Investigating long-term host-parasite dynamics in odontocetes in Southern Africa
- Authors: Adams, Inge Alison
- Date: 2018
- Subjects: Biological invasions -- Environmental aspects , Cetacea -- Indian Ocean , Ecological disturbances
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23437 , vital:30543
- Description: Cetaceans are a very diverse family and globally, various aspects about their biology have been studied, including infection by parasites. Twenty-five dolphin species can be found in the South African subregion and very little information is available detailing which parasites are infecting them. Parasite samples have been collected opportunistically since the 1970’s from dolphins incidentally caught in shark nets off the KwaZulu-Natal coastline as well as from dolphins stranded along the Eastern Cape coastline. These samples have been stored in the Graham Ross Marine Mammal Collection at the Port Elizabeth Museum and samples belonging to eight odontocete species have been used in the present analysis. These eight species are: the Indian Ocean Humpback Dolphin (Sousa plumbea), the Indo-Pacific Bottlenose Dolphin (Tursiops aduncus), the Long-beaked Common Dolphin (Delphinus capensis), the Risso’s Dolphin (Grampus griseus), the Pantropical Spotted Dolphin (Stenella attenuata), the Striped Dolphin (Stenella coeruleoalba), the Pygmy Sperm Whale (Kogia breviceps) and the Dwarf Sperm Whale (Kogia breviceps). This study aims to investigate which parasites are infecting odontocetes in Southern Africa. Secondly, this study aims to investigate whether any trends in infection exist between sexes, age groups, cause of death and over time. Eighteen parasite species were found to infect odontocetes in Southern Africa. Two could only be identified to family level, seven to genus level and eight to species level. Only one parasite, a trematode, could not be identified and several parasite species were new host records for the subregion. Results showed that the prevalence of parasitic infection has increased over the last four decades, prompting questions regarding the health of our oceans. This study is the first to comprehensively investigate which parasite species are found in these eight odontocete species in Southern Africa. This baseline data will contribute greatly to other types of research involving parasites and provides us with information regarding the health of our ocean.
- Full Text:
- Date Issued: 2018
- Authors: Adams, Inge Alison
- Date: 2018
- Subjects: Biological invasions -- Environmental aspects , Cetacea -- Indian Ocean , Ecological disturbances
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23437 , vital:30543
- Description: Cetaceans are a very diverse family and globally, various aspects about their biology have been studied, including infection by parasites. Twenty-five dolphin species can be found in the South African subregion and very little information is available detailing which parasites are infecting them. Parasite samples have been collected opportunistically since the 1970’s from dolphins incidentally caught in shark nets off the KwaZulu-Natal coastline as well as from dolphins stranded along the Eastern Cape coastline. These samples have been stored in the Graham Ross Marine Mammal Collection at the Port Elizabeth Museum and samples belonging to eight odontocete species have been used in the present analysis. These eight species are: the Indian Ocean Humpback Dolphin (Sousa plumbea), the Indo-Pacific Bottlenose Dolphin (Tursiops aduncus), the Long-beaked Common Dolphin (Delphinus capensis), the Risso’s Dolphin (Grampus griseus), the Pantropical Spotted Dolphin (Stenella attenuata), the Striped Dolphin (Stenella coeruleoalba), the Pygmy Sperm Whale (Kogia breviceps) and the Dwarf Sperm Whale (Kogia breviceps). This study aims to investigate which parasites are infecting odontocetes in Southern Africa. Secondly, this study aims to investigate whether any trends in infection exist between sexes, age groups, cause of death and over time. Eighteen parasite species were found to infect odontocetes in Southern Africa. Two could only be identified to family level, seven to genus level and eight to species level. Only one parasite, a trematode, could not be identified and several parasite species were new host records for the subregion. Results showed that the prevalence of parasitic infection has increased over the last four decades, prompting questions regarding the health of our oceans. This study is the first to comprehensively investigate which parasite species are found in these eight odontocete species in Southern Africa. This baseline data will contribute greatly to other types of research involving parasites and provides us with information regarding the health of our ocean.
