By addressing new sample preparation techniques, the U.S. Environmental Protection Agency (EPA) has recently implemented research programs to reduce or abolish laboratory pollution. In the work reported here, EPA Method 8270, established for Priority Pollutant Organics, will be evaluated by both Soxhlet and microwave-assisted extraction (MAE) for two classifications of compounds. The common procedure for sample preparation of solids is Soxhlet extraction. This is a lengthy operation and uses abundant solvent volumes. With ever changing times, the new technology of MAE is surfacing. This technique uses far less solvent and sample preparation times are greatly reduced. The work reported here compares the recoveries of phenolic and polynuclear aromatic compounds for both Soxhlet and closed-vessel MAE. / Master of Science

A soja e seus produtos são ricos em isoflavonóides, estes possuem a concentração aumentada após a fermentação microbiana, devido à liberação de fenólicos, através da conversão das formas glicosídicas em agliconas. O processo fermentativo em estado sólido por fungos filamentosos tem sido amplamente empregado como uma estratégica biotecnológica na busca de agregar valores aos produtos e subprodutos agroindustriais, principalmente elevando os teores de compostos bioativos. No presente estudo, foram avaliados o aumento dessas propriedades, como antioxidante e anti-inflamatória em diferentes substratos utilizando linhagens fúngicas do gênero Rhizopus sp. As 17 linhagens testadas foram capazes de elevar o potencial antioxidante dos grãos de soja. A fermentação de soja e arroz utilizando o R. oligosporus NRRL 2710 resultou em um incremento de 26,5 vezes o potencial antioxidante e 9,33 vezes o teor de compostos fenólicos nos extratos etanólicos, em 72 horas de processo. Além disso, mostraram resposta positiva para a atividade antiinflamatória, apresentando capacidade de inibição máxima de 70,75% e concentração inibitória de 4,2 mg mL. Os produtos fermentados pelo R. oligosporus NRRL 2710 foram submetidos a diferentes processos de extração: Soxhlet com diferentes solventes e supercrítica de CO2 + etanol (scCO2 + EtOH), o que permitiu verificar a relação entre a polaridade e o rendimento de extração. As extrações de Soxhlet foram realizadas usando amostras fermentadas secas e úmidas, os maiores valores de rendimento obtidos foram 42,09% e 32,84%, respectivamente. Este tipo de extração permitiu obter valores de atividade antioxidante na concentração inibitória (IC50) de 0,55 e 0,67 g g-1 e compostos fenólicos de 1,30 e 1,05 mg EAG g-1. Diferentes condições foram testadas no processo de extração com fluido comprimido (scCO2 + EtOH), para estudar a influência da pressão e temperatura no rendimento da extração. Os resultados mostraram que ambas as variáveis influenciam o rendimento do processo. Os extratos deste processo apresentaram um valor de IC50 de 0,17 g g-1, inibindo 94,05% do radical DPPH. Quanto aos compostos fenólicos, estes extratos apresentaram 1,39 mg EAG g-1. / The soybean and its products are rich in isoflavonoids, these have the increased concentration after the microbial fermentation, due to the release of phenolics, through the conversion of the glycosidic forms into aglycones. The solid state fermentative process by filamentous fungi has been widely used as a biotechnological strategy in the search of aggregating values to agroindustrial products and byproducts, mainly raising the levels of bioactive compounds. In the present study, the increase of these antioxidant and anti-inflammatory properties in different substrates using fungal strains of the genus Rhizopus sp. The 17 lines tested were able to raise the antioxidant potential of the soybean grains. The fermentation of soybean and rice using R. oligosporus NRRL 2710 resulted in an increase of 26.5 times the antioxidant potential and 9.33 times the content of phenolic compounds in the ethanolic extracts, in 72 hours of process. In addition, they showed a positive response to anti-inflammatory activity, with a maximum inhibitory capacity of 70.75% and an inhibitory concentration of 4.2 mg mL. The products fermented by R. oligosporus NRRL 2710 were submitted to different extraction processes: Soxhlet with different solvents and supercritical CO2 + ethanol (scCO2 + EtOH), which allowed to verify the relationship between polarity and extraction yield. Soxhlet extractions were performed using dry and wet fermented samples, the highest values of yield obtained were 42.09% and 32.84%, respectively. This type of extraction allowed to obtain values of antioxidant activity at the inhibitory concentration (IC50) of 0.55 and 0.67 g g-1 and phenolic compounds of 1.30 and 1.05 mg GAE g-1. Different conditions were tested in the compressed fluid extraction process (scCO2 + EtOH) to study the influence of pressure and temperature on extraction yield. The results showed that both variables influence the yield of the process. The extracts from this procedure had an IC50 value of 0.17 g g-1, inhibiting 94.05% of the DPPH radical. As for phenolic compounds, these extracts presented 1.39 mg GAE g-1.

