed spectrophotometrically at temperatures ranging from 313 to 333 K. The reaction has been found to be first order in the concentration of the hexaaquachromium(III) cation. The oxidation-reduction mechanism proposed for the reaction is an outer-sphere electron tunnelling mechanism. The ease of demetallation and complexation of chlorophyll-a has highlighted the problem caused by acidity and the presence of these metal ions in soils, on the chlorophyll content of leaves.Doctora

Morphological Characterization of Soot from the Atmospheric Combustion of Kerosene

Kerosene has been used as a precursor for the production of carbon nanomaterial without a catalyst precursor. Nanomaterials formed in the process have been analysed by Raman, Scanning electron microscope (SEM), x-Ray diffraction (XRD) and by Energy dispersive spectroscopy (EDS). Carbon nanomaterial produced show the morphology of carbon nanospheres with diameters of about 0.3 µm

A Comparative Study of Carbon Nanotubes Synthesized from Co/Zn/Al and Fe/Ni/Al Catalyst

The catalyst systems Fe/Ni/Al and Co/Zn/Al were synthesized and used in the synthesis of carbon nanotubes. The carbon nanotubes produced were characterized by Field Emission Scanning Electron Microscope (FE-SEM), Energy Dispersive x-ray Spectroscopy (EDS), Raman spectroscopy, Thermogravimetric Analysis (TGA) and Transmission Electron Microscope (TEM). A comparison of the morphological profile of the carbon nanotubes produced from these catalysts indicates the catalyst system Fe/Ni/Al to have produced higher quality carbon nanotubes than the catalyst system Co/Zn/Al