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1
Lawson, David R. "Chemistry and biochemistry of Solanum chacoense, bitter steroidal alkaloids /." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487843688958887.
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Mirzaee, Mehrdad. "Development of diagnostic tools to predict incidence of bitter pit during apple storage." Thesis, University of Greenwich, 2015. http://gala.gre.ac.uk/18210/.
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Bitter pit is an important physiological disorder of many apple cultivars where the low uptake and poor distribution of calcium within the cortex of apples pervades. Controlled atmosphere storage and application of 1-MCP (SmartFreshSM) can delay the onset of bitter pit symptoms by delaying maturity and senescence; however, significant losses may occur in long-term stored apples. It is hard to detect internal bitter pit using external examination alone. Previous studies have focused on improving pre-harvest prediction and curative treatments before harvest. Present prediction models are based on history of orchards, mineral analysis 2-3 weeks before harvest and quality assessments and monitoring over storage time. This study aimed to identify a greater understanding of the storage potential of fruit based on destructive standard quality assessments, biochemical and molecular analysis, also a non-destructive monitoring method by chlorophyll fluorescence at the point of harvest and monitoring during storage for developing more reliable prediction models to improve storage management. The role of free and conjugated calcium in maintaining cellular integrity and the relationship between biochemical and fluorescence changes and development of bitter pit were investigated. A diagnostic model based on comparison of changes of ascorbic acid during storage was developed. Another diagnostic model based on changes in the proportion of calcium oxalate content during storage in comparison with harvest was developed to identify samples with higher propensity to bitter pit. Also chlorophyll fluorescence was investigated as a non-destructive method for monitoring fruit during storage and prediction models for detecting changes in the maturity of fruit and developing bitter pit and reduction of fluorescence during storage as an alert to identify incidence of bitter pit were developed. Furthermore, changes in gene expression profiles of a limited number of genes like calmodulin showed the differences in patterns of transcripts between apples suffering from bitter pit and healthy apples. All the suggested methods have potential of being commercialised and applied practically to improve apple fruit store management. It would be possible to build a multi variate model for predicting the onset of bitter pit development in apple by combination of two or more suggested diagnostic tools.
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Alotaibi, Yousef. "Chemistry of humic-like substances in the atmosphere." Thesis, University of East Anglia, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405706.
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Chiwona-Karltun, Linley. "A reason to be bitter : cassava classification from the farmers' perspective /." Stockholm : [Karolinska institutets bibl.], 2001. http://diss.kib.ki.se/2001/91-7349-078-4/.
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Bostanian, Levon Artine. "Novel drug delivery systems for relatively insoluble substances /." The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu14878617968179.
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O'Loughlin, Edward John. "Association of organotin compounds with aquatic humic substances /." The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487946776023338.
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Lacroix, Pauline M. "Methods for total drug and related substances in pindolol." Thesis, University of Ottawa (Canada), 1991. http://hdl.handle.net/10393/7885.
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A liquid chromatographic method for the assay of pindolol and related compounds in the bulk drug was developed. The method resolves six known and several unknown impurities from the drug and each other using a nitrile column, a mobile phase composed of acetonitrile-sodium acetate buffer (35:65), and a UV detector set at 219 nm. Minimum quantifiable amounts of impurities are 0.02% or less relative to the drug. Ten lots of pindolol raw material were evaluated for purity and drug content. Total levels of impurities in these samples, quantitated against pindolol, ranged from about 0.03% to 0.24%. Assay results were within the range of 98.5% to 101.5%.
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Kim, Jong-Soo. "Characteristics of humic substances and their removal behavior in water treatment." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/21469.
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Gude, Michael Thomas. "Critical properties of homologous series of substances." Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/11205.
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Kumke, Michael U., and Fritz Hartmann Frimmel. "Stationary and time-resolved fluorescence for humic substances characterization." Universität Potsdam, 2002. http://opus.kobv.de/ubp/volltexte/2007/1235/.
