Department of Chemistry
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Item Aflatoxin Levels In Groundnut And Maize Crops And Risk Assessment Based On Consumption In Ghana(University of Ghana, 2023-06) Opoku, R.B.Aflatoxins are a type of mycotoxins that contribute to about 25% loss of annual crop production worldwide. Significant human exposure to aflatoxins is associated with detrimental health implications. Thus, the extensive presence of aflatoxins in food and feed poses a huge threat to public health in many countries in Africa including Ghana. Staples foods such as groundnut and maize are highly susceptible to aflatoxin contamination. Despite their broad exposure, research on aflatoxins in food and exposure to the population is limited and mostly restricted to exported foods. This exposes millions of people to potentially acute or chronic amounts of aflatoxins. In this work, the concentrations of aflatoxins AFB1, AFB2, AFG1, and AFG2 level in 303 samples, including 165 samples of maize and 138 samples of groundnut, obtained from homes, markets, and storage centres in eight regions of Ghana was carried out. The samples were analyzed by extracting aflatoxin with methanol/water, cleaned up on an immunoaffinity column and analysed using Reverse-Phase High-Performance Liquid Chromatography (RP-HPLC) with fluorescence detection. Based on the data obtained, aflatoxins were quantified in 80.6% of the maize samples with levels ranging from 0.20 to 1129.7 μg/kg. The quantified levels of aflatoxins in groundnut samples ranged from 0.20 to 1242.9 μg/kg, with an occurrence of 73.9% in samples. Total aflatoxins were present in more than 50% of maize and 26% of groundnut samples at concentrations that exceeded the Ghanaian standard of 10 μg/kg. The study suggests that the Ghanaian population may be exposed to aflatoxins at significant concentrations, given that, the values obtained in this study represent some of the highest levels and prevalence recorded in the country. This study provides useful data for policy decision-making on the prioritization of aflatoxin as a significant food safety concern in Ghana.Item Synthesis And Characterization Of Azo Dyes As Sensitizers For Possible Application In Dye-Sensitized Solar Cells (DSSCS)(University Of Ghana, 2021-09) Essah, B.O.K.Eight azo dyes were synthesized, purified and characterized. The Stuart Melting Point Apparatus was used to measure the melting point of the dyes, UV-Vis spectroscopy was used to measure the absorbance in the UV-Vis region, FT-IR Spectroscopy was used to determine the chemical bonds and composition of the azo dyes. The 1H NMR and 13C NMR were used to successfully elucidate the chemical structures of the synthesized azo dyes (DYE 1, DYE 2, DYE 3, DYE 4, DYE 5, DYE 6, DYE 7 and DYE 8). The Cyclic voltammetry was used to characterize the electrochemical behaviour of the azo dyes as sensitizers for application in Dye Sensitized Solar Cells (DSSCs). The results of the instrumentational analysis of each synthesized azo dye were compared to that of the industrial standard, inorganic ruthenizer 535-bisTBA (N719) dye. The photochemical optical band gap (Eg) calculated for the azo dyes ranged from 1.969 eV to 2.886 eV. The dye sensitizers showed an extrapolated electrochemical oxidation potential were between 0.28 eV to 0.66 eV with DYE 1 and DYE 8 offering the most efficient potential difference to remove an electron from their molecular orbitals. The optical band gaps of the dyes were between 1.969 eV and 2.886 eV as compared to literature value of 1.91 eV of the standard N719 dye. The low Eg of DYE 1, DYE 2, DYE 6 and DYE 7 suggest that the distances between their HOMO and LUMO levels is such that the energy in the visible region is enough to cause electron promotion from their valence band into their conduction bands. The calculated LUMO values obtained were -3.149 eV, -3.204 eV, -3.43 eV for DYE 6, DYE 7 and the standard N719 dye respectively. The DYE 3 has the highest LUMO energy level of -2.313 eV. The difference in the LUMO and the HOMO indicates that the electrochemical band gap of the standard N719 dye is 1.909 eV, which is the least followed by 1.97eV band gap energy for DYE 1. The electrochemical band gap of DYE 7 and DYE 6 were 2.81 eV and 2.28 eV respectively which were the second and third least energy values. These values were closer to that of the standard