- Full Text:
- Date Issued: 2018
Photocatalytic reduction of CO2 by cobalt doped TiO2 and ZnO micro/nanostructured materials
- Authors: Mgolombane, Mvano
- Date: 2020
- Subjects: Nanostructures , Catalysis , Nanotechnology , Chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49171 , vital:41607
- Description: Large emissions of carbon dioxide (CO2) in the atmosphere have caused many harmful effects on humans and the environment. Carbon dioxide is a good source C and is used in a number of applications such as synthesis of fossil fuels. Redox reaction of CO2 and H2O with photocatalysts such as TiO2 and ZnO to produce solar fuels is a promising approach in reducing the environmental impacts of greenhouse gasses. This dissertation describes an in-depth synthesis of four photochemical catalysts and their photocatalytic conversion of CO2 to methanol, thereby addressing the above-mentioned problems by applying synthesised nano-based catalysts. Prior to photocatalytic reduction studies, catalysts such as TiO2, Co-doped TiO2, Co-doped TiO2/rGO, ZnO, Co-doped ZnO and Co-doped ZnO/rGO were synthesized and characterized using various spectroscopic and imaging techniques such as Powder X-Ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), Transmission Electron Micrograph (TEM), X-ray Photoelectron Spectroscopy (XPS), Brunner- Emmet- Teller measurement (BET), Thermogravimetry Analysis (TGA) and UV-Vis Diffuse Reflectance Spectroscopy (UV-Vis-DRS). The conversion yield of CO2 to methanol on TiO2, Co-doped TiO2 and Co-doped TiO2/rGO reached 32.3 μmol/gcat, 730 μmol/gcat and 936 μmol/gcat, respectively, after 7 h of irradiation. Theoretical studies via Density functional theory (DFT) revealed that doping TiO2 with Co ions facilitated the formation of adsorbed carbonate or CO2•- species, as CO2 adsorbs onto Co-doped TiO2 surface with binding energy (BE) of -18.12 KJ/mol. The photocatalytic activities of ZnO-based nanomaterials found that Co-doped ZnO/rGO with high ratio of Co, reduced graphene (rGO) and large surface area (10.62 m2g-1) possessed higher CH3OH (30.1 μmol/g) in comparison with Co-doped ZnO (27.3 μmol/g) and ZnO (7.5 μmol/g). The research will deepen the understanding that TiO2 based photocatalyst show higher activity and the mole ratio (Ti/Zn:Co) influences nanocomposites performance and provide new ideas for designing efficient photocatalysts.
- Full Text:
- Date Issued: 2020
- Authors: Mgolombane, Mvano
- Date: 2020
- Subjects: Nanostructures , Catalysis , Nanotechnology , Chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49171 , vital:41607
- Description: Large emissions of carbon dioxide (CO2) in the atmosphere have caused many harmful effects on humans and the environment. Carbon dioxide is a good source C and is used in a number of applications such as synthesis of fossil fuels. Redox reaction of CO2 and H2O with photocatalysts such as TiO2 and ZnO to produce solar fuels is a promising approach in reducing the environmental impacts of greenhouse gasses. This dissertation describes an in-depth synthesis of four photochemical catalysts and their photocatalytic conversion of CO2 to methanol, thereby addressing the above-mentioned problems by applying synthesised nano-based catalysts. Prior to photocatalytic reduction studies, catalysts such as TiO2, Co-doped TiO2, Co-doped TiO2/rGO, ZnO, Co-doped ZnO and Co-doped ZnO/rGO were synthesized and characterized using various spectroscopic and imaging techniques such as Powder X-Ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), Transmission Electron Micrograph (TEM), X-ray Photoelectron Spectroscopy (XPS), Brunner- Emmet- Teller measurement (BET), Thermogravimetry Analysis (TGA) and UV-Vis Diffuse Reflectance Spectroscopy (UV-Vis-DRS). The conversion yield of CO2 to methanol on TiO2, Co-doped TiO2 and Co-doped TiO2/rGO reached 32.3 μmol/gcat, 730 μmol/gcat and 936 μmol/gcat, respectively, after 7 h of irradiation. Theoretical studies via Density functional theory (DFT) revealed that doping TiO2 with Co ions facilitated the formation of adsorbed carbonate or CO2•- species, as CO2 adsorbs onto Co-doped TiO2 surface with binding energy (BE) of -18.12 KJ/mol. The photocatalytic activities of ZnO-based nanomaterials found that Co-doped ZnO/rGO with high ratio of Co, reduced graphene (rGO) and large surface area (10.62 m2g-1) possessed higher CH3OH (30.1 μmol/g) in comparison with Co-doped ZnO (27.3 μmol/g) and ZnO (7.5 μmol/g). The research will deepen the understanding that TiO2 based photocatalyst show higher activity and the mole ratio (Ti/Zn:Co) influences nanocomposites performance and provide new ideas for designing efficient photocatalysts.