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Steady-state and time-resolved fluorescence methods were applied to investigate the fluorescence properties of humic substances of different origins. Using standard 2D emission and total luminescence spectra, fluorescence maxima, the width of the fluorescence band and a relative fluorescence quantum efficiency were determined.
Different trends for fulvic acids and humic acids were observed indicating differences in the heterogeneity of the sample fractions. The complexity of the fluorescence decay of humic substances is discussed and compared to simple model compounds.
The effect of oxidation of humic substances on their fluorescence properties is discussed as well.
11
Baran, Ozlem. "Determination Of Narcotic And Psychotropic Substances By Using Infrared Spectroscopy." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606293/index.pdf.
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Narcotic and psychotropic substances are all chemicals that affect a person&rsquo<br>s mental activities, perceptual abilities, behavior and level of consciousness<br>they may cause physical and/or psychological dependence. For determination of narcotic and psychotropic substances, chromatographic techniques are usually preferred which are aimed to identify the target chemicals and require several extraction steps. In this study, an Infrared Spectrometric method has been developed for qualitative determination of most widely encountered substances (morphine, heroin, cocaine, MDMA (3,4-methylenedioxymethamhetamine) and amphetamine) and additives (caffeine, paracetamol and lactose). Standard reference materials and illicit samples have been analyzed in powdered form by using Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) technique. In the first part, a spectral FTIR database was constituted from the standard references. Illicit samples containing drugs and additives in varying percentages were analyzed using the same method and their database forecast results were compared with results from Gas Chromatography and High Pressure Liquid Chromatography. In the second part of the study, the possibility of finding a similarity between two samples just by comparing their spectra was investigated. For this purpose, all illicit sample spectra were collected in a new database, and then randomly selected samples were searched using this database. Most of the search attempts resulted in a correct match. Consequently, it has been observed that FTIR-ATR can be used as a priory detection step for classification studies<br>moreover with this technique pre-determination of narcotic and psychotropic substances can be done simply and rapidly.
12
Enlund, Anna Maria. "Capillary electroseparations in pharmaceutical analysis of basic drugs and related substances." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2001. http://w3.ub.uu.se/fulltext/91-554-4908-5.pdf.
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Scanlon, M. M. "Some aspects of the interaction of humic substances with metal ions." Thesis, Aston University, 1991. http://publications.aston.ac.uk/9783/.
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Humic substances are the major organic constituents of soils and sediments. They are heterogeneous, polyfunctional, polydisperse, macromolecular and have no accurately known chemical structure. Their interactions with radionuclides are particularly important since they provide leaching mechanisms from disposal sites. The central theme to this research is the interaction of heavy metal actinide analogues with humic materials. Studies described focus on selected aspects of the characteristics and properties of humic substances. Some novel approaches to experiments and data analysis are pursued. Several humic substances are studied; all but one are humic acids, and those used most extensively were obtained commercially. Some routine characterisation techniques are applied to samples in the first instance. Humic substances are coloured, but their ultra-violet and visible absorption spectra are featureless. Yet, they fluoresce over a wide range of wavelengths. Enhanced fluorescence in the presence of luminescent europium(III) ions is explained by energy transfer from irradiated humic acid to the metal ion in a photophysical model. Nuclear magnetic resonance spectroscopy is applied to the study of humic acids and their complexes with heavy metals. Proton and carbon-13 NMR provides some structural and functionality information; Paramagnetic lanthanide ions affect these spectra. Some heavy metals are studied as NMR nuclei, but measurements are restricted by their sensitivity. A humic acid is fractionated yielding a broad molecular weight distribution. Electrophoretic mobilities and particle radii determined by Laser doppler electrophoretic Light Scattering are sensitive to the conditions of the supporting media, and the concentration and particle size distribution of humic substances. In potentiometric titrations of humate dispersions, the organic matter responds slowly and the mineral acid addition is buffered. Proton concentration data is modelled and a mechanism is proposed involving two key stages, both resulting in proton release after some conformational changes.