Ce travail de thèse a pour but de suivre le comportement du liant ionomère après vieillissement en condition réelle d'utilisation de la pile. Dans un premier temps, diverses techniques de caractérisation en phase solide ont été utilisées afin d'étudier le ionomère présent dans les électrodes. La majeure partie de ces techniques se sont avérées insatisfaisantes pour le suivi du vieillissement du ionomère. Seule l'analyse par diffraction rayon X (DRX) a mis en avant un changement d'organisation structurale du ionomère dans les électrodes. Par la suite, nous avons choisi de caractériser le ionomère en solution après extraction par l'eau. Préalablement, un protocole de quantification en 2 à 3 étapes, dans lequel intervient une quantification via le rapport signal-sur-bruit (S/N), a été mis en place afin de quantifier le Nafion® et autres petites molécules fluorés. L'extraction Soxhlet a ensuite été réalisée sur les électrodes permettant de révéler la présence d'un produit de dégradation hydrosoluble après fonctionnement en pile, à la fois en cathode et en anode. Enfin, la macération des électrodes dans le diméthylacétamide (DMAc) a permis d'extraire le polymère Nafion® ainsi que deux acides : l'acide trifluoroacétique (TFA) et l'acide triflique (TFI). En conclusion, la corrélation de l'ensemble des observations nous a permis de proposer un mécanisme de dégradation du liant ionomère présent dans les électrodes. / The purpose of this study was to follow the behavior of ionomer binder after fuel cell operation. First, a series of techniques were used to investigate to characterize ionomer in electrode at solid state. Most of them were inefficient to study ionomer degradation. Only X-Ray Diffraction (XRD) pointed out a structural change of the binder in electrodes. Second, it has been decided to characterize ionomer in liquid state after water extraction. But first of all, a quantitative 19F NMR protocol composed of two to three steps, with a first step using a quantification through signal-to-noise ratio (S/N), was establish in order to quantify Nafion® and degradation products. Soxhlet extraction performed on electrodes allowed to detect a degradation product water-soluble. Finally, extraction with organic solvent (Dimethylacetamide) allowed to extract Nafion® and two acid: trifluoroacetic acid (TFA) and triflic acid (TFI) from electrodes. In conclusion, correlation between observation and literature allowed us to propose a degradation mechanism of ionomer in electrodes.