N719 dye. Out of the eight azo dyes studied, the DYE 1, DYE 6 and DYE 7 showed the best DSSCs sensitizer abilities although they were still less than that of the industrial dye.Item Soil Quality Of Selected Farms In Asesewa In The Eastern Region Of Ghana(University Of Ghana, 2021-09) Adu, E.T.Increasing demand for food supply, coupled with the financial needs of smallholder farmers has triggered the use of farm management practices that threaten the quality of agricultural soils. These practices include annual bushfire for clearing the land, yearly plowing and the indiscriminate application of pesticides. These practices have the propensity of reducing the soil quality. Soil quality indicators provide essential knowledge on the capacity of soils to function within the ecosystem and support plant growth. This work studied the soil quality status of farms from the Upper Manya Krobo District, Asesewa by measuring their physical, chemical and biological indicators. The results for the chemical indicators show strongly acidic to neutral soils with pH range of 4.88-7.26. Electrical conductivity measurements were low in all the soils 0.043-0.317 (dS /m) with soils showing high percentage organic matter between 2.70%-7.90 %. The number of exchangeable sites for cations (cation exchange capacity) was between 10.77-33.31(cmol(+)/Kg). For exchangeable bases, Calcium was 3.21-11.56 (cmolc/kg) , Magnesium was in a range of 0.69-3.12(cmolc/kg), 0.63-1.27(cmolc/kg) for Potassium and 0.27-0.57(cmolc/kg) for Sodium. The biological indicators show a total microbial population in the soils for serial dilutions of 10-4 and 10-5for bacteria. Bacterial population for sixteen farms was within the acceptable range in pesticide treated soils however, they were not present in population that can support microbial activities and processes enough in the soil. A great number of fungal isolates in the soil was not inhibited by pesticide application especially, Streptomyces sp. compared to control groups.Item Anaemia In Pregnancy And Associated Factors: A Cross- Sectional Study Of Antenatal Attendants At Mamobi General Hospital(University of Ghana, 2019-05) Ousman, F.Background: Anaemia is a health problem that is associated with a decrease in the volume of red blood cells as well as reduction in the mean haemoglobin concentration in the blood. Haemoglobin is responsible for carrying oxygen to tissues and organs in the body. Anaemia can be a particularly serious problem for pregnant women, leading to premature delivery and low birth weight. Iron deficiency anaemia is the most common micronutrient deficiency, and anaemia is often described as an indicator of both poor nutrition and poor health. Aim: The aim of this study was to determine the prevalence and risk factors associated with anaemia among antenatal care attendants at the Mamobi General Hospital Methods: This was a descriptive cross-sectional study that was conducted among pregnant women attending the Mamobi General Hospital. Structured questionnaire that was used in a similar study conducted by various authors was revised and adopted in this study. Results was analyzed using Stata version 15 and presented as mean, standard deviations, percentages, chi-square and logistic regression. The significance level was set at p<0.05. Results: A total of 372 pregnant women were enrolled in the study with a mean age (±SD) 28.47 (±5.74) years. The prevalence of anaemia was 53.3% (62.7% mild, 35.9% moderate and 1.4% severe). Maternal anaemia was significantly associated with participant’s religion (p=0.032) and folic acid consumption (p=0.038) after controlling for confounders. Conclusion: The overall prevalence of anaemia in pregnancy was 53.3%. Folic acid tablet supplementation and religion were associated with anaemia. It was therefore recommended that health workers, particularly health promoters and midwives should intensify health promotion to help reduce anaemia among the pregnant women.Item Extraction And Characterization Of Cellulose Nanocrystals From Two Local Plant Materials(University of Ghana, 2019-07) Zanu, F.Cellulose is a linear homopolysaccharide of repeating D-glucopyranose units which form about 15 – 20 % of the dry weight of plant biomass. It is the world’s most abundant renewable natural polymer with unique properties such as high strength, biocompatibility, low density and excellent