- Full Text:
- Date Issued: 2020
New synergic biomaterials for anti-cancer therapy
- Authors: Swanepoel, Bresler
- Date: 2019
- Subjects: Pharmaceutical chemistry , Cancer -- Research , Biomedical materials
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43957 , vital:37087
- Description: In the last two decades, anti-cancer therapy has grown considerably with the help of both natural and synthetic anti-cancer compounds but, the search for new and improved cancer treatment remains an ongoing and important issue. Some anti-cancer compounds such as cisplatin are limited by their toxicity in normal tissues and the development of drug resistance. Therefore, in order to address drug resistance and side-effects of anti-cancer agents, recent research has been focusing on finding novel combinations of anti-cancer agents that have non-overlapping mechanisms of action. The first objective of this study was to determine the mechanism of action of Anemone nemorosa, Artemisia afra, N-[[3-(4-bromophenyl)-1H-pyrazol-5-yl]-carbamothioyl]-4-chloro-benzamide (BC-7) and N-benzoyl-N’-(3-(4-bromophenyl)-1H-pyrazol-5-yl)-thiourea (BT-7) through cell cycle arrest, phosphatidylserine translocation (PS), caspase activation and mitochondrial membrane depolarization. This study has shown that A. nemorosa, BC-7 and A. afra are capable of inducing cell death within three cancer cell lines namely HeLa, MeWo and HepG2, at varying degrees. HeLa cells were the most susceptible to treatment with A. nemorosa and BC-7 with IC50 values of 20.33 ± 2.480 μg/ml and 65.58 ± 8.400 μM (28.58 ± 3.660 μg/ml), respectively. A. afra was the most active against HepG2 cells with an IC50 value of 37.55 μg/ml. BT-7 was not cytotoxic against any of the cancer cell lines. The effects on HeLa cells and their progression through the cell cycle indicated that cells were arrested in the early M phase for all treatments. The induction of apoptosis was confirmed by an increase in PS translocation and activation of caspase 3 and 8 as well as a decrease in the mitochondrial membrane potential. It was deduced that A. nemorosa, A. afra and BC-7 induce caspase-dependent apoptosis in a mitochondrial dependent manner. The second objective of this study was to investigate the potential of A. nemorosa, A. afra and BC-7 to target various mediators involved in the inflammatory response as an alternative method in which cell death may be induced. Most treatments indicated that a tumour-elicited inflammatory response is indeed induced in HeLa cells and that the significant activation of nuclear factor kappa B (NF-κB) favoured the production of nitric oxide (NO) over cyclo-oxygenase 2 (COX-2). However, treatments with A. nemorosa, BC-7 and A. afra at their IC10 showed the potential of inhibiting this response. ROS levels were increased by most treatments and support the idea of ROS-mediated apoptosis. The third objective was to investigate combination treatments of these extracts and compounds for their potential synergistic cytotoxic activity and thus formulating the combinations as potential anti-cancer agents. Thirty combination mixtures were prepared using the IC50 values of each extract or compound at ratios of 1:3, 1:2, 1:1, 2:1 and 3:1, respectively. The cytotoxic/anti-proliferative activity of each mixture was determined by the bisBenzamide H 33342 trihydrochloride/propidium iodide (Hoechst 33342/PI) dual staining method on HeLa cervical cancer cells. The combination index (CI) values, at inhibition of 50% of HeLa cell growth, for each combination mixture, were determined by means of the Chou and Talalay method. The combined effect can then be indicated as CI < 1, synergism; CI = 1, additive effect or CI > 1, antagonism, respectively. Most combination treatments showed to have an antagonistic effect except for cisplatin:BC-7 (1:3, 1:1, 2:1, 3:1) and cisplatin:A. afra (1:3, 