Made available in DSpace on 2017-07-10T17:59:30Z (GMT). No. of bitstreams: 1 Ana Claudia Cabral dos Santos.pdf: 1804875 bytes, checksum: 59accd259357d955c055e44645dee662 (MD5) Previous issue date: 2014-12-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Biodiesel is a fuel that can be obtained from renewable sources and due to its chemical composition is sensitive to oxidation. To increase their oxidative stability is necessary to add antioxidants, which are compounds capable of avoiding or delaying oxidation reactions and can be synthetic or natural, from the natural, we highlight a variety of plants with antioxidant activity, among them the mint (Mentha spicata L.) and Acerola (Malpighia glabra L.). The objective of this study was to evaluate the oxidative stability of biodiesel in the presence of natural antioxidants from extracts of Acerola and mint leaves obtained by conventional extraction and supercritical CO2 on temperature and various pressure using oxidative stability in Rancimat test, avaliou- is also the synthetic antioxidant TBHQ, to compare the results obtained with the use of the plant extracts. The effects of temperature and pressure on the yield and quality of the extract. The best induction times were obtained for biodiesel plus the supercritical extracts of Acerola 40 °C and 150 bar condition (1.38 h) and 60 °C and 250 bar (1.07 h) and the supercritical extract of mint conditions of 40 °C and 150 bar (1.08 h), 40 °C and 250 bar (1.71 h) and 60 °C and 250 bar (2.04 h) and soxhlet extract with hexane obtained from both acerola (2.84 h) and Mint (2.87 h), which showed greater induction time of the control (1.04 h). Biodiesel plus the synthetic antioxidant TBHQ got time higher induction to control and biodiesel plus extracts and from 36.95 hours. The oxidative stability of biodiesel was more increased when the extracts obtained by conventional extraction using Hexane as the solvent, which can be extracted from a larger quantity of compounds with antioxidant activity. / Biodiesel é um combustível que pode ser obtido de fontes renováveis e devido sua composição química é sensível à oxidação. Para aumentar sua estabilidade oxidativa é necessário acrescentar antioxidantes, que são compostos capazes de evitar ou retardar reações de oxidação e podem ser sintéticos ou naturais, dentre os naturais, destacam-se uma variedade de plantas com atividade antioxidante, dentre elas a Hortelã (Mentha spicata L.) e Acerola (Malpighia glabra L.). O objetivo deste trabalho foi avaliar a estabilidade oxidativa do Biodiesel na presença de antioxidantes naturais dos extratos das folhas de Acerola e Hortelã obtidos por extração convencional e com CO2 supercrítico em condições de temperatura e pressão variadas, utilizando teste de estabilidade oxidativa em Rancimat, avaliou-se, também, o antioxidante sintético TBHQ, para comparar com os resultados obtidos com a utilização dos extratos das plantas. Foram avaliados os efeitos da temperatura e Pressão no rendimento e da qualidade do extrato. Os melhores tempos de indução obtidos foram para o Biodiesel acrescido dos extratos supercríticos da Acerola nas condições 40 °C e 150 bar (1,38 h) e 60 °C e 250 bar (1,07 h) e os extratos supercríticos da Hortelã nas condições de 40 °C e 150 bar (1,08 h), 40 °C e 250 bar (1,71 h) e 60 °C e 250 bar (2,04 h) e os extratos soxhlet obtidos com hexano, tanto da Acerola (2,84 h) quanto da Hortelã (2,87 h), que apresentaram tempo de indução maior que o controle (1,04 h). O Biodiesel acrescido do antioxidante sintético TBHQ obteve tempo de indução superior ao controle e ao biodiesel acrescidos dos extratos, sendo de 36,95 horas. A estabilidade oxidativa do Biodiesel foi superior quando acrescido dos extratos obtidos por extração convencional utilizando Hexano como solvente, que, pode ter extraído uma maior quantidade de compostos com atividade antioxidante.