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Moreno, Anjelica Victoria Peralez. "Modeling Atmospheric Transport of Perfluorinated Alkyl Substances from Chemours Facilities Using CALPUFF View." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555004834088189.
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Smith, Ian Derek. "Gas chromatographic studies into the stereoselective interactions of a modified cyclodextrin with enantiomeric substances." Thesis, Birkbeck (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287877.
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Shenderova, Anna. "The microclimate in poly(lactide-co-glycolide) microspheres and its effect on the stability of encapsulated substances /." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488196234910341.
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Arogba, S. S. "The synthesis and analysis of antioxidants related to the natural phenolic lipids and similar substances." Thesis, Brunel University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304767.
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Lloyd, Frances Baird Wigton. "The viscosity of mixtures of substances in aqueous solution : What do we really know?" Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/26822.
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Armitage, James M. "Modeling the global fate and transport of perfluoroalkylated substances (PFAS)." Doctoral thesis, Stockholms universitet, Institutionen för tillämpad miljövetenskap (ITM), 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-8571.
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Perfluoroalkylated substances (PFAS) are persistent contaminants that are widely distributed in the global environment. Despite the fact that these chemicals have been manufactured and used for over 50 years, there has been little scientific and regulatory interest until very recently. An important research priority over the past decade has been to gain a better understanding of the mechanisms and pathways explaining the presence of these compounds in remote regions. One explanation is related to the use and release of volatile precursor compounds which undergo atmospheric transport and are also susceptible to degradation to PFAS through gas phase reactions with radical species. The main purpose of this doctoral thesis was to investigate an alternative explanation, namely the long-range transport (LRT) of PFAS themselves, which have been released into the environment in substantial quantities during manufacturing and product use. Papers I – III explore the LRT potential of perfluorocarboxylic acids and perfluorocarboxylates and demonstrate that both oceanic and atmospheric transport are efficient pathways of dispersion from source to remote regions of the Northern Hemisphere. Oceanic transport of perfluorooctane sulfonate (PFOS) was shown to be an important process in Paper IV as well. The role of precursor transport and degradation to PFOS was also examined in this paper. The most interesting aspect of the fate and transport of PFOS precursors is the rapid response in ambient concentrations exhibited by these compounds in the model simulations following production phase-out. Since precursor compounds are known to degrade to PFOS in vivo, the modeling results demonstrate that this exposure pathway is a plausible explanation for the declining trends in PFOS concentrations reported for marine mammals in some remote environments.
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Hale, Kerry Anne. "The formation, synthesis and reactions of humic polymers in chemical and biological systems." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329937.
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Colomer, Vidal Pere. "Distribution of perfluoroalkyl substances in the environment." Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/670952.
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Perfluoroalkyl substances (PFASs) are a large group of man-made chemicals that are widely used throughout society and found in the environment. These compounds are characterized by perfluorinated carbon chains of varying lengths with hydrophobic properties and containing an external polar and hydrophilic head. The difference between perfluoroalkyl sulfonates (PFSAs) and perfluoroalkyl carboxylates (PFCAs) are found on the polar head of the chemicals. In general, the characteristics of PFASs are based on the length of the perfluorinated carbon chain that they contain. As the number of perfluorinated carbons increases in the molecule, the water solubility decreases and the better the surfactant properties, but will be more toxic for the environment due to their bioaccumulation in the organisms.