mechanical properties. These excellent characteristics of the isolated cellulose nanocrystals coupled with their wide availability enable their potential application in areas of packaging materials to replace fossil-fuel based materials, in optical sensors, paints, and as reinforcements in composite materials. In this work, cellulose nanocrystals were isolated from two local plant biomass, Acasia sp. (sawie), and Palmae sp. (keteku), through a series of acid and alkaline hydrolysis to get rid of lignin, hemicellulose and other impurities, leaving crystalline cellulose nanocrystals. Cellulose nanocrystals were characterized by Fourier Transform Infra-Red (FT-IR) Spectroscopy, Optical Microscopy, Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and Thermogravimetric Analysis (TGA). SEM morphological analysis showed slender nanosize particles of CNCs of approximately less than 10 μm. FTIR analysis confirmed a removal of lignin and hemicellulose due to the disappearance of peaks at 1230 cm-1 (C – O bending) and 1765 – 1715 cm-1 (C = O stretching of aldehyde) respectively. Peak at 1160 cm-1 showed the presence of sulphonated groups which was evidenced by the uniform dispersibility of CNCs in solution due to the repulsive forces. The crystallinity index at 2Ꝋ (18o – 25o) was approximately -163.04 % for acacia sp. and -5460 % for palmae sp. Thermogravimetric analysis of both acacia sp. and palmae sp. showed high thermal stability of approximately 363.8 oC and 336.3 oC respectively. The characterized CNCs generally exhibited outstanding properties of high crystallinity, thermal stability and tunable surfaces enabling even dispersion in aqueous solution. Cellulose is a linear homopolysaccharide of repeating D-glucopyranose units which form about 15 – 20 % of the dry weight of plant biomass. It is the world’s most abundant renewable natural polymer with unique properties such as high strength, biocompatibility, low density and excellent mechanical properties. These excellent characteristics of the isolated cellulose nanocrystals coupled with their wide availability enable their potential application in areas of packaging materials to replace fossil-fuel based materials, in optical sensors, paints, and as reinforcements in composite materials. In this work, cellulose nanocrystals were isolated from two local plant biomass, Acasia sp. (sawie), and Palmae sp. (keteku), through a series of acid and alkaline hydrolysis to get rid of lignin, hemicellulose and other impurities, leaving crystalline cellulose nanocrystals. Cellulose nanocrystals were characterized by Fourier Transform Infra-Red (FT-IR) Spectroscopy, Optical Microscopy, Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and Thermogravimetric Analysis (TGA). SEM morphological analysis showed slender nanosize particles of CNCs of approximately less than 10 μm. FTIR analysis confirmed a removal of lignin and hemicellulose due to the disappearance of peaks at 1230 cm-1 (C – O bending) and 1765 – 1715 cm-1 (C = O stretching of aldehyde) respectively. Peak at 1160 cm-1 showed the presence of sulphonated groups which was evidenced by the uniform dispersibility of CNCs in solution due to the repulsive forces. The crystallinity index at 2Ꝋ (18o – 25o) was approximately -163.04 % for acacia sp. and -5460 % for palmae sp. Thermogravimetric analysis of both acacia sp. and palmae sp. showed high thermal stability of approximately 363.8 oC and 336.3 oC respectively. The characterized CNCs generally exhibited outstanding properties of high crystallinity, thermal stability and tunable surfaces enabling even dispersion in aqueous solution.Item Investigation of the Efficacy and Chemical Composition of Selected Traditional Medicines Used to Treat Onchocerciasis and Schistosomiasis in Ghana(University of Ghana, 2020-10) Bonsu, E.Y.In this study, two traditional medicines used to treat schistosomiasis (NTD-B4) and onchocerciasis (NTD-O4) in Ghana, were investigated to substantiate their claimed efficacy and to isolate the bioactive ingredients through bioassay-guided fractionation. Crude extracts of these remedies were prepared by successive extraction with DCM and methanol via cold percolation. Biological activities of the resulting crude extracts were evaluated in in vitro anti-schistosomal and anti-onchocercal assays against Schistosoma mansoni and Onchocerca ochengi, respectively. Further, the