<p>Cilj istraživanja u ovom radu bilo je ispitivanje uticaja<br />različitih vidova ekstrakcije (konvencionalna ekstrakcija<br />organskim rastvaračem i superkritična ekstrakcija ugljendioksidom)<br />na kvalitet oleorizina začinske paprike u pogledu<br />kvalitativnog i kvantitativnog sadržaja bojenih materija,<br />sastava masnih kiselina i antioksidativnih svojstava. Po&scaron;to u<br />Vojvodini postoje značajni kapaciteti za proizvodnju i preradu<br />začinske paprike, smatramo da će rezultati ovih ispitivanja<br />dati uvid u kinetiku različitih tipova ekstrakcije i pružiti<br />informacije o uslovima potrebnim za dobijanje proizvoda<br />vrhunskog kvaliteta.</p> / <p>The aim of the work was to investigate the influence of<br />different extraction methods (conventional extraction using<br />organic solvent and supercritical carbon-dioxide extraction)<br />to qualitative and quantitative pigment content, fatty acid<br />content and antioxidant properties of oleoresins. As there<br />have been significant production and processing capacities of<br />spice pepper in Vojvodina, the results of these investigations<br />will give a closer insight into the kinetics of different types of<br />extraction and conditions for obtaining the high quality<br />product.</p>

Submitted by Marilene Donadel (marilene.donadel@unioeste.br) on 2018-11-12T22:46:53Z No. of bitstreams: 1 Elaine_Witt_2018.pdf: 2791531 bytes, checksum: 048d2ad0555e9f07d9ad80e05214ce75 (MD5) / Made available in DSpace on 2018-11-12T22:46:56Z (GMT). No. of bitstreams: 1 Elaine_Witt_2018.pdf: 2791531 bytes, checksum: 048d2ad0555e9f07d9ad80e05214ce75 (MD5) Previous issue date: 2018-09-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Biodiesel is a sensible fuel to the oxidation, because it presents in its chemical composition some free radicals. To raise its oxidative stability it is necessary to add synthetic or natural antioxidants. Among the natural antioxidants there is a variety of plants that may be used with the function to avoid or to detain the chain reactions of oxidation, which are capable to promote or inactivate the free radicals interrupting the reaction in the biofuel chain. In the pomegranate peel is possible to detect some phenolic compounds and antioxidants compounds beyond several bioactive compounds with some mechanisms of action that are similar to the vitamin C, vitamin E and beta-carotene. The aim of this study was to evaluate the biodiesel oxidative stability in the presence of some natural oxidants which were extracted from the pomegranate peel by the conventional method of extraction (Soxhlet and the grease and oils extractor – Goldfish) and by the supercritical extraction with CO2 in a condition of constant pressure (200 bar), some variation in the temperature (35, 45 and 55 oC) and in the presence of the cosolvent ethanol (0, 2,5 and 5 mL). The extracts were measured in relation to the antioxidant activity by the DPPH• radical inhibition. The extract obtained by the Soxhlet method with ethyl acetate presented 94,16% of inhibition in the 1000 µg.mL-1 concentration. The phenolic compound content was used with the FolinCiocalteu reagent, which was evaluated for the extracts. The sample obtained by the grease and oils extractor – Goldfish with an ethanol solvent, showed a density of 98,62mg of EAG/g of the extract. The commercial biodiesel was additive with some extract of the pomegranate peel and with the synthetic antioxidants BHA and BHT and submitted to the oxidative stability test in the Rancimat. A test that indicates the time of the oxidation in the Exploratory Differential Calorimetry (DSC) equipment. It was analyzed the effects in the temperature and the addition of the ethanol cosolvent in the extract yield. The best tenses of induction obtained were for the additive biodiesel with some extracts obtained by the conventional method, both with the ethyl acetate solvent, which took 11,13 hours for the extract obtained in the grease and oils extractor (ExtAcet) and 11,01 hours for the extract obtained in the Soxhlet (SoxAcet). It was checked that these values are higher than the other ones which were found for the additive biodiesel with the synthetic antioxidants