In recent years, the interest in PFASs has been growing due to their presence in humans and in wildlife species even from remote locations, which suggests a widespread global distribution of these pollutants. The highest concentration of PFASs has typically been documented in areas with direct industrial emissions. The main purpose of this Doctoral Thesis is to study the distribution and behavior of PFASs in different environmental compartments and to elucidate the interactions among them. In the first study of this Thesis, seventeen PFASs have been analyzed in the water-sediment-plant system along the Dongzhulong and Xiaoqing Rivers in China. The study area is affected by a fluoropolymer facility that belongs to the Dongyue group and is currently one of the major facilities of polytetrafluorethylene production in China. Some studies indicate a presence of PFASs in sediments and soils and these can be a source of pollution for wildlife, and humans. The second study is aimed to evaluate the environmental occurrence of PFASs
in sediments, soils, and wildlife in the marine environment surrounding the Chafarinas Islands (South Spain) and the impact on gulls. The third study that composes this Thesis is aimed to evaluate the occurrence and 10-year temporal trend of seventeen PFAS in eggs of two gull species (Larus michahellis and Larus audouinii). These species are used as bioindicators of environmental pollution of Spain.
The results of this Thesis show that the fate of the PFASs in the environment is explained by their physicochemical properties and the characteristics of the different study matrices. In freshwater systems, high amounts of PFASs in water and sediments close to the industrial discharge were detected, and concentrations decreased along the river due to dilution. In the water-sediment system, the results suggest that long-chain PFASs accumulated in sediment whereas short-chain PFASs remained in water all along the river. When including plants in the system, PFASs were taken up by plants and translocated in the different plant compartments, and the uptake mechanisms differed among plant species. Floating species show a higher concentration among plants because easily translocate long-chian PFASs direct from the water. Rooted species must compete with the sediment for PFASs uptake. Moreover, long-chain PFASs remain accumulated in the root compartment because of protein affinity while short-chain PFASs are more mobile and can be translocated to shoots. In the marine environment of the Chafarinas Islands, low levels of PFASs detected in soils, sediments, fish, and mussels reflected that the area is not directly impacted by PFASs. In this Thesis we also have estimated the bioaccumulation potential of PFASs, using gulls. We have estimated the intake based on fish-diet in gulls from Chafarinas. We observe that the release of PFOS to the egg is 4.5% of the intake and we provide the basis for using gull eggs as biomonitors. In a final study of this Thesis, we evaluated the presence of PFASs in four main gull colonies in Spain. When comparing gull colonies, eggs from the Ebro Delta and Medes Islands, both located in the North-Eastern Mediterranean Sea, had a similar distribution of PFASs, while in Chafarinas and Atlantic Islands these PFASs were present at lower concentration levels and variability. In the Ebro Delta colonies, concentrations in eggs from L. audouinni were significantly higher than those found in L. michahellis, suggesting that fish diet influences PFAS bioaccumulation. Overall, ∑PFAS decreased in the 10-year study period but for individual compounds, trends were colony-species dependant.
This thesis permits to increase the knowledge about the processes that rule the behavior of PFASs in water, sediment, soil, and biota. Also, this thesis demonstrates the advantage of performing systematic monitoring schemes to determine the presence and fate of PFASs in the environment.<br>El objetivo principal de esta Tesis Doctoral es estudiar la distribución y el comportamiento de las sustancias perfluoroalquiladas (PFASs) en diferentes compartimentos ambientales. En esta tesis se analizan diecisiete PFASs en el sistema de plantas de agua-sedimento a lo largo de los ríos Dongzhulong y Xiaoqing, en sedimentos, suelos y fauna de las Islas Chafarinas (Sur de España), y para finalizar se evalúan las tendencias temporales durante 10 años en huevos de dos especies de gaviotas consideradas bioindicadores de contaminación.