samples were screened for antitrypanosomal activity against Trypanosoma brucei brucei. NTD-B4-DCM exhibited 100% and 78.4 ± 2.8% inhibition effect against the schistosomula and adult worms of S. mansoni, respectively. The recorded IC50 value was 30.5 μg/mL. NTD-O4-DCM was not active against its target disease, onchocerciasis. It showed a percentage inhibition of 25%, 100 ± 0%, and 28.8 ± 0.0% against the microfilaria, adult male, and adult female worms of O. ochengi, respectively. Both extracts, however, showed promising activity against T. brucei brucei (IC50=5.63 ± 0.8 μg/mL for NTD-B4-DCM, and 8.69 ± 1.55 μg/mL for NTD-O4-DCM). Following the promising outcome of the antitrypanosomal assay, the crude extracts were selected for bioassay-guided fractionation. Fractionation of NTD-B4-DCM and subsequent isolation of bioactive compounds led to the identification of an eupatoriochromene-rich oil (42.6%) via GC-MS, which was 1.3-fold (IC50 <0.0977 μg/mL) more active than the standard antitrypanosomal drug, diminazene aceturate (IC50 = 0.13 μg/mL). Fractionation and isolation of bioactive compounds from NTD-O4-DCM also led to the identification of oil Dr/F-1/E-1/ML, with favorable activity (IC50= 1.51 ± 0.65 μg/mL), which precipitated a white flaky solid which was proposed to be hexyl 9-oxo-decanoate via the acquired 1D and 2D-NMR data.Item Indoor Air Quality Assessment. A Pilot Study at the University of Ghana(University of Ghana, 2020-10) Addo, R.Y.Polycyclic Aromatic Hydrocarbons (PAHs) are a class of unique carcinogenic and mutagenic pollutants and are the byproducts of incomplete combustion of organic materials such as fossil fuels, wood and tobacco. PAHs are distributed in the environment (i.e. air, soil and water). The health effects of PAHs are driven by exposure. Assessment of human exposure to PAHs in ambient air can be accomplished by monitoring the concentration of PAHs in the environment. The concentrations and compositional patterns of the 16 PAHs prioritized by US Environmental Protection Agency (EPA) were determined in organic film on glass window surfaces in different buildings on University of Ghana (UG) campus with the view of providing the information on the extent of contamination, sources of pollution and human health risk of PAHs in the organic film. The analyses were performed by means of GC-MS after soxhlex extraction with hexane and acetone (1:1). The concentration levels of the 16 USEPA PAHs in the organic film ranged from 126.8μg/kg to 628.8μg/kg with a mean value of 336 ± 190 μg/kg. A concentration gradient of the total PAHs was observed as follows; African Studies Department Library˃ Jones Quartey˃ Sarbah Dining Hall˃ Balme Library˃ Central Cafeteria˃ University of Ghana Basic School> Chemistry Lower Lecture Theater. The distribution was characterized by 2-4 rings PAHs contributing about 82% of the total PAHs in the studied area. Assessment of their sources using diagnostic ratio showed that emission of PAHs was mostly from fossil fuel combustion. The Σ8PAH (carcinogenic) concentration ranged from 38.9μg/kg to 75μg/kg. The estimated BaPeq (Cancer Risk Level) varied from 13.0μg/kg to 17.7μg/kg. The results show low BaPeq as compared to 600μg/kg which according to Canadian ministry of Ecology corresponds to a carcinogenic risk for persons (based on an incremental lifetime cancer risk (ILCR) of 10-6).Item Extraction and Characterization of Cellulose Nanocrystals from Two Local Plant Materials(University of Ghana, 2019-07) Zanu, F.Cellulose is a linear homopolysaccharide of repeating D-glucopyranose units which form about 15 – 20 % of the dry weight of plant biomass. It is the world’s most abundant renewable natural polymer with unique properties such as high strength, biocompatibility, low density and excellent mechanical properties. These excellent characteristics of the isolated cellulose nanocrystals coupled with their wide availability enable their potential application in areas of packaging materials to replace fossil-fuel based materials, in optical sensors, paints, and as reinforcements in composite materials. In this work, cellulose nanocrystals were isolated from two local plant biomass, Acasia sp. (sawie), and Palmae sp. (keteku), through a series of acid and alkaline hydrolysis to get rid of lignin, hemicellulose and other impurities, leaving crystalline cellulose nanocrystals. Cellulose