1:2, 1:1, 3:1) combinations that showed synergism. The 1:2 ratio of cisplatin:BC-7 and the 2:1 ratio of cisplatin:A. afra were additive. CI values were also calculated at inhibition of 10, 25 and 75% of HeLa cell growth, for each combination mixture. Antagonistic effects were frequently observed at lower effect levels such as at 10 and 25% inhibition of growth. However, this was not seen for the cisplatin:BC-7 combinations as all the ratios indicated synergism. Some of these ratios, such as the 1:3 and 1:2, even led to a greater degree of synergism being obtained, with noticeable antagonistic effects seen at 50 and 75% inhibition of growth. The current finding is that BC-7 and A. afra could lower the dose of cisplatin in combination to achieve a similar anti-cancer efficacy compared to the higher cisplatin dose when used alone. The lower dosage in combination could result in reduced drug resistance as well as limit the toxicity on normal cells associated with cisplatin treatment. In conclusion, this study shows, for the first time, that A. nemorosa has the potential to induce apoptosis and also has some anti- and pro-inflammatory activity in HeLa cancer cells. This study also enhanced the knowledge of the mechanism of apoptosis induction of BC-7, in a more detailed manner, as well as investigated its inflammatory effects for the first time. Results obtained for A. afra correlated nicely to previously reported studies and confirmed that the methods used in this study, although different, leads to the same conclusions. Combination treatments also indicated, for the first time, that BC-7 and A. afra have the ability to function in a synergic manner with cisplatin and proves that, although extensive research may have been done on a plant or compound, more can be discovered. This new information can lead to identification of new compounds in the plants and the integration of signalling pathways that can be targeted for treatment of cancer.
- Full Text:
- Date Issued: 2019
- Authors: Swanepoel, Bresler
- Date: 2019
- Subjects: Pharmaceutical chemistry , Cancer -- Research , Biomedical materials
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43957 , vital:37087
- Description: In the last two decades, anti-cancer therapy has grown considerably with the help of both natural and synthetic anti-cancer compounds but, the search for new and improved cancer treatment remains an ongoing and important issue. Some anti-cancer compounds such as cisplatin are limited by their toxicity in normal tissues and the development of drug resistance. Therefore, in order to address drug resistance and side-effects of anti-cancer agents, recent research has been focusing on finding novel combinations of anti-cancer agents that have non-overlapping mechanisms of action. The first objective of this study was to determine the mechanism of action of Anemone nemorosa, Artemisia afra, N-[[3-(4-bromophenyl)-1H-pyrazol-5-yl]-carbamothioyl]-4-chloro-benzamide (BC-7) and N-benzoyl-N’-(3-(4-bromophenyl)-1H-pyrazol-5-yl)-thiourea (BT-7) through cell cycle arrest, phosphatidylserine translocation (PS), caspase activation and mitochondrial membrane depolarization. This study has shown that A. nemorosa, BC-7 and A. afra are capable of inducing cell death within three cancer cell lines namely HeLa, MeWo and HepG2, at varying degrees. HeLa cells were the most susceptible to treatment with A. nemorosa and BC-7 with IC50 values of 20.33 ± 2.480 μg/ml and 65.58 ± 8.400 μM (28.58 ± 3.660 μg/ml), respectively. A. afra was the most active against HepG2 cells with an IC50 value of 37.55 μg/ml. BT-7 was not cytotoxic against any of the cancer cell lines. The effects on HeLa cells and their progression through the cell cycle indicated that cells were arrested in the early M phase for all treatments. The induction of apoptosis was confirmed by an increase in PS