Los resultados de esta tesis muestran que la distribución de las PFASs en el medio ambiente se define por sus propiedades fisicoquímicas y las características de las diferentes matrices de estudio. En el sistema agua-sedimento, los resultados sugieren que la distribución de las PFASs depende de la longitud de la cadena. Las plantas absorben PFASs y los transfieren a diferentes compartimentos de las plantas. En el ambiente marino de las Islas Chafarinas, bajos niveles de PFASs se detectaron en suelos, sedimentos, peces y mejillones reflejando el poco impacto de estas sustancias en esa área. También se estimó el potencial de bioacumulación de las PFASs en gaviotas y se evaluó su presencia en huevos de diferentes colonias. Los huevos del delta del Ebro y de las islas Medas, ambos ubicados en el Mediterráneo nororiental, tenían una distribución de PFASs similar, mientras que en Chafarinas e Islas Atlánticas tienen a niveles de concentración muy bajos. En las colonias del Delta del Ebro, las concentraciones en huevos de L. audouinni fueron significativamente más altas que las encontradas en L. michahellis debido a diferencias en la dieta. En general, la concentración ∑PFASs disminuyó en el período de estudio, pero para los compuestos individuales las tendencias dependían de las colonias y especies.
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Skerlj, Renato Tony. "Synthesis and chemistry of alkyl 2, 3-bis(trimethylstannyl)-2-alkenoates and related substances." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/29391.
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This thesis describes the synthesis and chemistry of alkyl 2,3-bis(trimethylstannyl)-2-alkenoates ((78) and (83)). It was shown that these compounds could be readily transformed into useful intermediates for the synthesis of functionalized, stereochemically defined tetrasub-stituted alkenes (87) and tricyclic dienes of general structure (322A).
The synthesis and chemistry of compounds (277) and (278) is also described.
The palladium(O)-catalyzed addition of hexamethylditin to a variety of α,β-acetylenic esters (90), afforded in a stereoselective manner, the corresponding alkyl (Z)-2,3-bis(trimethylstannyl)-2-alkenoates (83). Subsequent thermolysis of these compounds afforded the corresponding alkyl (E)-2 , 3-bis(trimethylstannyl)-2-alkenoates (78).
It was found that treatment of alkyl (E)- and (Z)-2,3-bis(tri-methylstannyl)-2-alkenoates with methyllithium at low temperature, followed by reaction of the resultant nucleophilic intermediate with a variety of alkylating agents, afforded the trisubstituted vinylstannanes (80). On the other hand, successive treatment of methyl w-halo-2,3-bis-(trimethylstannyl)-2-alkenoates (202) with methyllithium and HMPA provided a facile route to cyclic β-trimethylstannyl α,β-unsaturated esters (203).
Compounds (80) were readily converted into vinyl iodides of general structure (219) in which W is a functionalized group derived from the CO₂R moiety. These latter compounds served as useful intermediates for the synthesis of functionalized, stereochemically defined tetrasubstituted alkenes (87). For example, treatment of compounds (219) with 1.1 or 2.2 equiv of n-butyllithium at -78°C afforded the corresponding vinyllithium species (86) , which could either be alkylated directly or further transposed into the organocopper(I) reagent (263A) and then alkylated, to afford in each case, the tetrasubstituted alkenes (87).
The Pd(0)-catalyzed addition of tri-n-butylstannyltrimethylgermane (276) to a variety of α,β-acetylenic esters (90) afforded the corresponding
compounds (277) and (278) in a ratio of approximately 3:1, respectively. Treatment of the (E) isomers (277) with n-butyllithium at -98°C, followed by alkylation of the resultant nucleophilic intermediate afforded the corresponding trisubstituted vinylgermanes (293). One of these latter compounds was readily converted into the iodo bromide (308), which is potentially synthetically equivalent to the d,a synthon (310).
When the enolate anion of compounds (203) was successively treated with HMPA and compound (308) the esters (311) were obtained. The Pd(0) catalyzed intramolecular coupling of the vinylstannane-vinyl iodide moieties of (311) provided a facile route to the bicyclic triene esters (312). Similarly, alkylation of the enolate anion of compounds (203) with (325) (which was readily obtained from (203), in which n - 1), followed by the Pd(0)-catalyzed coupling of the resulting alkylated material afforded the tricyclic diene esters (322A). [Formula Omitted]<br>Science, Faculty of<br>Chemistry, Department of<br>Graduate
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Kumke, Michael U., and Sascha Eidner. "Fluorescence and energy transfer processes of humic substances and related model compounds in terbium complexes." Universität Potsdam, 2005. http://opus.kobv.de/ubp/volltexte/2007/1225/.