BHA (6,91h) and BHT (7,86). Among the extracts obtained by the supercritical extraction, it was highlighted the condition of 35 °C with 5 mL of ethanol (8,01 h) and 55 °C with 5 mL of ethanol (7,77 h).Except the supercritical extract in the temperature of 35 oC without the addition of ethanol, all the extracts presented a time of induction higher than the obtained in the control (4,38 h), however only threeextracts that were added to the biodiesel showed a higher value which is demanded in the Resolution n45/2014 and it predicts oxidative stability of 8h for the test in Rancimat. For the DSC test, the samples that presented a higher time of oxidation were for the ExtAcet (31,42 min) and the supercritical extraction in the condition of 35 °C with 5mL of ethanol (31,25 min). The biodiesel oxidative stability was in the most part higher when it was added to thepomegranate peel in comparison to the pure biodiesel showing efficiency in its utilization as a natural antioxidant. / Biodiesel é um combustível sensível a oxidação devido a sua composição química. Para elevar sua estabilidade termo oxidativa é necessário acrescentar antioxidantes sintéticos ou naturais. Dentre os antioxidantes naturais existe uma variedade de plantas que podem ser utilizadas com a finalidade de evitar ou retardar reações de oxidação. Estes são capazes de promover ou inativar os radicais livres interrompendo a reação em cadeia de oxidação do biocombustível. Na casca de romã é possível encontrar compostos fenólicos, compostos antioxidantes além de diversos compostos bioativos, com mecanismo de ação semelhante ao da vitamica C, Vitamina E e betacaroteno. O objetivo deste trabalho foi avaliar a estabilidade oxidativa do Biodiesel na presença de antioxidantes naturais extraídos da casca da romã pelo método de extração convencional (Soxhet e extrator de óleos e gorduras-Goldfish) e pela extração Supercrítica com CO2 supercrítico em condições de pressão constante (200 bar) e variação de temperatura (35, 45 e 55 oC) e cossolvente etanol (0 mL, 2,5 mL e 5 mL). Os extratos foram avaliados quanto à atividade antioxidante pela inibição do radical DPPH•, sendo o extrato obtido pelo método Soxhlet com acetato de etila o que apresentou 94,16% de inibição na concentração de 1000 µg.mL-1. O Teor de Compostos Fenólicos utilizando o reagente FolinCiocalteu foi avaliado para os extratos e a amostra obtida pelo equipamento extrator de óleos de gorduras-Goldfish com solvente etanol apresentou uma concentração de 98,62 mg de EAG/g de extrato. O biodiesel comercial foi aditivado com os extratos de casca de romã e com os antioxidantes sintéticos BHA e BHT e submetidos ao teste de estabilidade oxidativa em Rancimat e teste para indicar o tempo de oxidação em equipamento de Calorimetria Diferencial Exploratória (DSC). Foram avaliados os efeitos da temperatura e da adição de cossolvente etanol no rendimento do extrato. Os melhores tempos de indução obtidos foram para o Biodiesel aditivado com os extratos obtidos pelo método convencional, ambos com solvente acetato de etila, sendo 11,13 horas para o extrato obetido no extrator de óleos e gorduras (ExtAcet) e 11,01 horas para o SoxAcet. Ainda verificou-se que esses valores são superiores aos encontrados para o biodiesel aditivado com os antioxidantes sintéticos BHA (6,91 h) e BHT (7,86 h). Entre os extratos supercríticos destacou-se a condição de 35 °C com 5 mL de etanol (8,01 h) e 55 °C com 5 mL de etanol (7,77 h). Com exceção do extrato supercrítico na temperatura de 35 oC sem adição de etanol, todos os extratos apresentaram um tempo de indução superior ao obtido no controle (4,38 h), no entanto apenas três extratos aditivados ao biodiesel apresentaram valor superior ao exigido pela Resolução 45/2014 a qual prevê estabilidade oxidativa de 8 horas para o teste em Rancimat. Para o teste DSC, as amostras que apresentaram maior tempo de oxidação foi para o ExtAcet (31,42 min) e extração supercrítica na condição de 35 °C com 5 mL de etanol (31,25 min). A estabilidade oxidativa do biodiesel foi, em sua maioria, superior quando acrescido dos extratos de casca de romã, em comparação ao biodiesel puro, mostrando eficiência na sua utilização como antioxidante natural.