translocation and activation of caspase 3 and 8 as well as a decrease in the mitochondrial membrane potential. It was deduced that A. nemorosa, A. afra and BC-7 induce caspase-dependent apoptosis in a mitochondrial dependent manner. The second objective of this study was to investigate the potential of A. nemorosa, A. afra and BC-7 to target various mediators involved in the inflammatory response as an alternative method in which cell death may be induced. Most treatments indicated that a tumour-elicited inflammatory response is indeed induced in HeLa cells and that the significant activation of nuclear factor kappa B (NF-κB) favoured the production of nitric oxide (NO) over cyclo-oxygenase 2 (COX-2). However, treatments with A. nemorosa, BC-7 and A. afra at their IC10 showed the potential of inhibiting this response. ROS levels were increased by most treatments and support the idea of ROS-mediated apoptosis. The third objective was to investigate combination treatments of these extracts and compounds for their potential synergistic cytotoxic activity and thus formulating the combinations as potential anti-cancer agents. Thirty combination mixtures were prepared using the IC50 values of each extract or compound at ratios of 1:3, 1:2, 1:1, 2:1 and 3:1, respectively. The cytotoxic/anti-proliferative activity of each mixture was determined by the bisBenzamide H 33342 trihydrochloride/propidium iodide (Hoechst 33342/PI) dual staining method on HeLa cervical cancer cells. The combination index (CI) values, at inhibition of 50% of HeLa cell growth, for each combination mixture, were determined by means of the Chou and Talalay method. The combined effect can then be indicated as CI < 1, synergism; CI = 1, additive effect or CI > 1, antagonism, respectively. Most combination treatments showed to have an antagonistic effect except for cisplatin:BC-7 (1:3, 1:1, 2:1, 3:1) and cisplatin:A. afra (1:3, 1:2, 1:1, 3:1) combinations that showed synergism. The 1:2 ratio of cisplatin:BC-7 and the 2:1 ratio of cisplatin:A. afra were additive. CI values were also calculated at inhibition of 10, 25 and 75% of HeLa cell growth, for each combination mixture. Antagonistic effects were frequently observed at lower effect levels such as at 10 and 25% inhibition of growth. However, this was not seen for the cisplatin:BC-7 combinations as all the ratios indicated synergism. Some of these ratios, such as the 1:3 and 1:2, even led to a greater degree of synergism being obtained, with noticeable antagonistic effects seen at 50 and 75% inhibition of growth. The current finding is that BC-7 and A. afra could lower the dose of cisplatin in combination to achieve a similar anti-cancer efficacy compared to the higher cisplatin dose when used alone. The lower dosage in combination could result in reduced drug resistance as well as limit the toxicity on normal cells associated with cisplatin treatment. In conclusion, this study shows, for the first time, that A. nemorosa has the potential to induce apoptosis and also has some anti- and pro-inflammatory activity in HeLa cancer cells. This study also enhanced the knowledge of the mechanism of apoptosis induction of BC-7, in a more detailed manner, as well as investigated its inflammatory effects for the first time. Results obtained for A. afra correlated nicely to previously reported studies and confirmed that the methods used in this study, although different, leads to the same conclusions. Combination treatments also indicated, for the first time, that BC-7 and A. afra have the ability to function in a synergic manner with cisplatin and proves that, although extensive research may have been done on a plant or compound, more can be discovered. This new information can lead to identification of new compounds in the plants and the integration of signalling pathways that can be targeted for treatment of cancer.