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The fluorescence properties and the fluorescence quenching by Tb3+ of substituted benzoic acid were investigated in solution at different pH. The substituted benzoic acids were used as simple model compounds for chromophores present in humic substances (HS). It is shown that the fluorescence properties of the model compounds resemble fluorescence of HS quite well. A major factor determining the fluorescence of model compounds are proton transfer reactions in the electronically excited state. It is intriguing that the fluorescence of the model compounds was almost not quenched by Tb3+ while the HS fluorescence was decreased very effectively. From our results we concluded that proton transfer reactions as well as conformational reorientation processes play an important role in the fluorescence of HS. The luminescence of bound Tb3+ was sensitized by an energy transfer step upon excitation of the model compounds and of HS, respectively. For HS the observed sensitization was dependent on its origin indicating differences 1) in the connection between chromophores and
binding sites and 2) in the energy levels of the chromophore triplet states. Hence, the observed sensitization of the Tb3+ luminescence could be useful to characterize structural differences of HS in solution.
Interlanthanide energy transfer between Tb3+ and Nd3+ was used to determine the average distance R between both ions using the well-known formalism of luminescence resonance energy transfer. R was dependent on the origin of the HS reflecting the difference in structure. The value of Rmin seemed to be a unique feature of the HS. It was further found that upon variation of the pH R also changed. This demonstrates that the measurement of interlanthanide energy transfer can be used as a direct method to monitor conformational changes in HS.
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Kwon, Deokhyeon. "Optical and physicochemical properties of secondary organic aerosol and aerosol generated from humic substances." Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6455.
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A great deal of attention has been paid to brown carbon aerosol in the troposphere because it can both scatter and absorb solar radiation, thus affecting the Earth’s climate. However, knowledge of the optical and chemical properties of brown carbon aerosol is still limited. In this thesis, we have investigated different aspects of the optical and physicochemical properties of various brown carbon aerosol samples of potential atmospheric importance.
First, reactions involving the di-carbonyl species methylglyoxal (MG) have been previously suggested as an important pathway for the production of secondary organic aerosol (SOA) in the atmosphere. Reaction in an aqueous inorganic salt solution, such as ammonium sulfate (AS), leads to the formation of light-absorbing brown carbon (BrC) product. In this thesis work, we employed a variety of experimental approaches to investigate the optical and physicochemical properties of BrC aerosol generated from this AS-MG reaction (BrC (AS/MG)). Optical properties of the dried BrC (AS/MG) aerosol particles were studied by Fourier transform infrared (FTIR) extinction spectroscopy in the mid-infrared region, cavity ring-down spectroscopy (CRDS) at 403 nm in the visible, and by measuring the light scattering phase function and polarization profiles at two different visible wavelengths, 532 and 402 nm. In addition, we used UV−vis spectroscopy to measure the mass absorption coefficient (MAC) of the solution-phase reaction products. The different optical properties were measured as a function of reaction time for a period of up to 22 days. The UV-vis absorption spectra showed a clear increase in measured MAC in the visible and near UV as the solution aged. However, analysis of the light scattering data showed no significant differences between AS and BrC aerosol in the derived refractive indices at either 532 or 402 nm, even for the longest reaction times. The FTIR extinction spectra was modeled in a Mie theory simulation to derive the complex refractive index in the mid-IR range (7000-800 cm−1); the results showed no significant changes in either the real or the imaginary parts of the refractive indices for BrC (AS/MG) aerosol particles when compared to unreacted AS aerosol. From the CRDS extinction data, the optical constants for BrC (AS/MG) particles at 403 nm were also determined through a Mie theory based analysis. The retrieved real index of refraction at 403 nm is n = 1.551 ± 0.005, with an imaginary index value of