This diploma thesis is focused on the analysis of egg yolks and egg whites from chickens raised with different breeding methods in the Czech Republic using three analytical methods. The Kjeldahl method was used to determine the proteins, the Soxhlet method was used to determine the lipids and ICP-OES was used for elemental analysis. The theoretical part describes the history of chicken breeding, marking and distribution of eggs and composition of eggs based on various aspects. The main point was the separation of egg yolk and egg white and the subsequent description on the chemical and physiological level. Principle of used methods is also described. The experimental part deals with the preparation of samples, calibration samples and process analysis. All the results of analysed substances are summarized, statistically evaluated and compared with the other literature. For this analysis were used eleven different types of eggs from the Czech Republic from six different categories.

South Africa ratified the Stockholm Convention (SC), which became legally binding on 17 May 2004. This Convention targets 12 particularly toxic persistent organic pollutants (POPs) for virtual elimination. The Convention also requires parties to reduce the release of organochlorine pesticides and the intentionally- and unintentionally-produced POPs such as dioxins, furans and polychlorinated biphenyls (PCBs) (referred to as dioxin-like chemicals). Dioxins are a heterogeneous mixture of chlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) congeners. These substances were never intentionally produced but are produced as by-products of industrial processes (such as metallurgical processes and bleaching of paper pulp). They can also be formed during natural processes such as volcanic eruptions and forest fires. The largest contributor to releases of PCDD/Fs in the environment is incomplete combustion from waste incinerators leading to the unintentional production of these compounds. Polychlorinated biphenyls (PCBs) are used in transformers and capacitors, but can also be formed unintentionally during industrial and thermal processes. Dioxin-like chemicals (PCDD/Fs and/or PCBs) are classified as persistent because of the following characteristics: lipophilicity and hydrophobicity; resistance to photolytic, chemical and biological degradation and they are able to travel long distances. As South Africa is a semiarid region, POPs will be less prone to travel here because these substances favour colder regions with high soil organic matter. Fish, predatory birds, mammals (including humans) absorb high concentrations of POPs through the process of bio-concentration, leading to bio-accumulation of these substances in the fatty tissue. PCDD/Fs occur as unwanted trace contaminants in air, water, land, in residues and products (such as consumer goods e.g. paper and textiles). The distribution of these chemicals into various matrices is problematic since they cause damage to the environment and human health. These chemicals pose a threat to human health when found in high concentrations that may lead to acute hepatoxicity and dermal toxicity (chloracne). Long-term exposure to low concentrations of these substances might lead to chronic effects such as reproductive problems and carcinogenicity. Since ferrous and non-ferrous metal production is a source of dioxin-like chemicals, a platinum mine in the Limpopo Province, South Africa, was selected for this investigation. The aim of the study was to determine if there are dioxin-like chemicals associated with platinum mining and processing, and if the H4IIE reporter gene bio-assay could be used to semi-quantify and assess the potencies of the complex environmental and process samples by determining their Toxic Equivalency Quotients (TEQ). The implications of the sources to the formation of dioxin-like chemicals regarding the SC were investigated and recommendations were made to improve this study. Samples were collected from tailings dams, woodchips, a dumpsite and slag from the smelter at Union Section. Samples were extracted with the Soxhlet apparatus using hexane as solvent. The percentage total organic carbon (%TOC) was determined for each sample to normalise the data. The method used was the Walkley-Black method. In determining the TEQ of each sample, the H4IIE luc cell line was used. The cells of the H4IIE luc line are genetically modified rat hepatoma cells stably transfected with a luciferase firefly gene. The luciferase gene is activated by the presence of dioxin-like compounds and the concentration of the enzyme is measured as relative light units (RLUs). The amount of RLUs is