- Full Text:
- Date Issued: 2019
An investigation of the long term chemical stability and physical performance of PMD-citronellal acetal compared with dibutyl phthalate and BIS(2-ethylhexyl) terephthalate as plasticisers in selected cosmetic formulations
- Authors: Marx, Amor
- Date: 2019
- Subjects: Plastics -- Additives , Chemistry, Technical , Cosmetics
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: http://hdl.handle.net/10948/42574 , vital:36669
- Description: Plasticisers are used by cosmetic manufacturers to improve the film forming abilities of a product and increase flexibility of the film formed on the skin or hair surface, as is desired, for example, in nail lacquers and lip coats. In recent years authorities have banned several plasticisers in cosmetic products (mainly phthalates) since these substances may pose a wide range of health risks and can be harmful to the environment. It is, therefore, necessary to find alternative, safe plasticisers, preferably of natural origin e.g. bio-plasticisers which can replace the toxic phthalates and still impart the same desirable properties to the cosmetic products in which they are used. In this study, the novel bio-plasticiser para-menthane-3,8-diol-citronellal acetal (PMD-citronellal acetal) was selected to compare its stability properties and plasticising behaviour with well-known non-phthalate bis(2-ethylhexyl) terephthalate (DEHT) and the problematic dibutyl phthalate (DBP). The objectives were to determine if the novel bio-plasticiser PMD-citronellal acetal plasticising properties and chemical stability are similar or better than DEHT and DBP within two cosmetic formulations, viz. a nail lacquer and a lip coat formulation, after being incubated at elevated temperature (40 ˚C) over a three month period. The results showed that flexibility for all plasticised formulations remained stable at room temperature (21 ˚C) and elevated temperature (40 ˚C). Adhesion performance of DEHT and PMD-citronellal acetal nail lacquer formulations outperformed DBP nail lacquer formulations. Elevated temperature and storage time had no influence on the organoleptic properties of any plasticised formulation. PMD-citronellal acetal plasticised lip coat and nail lacquer formulations outperformed both DEHT and DBP nail formulations with regard to hardness. Fourier Transform Infrared Spectrometry (FTIR) studies revealed that neat DPB, DEHT and Acetal were chemically stable at room temperature and elevated temperature over a three month incubation period. Furthermore, the three plasticised nail lacquer and lip coat formulations remained chemical stable over the three month incubation period at elevated temperature. Chemical stability of the nail lacquer formulations was further evaluated by means of leaching tests using Solid Phase Extraction [1] and Ultra-Performance Liquid Chromatography (UPLC) at two temperatures (31 and 50 °C) and three time intervals (24, 48 and 72 hours). No leaching out of the nail lacquer formulation for Acetal and DEHT could be detected. It was observed that trace amounts of DBP leached from the nail lacquer formulation at 50 °C. DBP leaching decreased over time and was found to be statistically significant over the studied period. It can be concluded that PMD-citronellal acetal can be selected as bio-plasticiser which exhibits similar properties to DEHT based on the performance stability and non-leaching criteria, and can be used as an alternative plasticiser to the toxic DBP in cosmetic formulations.
- Full Text:
- Date Issued: 2019
- Authors: Marx, Amor
- Date: 2019
- Subjects: Plastics -- Additives , Chemistry, Technical , Cosmetics
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: http://hdl.handle.net/10948/42574 , vital:36669
- Description: Plasticisers are used by cosmetic manufacturers to improve the film forming abilities of a product and increase flexibility of the film formed on the skin or hair surface, as is desired, for example, in nail lacquers and lip coats. In recent years authorities have banned several plasticisers in cosmetic products (mainly phthalates) since these substances may pose a wide range of health risks and can be harmful to the environment. It is, therefore, necessary to find alternative, safe plasticisers, preferably of natural origin e.g. bio-plasticisers which can replace the toxic phthalates and still impart the same desirable properties to the cosmetic products in which they are used. In this study, the novel bio-plasticiser para-menthane-3,8-diol-citronellal acetal (PMD-citronellal acetal) was selected to compare its stability properties and plasticising behaviour with well-known non-phthalate bis(2-ethylhexyl) terephthalate (DEHT) and the problematic dibutyl phthalate (DBP). The objectives were to determine if the novel bio-plasticiser PMD-citronellal acetal plasticising properties and chemical stability are similar or better than DEHT and DBP within two cosmetic formulations, viz. a nail lacquer and a lip coat formulation, after being incubated at elevated temperature (40 ˚C) over a three month period. The results showed that flexibility for all plasticised formulations remained stable at room temperature (21 ˚C) and elevated temperature (40 ˚C). Adhesion performance of DEHT and PMD-citronellal acetal nail lacquer formulations outperformed DBP nail lacquer formulations. Elevated temperature and storage time had no influence on the organoleptic properties of any plasticised formulation. PMD-citronellal acetal plasticised lip coat and nail lacquer formulations outperformed both DEHT and DBP nail formulations with regard to hardness. Fourier Transform Infrared Spectrometry (FTIR) studies revealed that neat DPB, DEHT and Acetal were chemically stable at room temperature and elevated temperature over a three month incubation period. Furthermore, the three plasticised nail lacquer and lip coat formulations remained chemical stable over the three month incubation period at elevated temperature. Chemical stability of the nail lacquer formulations was further evaluated by means of leaching tests using Solid Phase Extraction [1] and Ultra-Performance Liquid Chromatography (UPLC) at two temperatures (31 and 50 °C) and three time intervals (24, 48 and 72 hours). No leaching out of the nail lacquer formulation for Acetal and DEHT could be detected. It was observed that trace amounts of DBP leached from the nail lacquer formulation at 50 °C. DBP leaching decreased over time and was found to be statistically significant over the studied period. It can be concluded that PMD-citronellal acetal can be selected as bio-plasticiser which exhibits similar properties to DEHT based on the performance stability and non-leaching criteria, and can be used as an alternative plasticiser to the toxic DBP in cosmetic formulations.