k = 0.000 ± 0.002; these values do not appear to change significantly with aging time over the course of 22 days and are not markedly different from the AS aerosol values. The small imaginary index value suggests that BrC (AS/MG) aerosol formed from this pathway may not significantly contribute to warming. In addition, CRDS measurements of the BrC (AS/MG) aerosol extinction at 403 nm as a function of particle size show a significant deviation from Mie theory simulations for particles with diameters of ≳500 nm, probably as a result of non-spherical particle shape effects. We also employed atomic force microscopy (AFM)-based IR spectroscopy to investigate the morphology and chemical composition of single SOA particles. AFM analysis of the particle morphology shows that a significant fraction of BrC (AS/MG) particles with diameters of ≳500 nm are non-spherical in shape, consistent with our observed breakdown in the applicability of Mie theory for larger particles. In addition to these measurements, we have characterized additional physicochemical properties of the BrC (AS/MG) aerosol particles including hygroscopic growth using a tandem-differential mobility analyzer. Compared to AS, BrC aerosol particles are found to have lower deliquescence relative humidity (DRH), efflorescence relative humidity (ERH), and hygroscopic growth at the same relative humidity values.
Second, we investigated the optical properties of the water soluble products of limonene BrC generated from ozonolysis of d-limonene with further aging by AS. Optical constants for the dried limonene BrC aerosol product were measured at 403 nm by CRDS over the course of 9 days of aging. While the fresh limonene BrC aerosol showed a significant non-zero absorption index, the aged samples showed absorption index values consistent with zero. This result was somewhat unexpected because UV-vis absorption spectra of the bulk reaction solution showed a continued increase in absorption as the solution aged. One possible explanation for this result is that there could be an increase in the fraction of volatile chromophores as the solution ages, that are then removed in the aerosol drying process.
Third, we investigated optical properties and chemical compositions of several humic substance (HS) reference samples including humic acid (HA) and fulvic acid (FA) standards by CRDS, UV-vis spectroscopy, elemental analysis, and 13C NMR spectroscopy. Measurements of the optical properties of HS is important in atmospheric science, because it is thought that HS samples have similar optical properties to organic materials, such as HUmic-Like Substances (HULIS), that exist in clouds, fogs, rainwater, and atmospheric aerosol. The humic acid aerosol samples generally showed higher absorption index values than the fulvic acid aerosol samples. We also found a correlation between the absorption index and chemical composition, with the value for k generally increasing with both increasing carbon-to-oxygen atomic ratio and sample aromaticity. In addition, we compared our measured optical constants for the HS aerosol samples with results from previous studies of field collected HULIS. The absorption index values for the fulvic acid aerosol samples give a better match than the humic acid samples when compared to the results from the field collected samples.
Overall, these studies provide new details of the optical and physicochemical properties of a class of brown carbon organic aerosol which may have important implications for atmospheric chemistry and climate.
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Gonzalez, Raymat Hansell. "Unrefined Humic Substances as a Potential Low-cost Remediation Method for Groundwater Contaminated with Uranium in Acidic Conditions." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3864.
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Anthropogenic activities such as uranium mining and milling, nuclear weapons production, and nuclear reprocessing have left a legacy of groundwater and soil contaminated with uranium that needs to be addressed. Therefore, developing new remediation technologies to sequester uranium in situ is crucial. The objective of the study was to determine if low-cost commercially available unrefined humic substances, such as Huma-K, can be used to facilitate uranium sorption to minerals in soil and sediment. Sediments from the saturated zone beneath the F-Area seepage basins at the Savannah River Site (SRS) in South Carolina were used for the present study. The SRS site is analogous to many contaminated locations where groundwater acidity enhances uranium and other contaminants mobility.