directly proportional to the dioxin load in the extract. This method is rapid, cost and time-effective in determining the TEQ when compared to chemical analysis. The TEQ2o-valuesin the various samples, as determined with the H4IIE luc cell line, ranged from 0.007 ngTEQ/kg to 54.06 ngTEQ/kg. Thermal processes at the smelter, sorption of hydrophobic organic compounds (HOCs) to soil and tailings, and external sources such as anthropogenic activities contributed to high TEQ2o-values. Climatic conditions, wind, precipitation, and solubility of HOCs into surfactants lead to low TEQ20. The smelter at Union Section had a very high TEQ20of 44.62 ngTEQ/kg compared to Impala Platinum mine (5.15 ngTEQ/kg). This implies that workers at Union Section are possibly exposed to low and high concentrations of dioxin-like chemicals. Long-term exposure to these compounds could lead to bio-accumulation in the fatty tissue of the mine workers, leading to chronic effects such as reproductive problems and cancer. The air emission of the furnace at the smelter was 0.03 gTEQ/annum and the release of the PCDD/Fs into the slag was 0.60 gTEQ/annum. By effectively managing the smelter it is possible to reduce the TEQ. The TEQ of each sample increased due to normalising the data. The normalised TEQ20 ranged from 0.94 ng TEQ/kg to 42497.48 ngTEQ/kg. Dioxin-like chemicals are present on a platinum mine, but at varying quantities and the effects of these compounds might be detrimental to the environment and the workers at the platinum mine. Further analyses of the health impacts associated with the platinum mine are needed. The H4IIE reporter gene bio-assay could be used to effectively determine the TEQ of each sample. Although this investigation has identified the formation and presence of dioxin-like chemicals at certain stages of mining and processing, not all of the processes were investigated. Some of these processes have the potential to add, and even destroy, these chemicals, affecting potential human exposure and amounts released to the environment. This, however, requires further investigation. The financial assistance of the National Research Foundation (NRF) towards this research is hereby acknowledged. Opinions expressed and conclusions arrived at, are those of the author and are not necessarily to be attributed to the NRF. / Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2006.

South Africa ratified the Stockholm Convention (SC), which became legally binding on 17 May 2004. This Convention targets 12 particularly toxic persistent organic pollutants (POPs) for virtual elimination. The Convention also requires parties to reduce the release of organochlorine pesticides and the intentionally- and unintentionally-produced POPs such as dioxins, furans and polychlorinated biphenyls (PCBs) (referred to as dioxin-like chemicals). Dioxins are a heterogeneous mixture of chlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) congeners. These substances were never intentionally produced but are produced as by-products of industrial processes (such as metallurgical processes and bleaching of paper pulp). They can also be formed during natural processes such as volcanic eruptions and forest fires. The largest contributor to releases of PCDD/Fs in the environment is incomplete combustion from waste incinerators leading to the unintentional production of these compounds. Polychlorinated biphenyls (PCBs) are used in transformers and capacitors, but can also be formed unintentionally during industrial and thermal processes. Dioxin-like chemicals (PCDD/Fs and/or PCBs) are classified as persistent because of the following characteristics: lipophilicity and hydrophobicity; resistance to photolytic, chemical and biological degradation and they are able to travel long distances. As South Africa is a semiarid region, POPs will be less prone to travel here because these substances favour colder regions with high soil organic matter. Fish, predatory birds, mammals (including humans) absorb high concentrations of POPs through the process of bio-concentration, leading to bio-accumulation of these substances in the fatty tissue. PCDD/Fs occur as unwanted trace contaminants in air, water, land, in residues and products (such as consumer goods e.g. paper and textiles). The distribution of these chemicals into various matrices is problematic since they cause damage to the environment and human health. These chemicals pose a threat to human health when found in high concentrations that may lead to acute hepatoxicity and dermal toxicity (chloracne). Long-term exposure to low concentrations of these substances might lead to chronic effects such as reproductive