- Full Text:
- Date Issued: 2019
An intergrated continuous flow system for the manufacture of biodiesel from waste cooking oil using a heterogeneous acid catalyst and homogeneous base catalyst
- Authors: Mathe,Francis Matota
- Date: 2017
- Subjects: Biodiesel fuels industry , Catalysis , Vegetable oils as fuel
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/44460 , vital:37837
- Description: The continuous flow production of biodiesel from waste cooking oil (WCO) was investigated in this study. Two different methods of biodiesel production were investigated. The first method involved the acid esterification of free fatty acids (FFAs). In the biodiesel community, the esterification of FFAs in WCO is usually regarded as the pre-treatment stage of biodiesel production using low-quality feedstock.The second method involved the transesterification of triglycerides in WCO. Homogeneous catalysts (NaOH or H2SO4) and heterogeneous catalysts (NaOH/ZnO, Sn/ZnO, Amberlyst-15, Amberlite-IRA 904, Fe/Bentonite and Amberlite IRN 78) were evaluated in the transesterification reaction. Catalyst screening was done using a batch reactor. NaOH gave a high úME content of 96.7% and was chosen as the optimum catalyst for the reaction.The main aim of the project was to make an integrated system that incorporates the esterification and transesterification reaction in the flow production of biodiesel using WCO. The system was developed using the conditions obtained from optimum studies of the separate reactions. Slight adjustments based on further experimental work were made to create an efficient system. The effect of excess methanol from the first step on the concentration of NaOH in the second phase was investigated. It was shown that the excess methanol decreases the concentration of the NaOH and this decreases the úMEs in the final mixture of biodiesel.
- Full Text:
- Date Issued: 2017
- Authors: Mathe,Francis Matota
- Date: 2017
- Subjects: Biodiesel fuels industry , Catalysis , Vegetable oils as fuel
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/44460 , vital:37837
- Description: The continuous flow production of biodiesel from waste cooking oil (WCO) was investigated in this study. Two different methods of biodiesel production were investigated. The first method involved the acid esterification of free fatty acids (FFAs). In the biodiesel community, the esterification of FFAs in WCO is usually regarded as the pre-treatment stage of biodiesel production using low-quality feedstock.The second method involved the transesterification of triglycerides in WCO. Homogeneous catalysts (NaOH or H2SO4) and heterogeneous catalysts (NaOH/ZnO, Sn/ZnO, Amberlyst-15, Amberlite-IRA 904, Fe/Bentonite and Amberlite IRN 78) were evaluated in the transesterification reaction. Catalyst screening was done using a batch reactor. NaOH gave a high úME content of 96.7% and was chosen as the optimum catalyst for the reaction.The main aim of the project was to make an integrated system that incorporates the esterification and transesterification reaction in the flow production of biodiesel using WCO. The system was developed using the conditions obtained from optimum studies of the separate reactions. Slight adjustments based on further experimental work were made to create an efficient system. The effect of excess methanol from the first step on the concentration of NaOH in the second phase was investigated. It was shown that the excess methanol decreases the concentration of the NaOH and this decreases the úMEs in the final mixture of biodiesel.
- Full Text:
- Date Issued: 2017