nanocrystals were characterized by Fourier Transform Infra-Red (FT-IR) Spectroscopy, Optical Microscopy, Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and Thermogravimetric Analysis (TGA). SEM morphological analysis showed slender nanosize particles of CNCs of approximately less than 10 μm. FTIR analysis confirmed a removal of lignin and hemicellulose due to the disappearance of peaks at 1230 cm-1 (C – O bending) and 1765 – 1715 cm-1 (C = O stretching of aldehyde) respectively. Peak at 1160 cm-1 showed the presence of sulphonated groups which was evidenced by the uniform dispersibility of CNCs in solution due to the repulsive forces. The crystallinity index at 2Ꝋ (18o – 25o) was approximately -163.04 % for acacia sp. and -5460 % for palmae sp. Thermogravimetric analysis of both acacia sp. and palmae sp. showed high thermal stability of approximately 363.8 oC and 336.3 oC respectively. The characterized CNCs generally exhibited outstanding properties of high crystallinity, thermal stability and tunable surfaces enabling even dispersion in aqueous solution.Item Green Synthesis of Iron Nanoparticles (FeNPs) Using Plant Extracts and their Application in the Degradation of A Vat Dye(University of Ghana, 2019-07) Ohemeng., P. O.The growing concern for environmental sustainability calls for the adoption of ‘greener’ techniques for remediation purposes. The application of green synthesized iron nanoparticles (FeNPs) provides a promising route in this context. This thesis reports a facile room-temperature synthesis of stable iron nanoparticles utilizing aqueous extract of peels of Musa sp. (Plantain) and Tetrapleura sp. (‘Prekese’). The extracts served as both reductants and capping agents owing to the myriad of polyphenolic compounds present. Synthesized nanoparticles were confirmed through visual inspection of colour changes and by the use of spectroscopic and microscopic techniques. Microstructurally, the synthesized iron nanomaterials using Tetrapleura tetraptera were non-discrete particles whereas the plantain (Musa sp.) mediated synthesized iron nanoparticles were uniformly shaped with approximate diameter within 80 nm and 100 nm range. Based on ultraviolet-visible (UV-Vis) data, prepared iron nanomaterials showed a maximum plasmon resonance absorbance at 300 nm, typical of nanoscale iron. Fourier transform infrared spectroscopy (FTIR) analysis indicated the presence of various functional groups, particularly hydroxyl, present in the extracts, which may be responsible for capping of nanoparticles. The synthesized iron nanomaterials exhibited good efficiency in the degradation of Vat orange dye. The degradation process was highly dependent on contact time, pH, temperature, initial adsorbate concentration, and adsorbent dose. The sorption equilibrium of the dye on the nanoparticles was reached within 240 min of subjecting the aqueous solution of dye to the synthesized nanoparticles and was best explained by the Freundlich adsorption model. The results from this study illustrate that biosynthesized iron nanomaterials offer a cost-effective, environmentally friendly and efficient means of remediation of dye-contaminated industrial effluents.Item Synthesis, Characterization and Luminescent Properties of Bipodal and Tripodal Pyrazole and Triazole Lanthanide Coordination Complexes(University of Ghana, 2019-07) Tofah , K.P.Lanthanide complexes have been established as promising agents in their application as catalysts and photo-luminescent materials. Recent research has been geared towards the optical application of these lanthanide complexes, especially as organic light-emitting diodes (OLED) for TV screens, phones and other portable electronic devices. The luminescent ability of these complexes is largely dependent on the choice of ligand environment. We report here for the first time lanthanide complexes bearing three classes of ligands, mainly a heteroscorpionate (N^N^O) ligand of the form Pz2R(CHPhOH) (Figure 1.0-A), (N^N) 1-(2-Picolyl)-4-phenyl-1H- 1,2,3-triazole (Figure 1.0-B) and (N^N) 3,6-(dipyridyl)-1,2,4,5-tetrazine (Figure 1.0-C). The coordination complex of the lanthanum salts (Pr, Dy, Gd and Tb), have been synthesized and characterized by 1H-NMR, 13C-NMR and FT-IR. The electronic and luminescence property of the ligands and complexes have been studied using Cyclic Voltammetry, UV-vis and spectro-fluorophotometric studies.