problems and carcinogenicity. Since ferrous and non-ferrous metal production is a source of dioxin-like chemicals, a platinum mine in the Limpopo Province, South Africa, was selected for this investigation. The aim of the study was to determine if there are dioxin-like chemicals associated with platinum mining and processing, and if the H4IIE reporter gene bio-assay could be used to semi-quantify and assess the potencies of the complex environmental and process samples by determining their Toxic Equivalency Quotients (TEQ). The implications of the sources to the formation of dioxin-like chemicals regarding the SC were investigated and recommendations were made to improve this study. Samples were collected from tailings dams, woodchips, a dumpsite and slag from the smelter at Union Section. Samples were extracted with the Soxhlet apparatus using hexane as solvent. The percentage total organic carbon (%TOC) was determined for each sample to normalise the data. The method used was the Walkley-Black method. In determining the TEQ of each sample, the H4IIE luc cell line was used. The cells of the H4IIE luc line are genetically modified rat hepatoma cells stably transfected with a luciferase firefly gene. The luciferase gene is activated by the presence of dioxin-like compounds and the concentration of the enzyme is measured as relative light units (RLUs). The amount of RLUs is directly proportional to the dioxin load in the extract. This method is rapid, cost and time-effective in determining the TEQ when compared to chemical analysis. The TEQ2o-valuesin the various samples, as determined with the H4IIE luc cell line, ranged from 0.007 ngTEQ/kg to 54.06 ngTEQ/kg. Thermal processes at the smelter, sorption of hydrophobic organic compounds (HOCs) to soil and tailings, and external sources such as anthropogenic activities contributed to high TEQ2o-values. Climatic conditions, wind, precipitation, and solubility of HOCs into surfactants lead to low TEQ20. The smelter at Union Section had a very high TEQ20of 44.62 ngTEQ/kg compared to Impala Platinum mine (5.15 ngTEQ/kg). This implies that workers at Union Section are possibly exposed to low and high concentrations of dioxin-like chemicals. Long-term exposure to these compounds could lead to bio-accumulation in the fatty tissue of the mine workers, leading to chronic effects such as reproductive problems and cancer. The air emission of the furnace at the smelter was 0.03 gTEQ/annum and the release of the PCDD/Fs into the slag was 0.60 gTEQ/annum. By effectively managing the smelter it is possible to reduce the TEQ. The TEQ of each sample increased due to normalising the data. The normalised TEQ20 ranged from 0.94 ng TEQ/kg to 42497.48 ngTEQ/kg. Dioxin-like chemicals are present on a platinum mine, but at varying quantities and the effects of these compounds might be detrimental to the environment and the workers at the platinum mine. Further analyses of the health impacts associated with the platinum mine are needed. The H4IIE reporter gene bio-assay could be used to effectively determine the TEQ of each sample. Although this investigation has identified the formation and presence of dioxin-like chemicals at certain stages of mining and processing, not all of the processes were investigated. Some of these processes have the potential to add, and even destroy, these chemicals, affecting potential human exposure and amounts released to the environment. This, however, requires further investigation. The financial assistance of the National Research Foundation (NRF) towards this research is hereby acknowledged. Opinions expressed and conclusions arrived at, are those of the author and are not necessarily to be attributed to the NRF. / Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2006.

Flavonoids were identified and quantified in samples of dry leaves of plant Stevia rebaudiana Bertoni. Content of flavonols (kaempherol, quercetin, myricetin, rutin) and flavons (apigenin, luteolin) were compared in three samples (standard leaves of Stevia rebaudiana Bertoni, Stevia rebaudiana Bertoni origin from Ukraine and from Czech republic), that were extracted by three extraction methods (PSE, ultrasonic extraction, Soxhlet extraction) with two polar solvents, methanol and ethanol, in combination with non-polar hexane. Extracts were analyzed by HPLC with detection UV-VIS. Antioxidant activity and total content of flavonoids in extracts were measured by spectrometry. Stable free radical DPPH. was used for determination of scavenging effect in extracts. PSE was the most effective extraction method with this conditions – 120 °C, dynamic mode and with methanol like solvent.