First, a variety of techniques were applied to characterize Huma-K and SRS sediment. Characterization studies showed that Huma-K possesses functional groups that have an acidic nature such as carboxyl and phenol groups. For SRS sediment, a mineral composition of mainly quartz (93.2%), kaolinite (5.1%), and goethite (1.1%) was identified.
Second, the interactions between Huma-K and SRS sediment were investigated through batch experiments. Sorption, homogeneous precipitation, and surfaced-induced precipitation were observed to be enhanced at pH 4. However, Huma-K removal from solution decreased with an increase of pH. The sorption behavior was not able to be described by any of the models employed (pseudo-first, pseudo-second, Langmuir, and Freundlich).
Third, the interactions between uranium and SRS sediment with and without Huma-K amendment were investigated. In acidic conditions (pH 3-5), the sorption capacity of SRS sediment amended with Huma-K was significantly increased compared to plain sediment. At circumneutral conditions, uranium removal from solution decreased for SRS sediment amended with Huma-K, compared with plain sediments, likely as a result of the formation of aqueous uranium-humic complexes. In summary, the results from the present study suggest that Huma-K, and likely other unrefined humate products, has the characteristics and effects necessary to be suitable for subsurface injection to remediate uranium in acidic groundwater conditions. The treatment zone will persist as long as the pH does not increase sufficiently to cause soil-bound Huma-K to be released, remobilizing uranium.
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Emenike, Mary Elizabeth. "What is a Chemical? Fourth-Grade Children's Categorization of Everyday Objects and Substances." Miami University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=miami1283196816.
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Amirkhani, Ardeshir. "Development of Techniques and Methods for the Quantitative Analysis of Endogenous Substances by Microcolumn Liquid Chromatography Coupled to Mass Spectrometry." Doctoral thesis, Uppsala University, Analytical Chemistry, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3990.
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<p>Liquid chromatography-mass spectrometry (LC-MS) is a powerful technique for the analysis of endogenous compounds. The introduction of electrospray ionization (ESI) as an interface between LC and MS has contributed strongly to a trend towards miniaturization of LC, due to the possibility to perform ESI at low flow rates. In this thesis, several aspects regarding the design of miniaturized LC systems and electrospray emitters were investigated. In addition miniaturized LC-ESI-MS have been used for the qualitative and quantitative analysis of endogenous polar compounds, peptides and protein digests. </p><p>The performance of miniaturized LC-MS was compared using different electrospray emitter configurations. The results indicated that the efficiency of the LC system is rather independent of the configuration of the emitter. </p><p>The lifetime of gold-coated fused silica electrospray emitters based on vapor deposited adhesion layers of titanium were investigated. The long lifetime of the emitter facilitates the use in LC-MS experiments, exemplified LC-MS by analysis of neuropeptides.</p><p>The ESI voltage is shown to interfere with liquid chromatographic separations performed in packed porous graphitic carbon capillary column. This interference is ascribed to the presence of an electric field over the conductive column in absence of a ground point between the column and the ESI emitter.</p><p>The solid supported enhanced microdialysis for analysis of neuropeptides were compared with conventional microdialysis. The difference between the two methodologies were evaluated by LC-MS analysis of the microdialysates. The solid supported method gave in general higher relative recoveries.</p><p>Finally, a method of standard addition was developed to determine total level of tryptophan and two of its metabolites in human plasma by capillary LC-ESI tandem mass spectrometry. The method was applied in a clinical study of multiple scleroses patients treated with cytokines (IFN Beta 1a, 1b). The results show that the intervention effects the tryptophan metabolism.</p>
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Mulaudzi, Ludwig Vusimuzi. "Application of flow injection in the assay of selected substances in food and clinical analysis." Diss., Pretoria : [s.n.], 1999. http://upetd.up.ac.za/thesis/available/etd-11162006-163430/.
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Murrell, Ruth Dorothy. "The effects of non-ionic anaesthetic substances on voltage-activated and acetylcholine-activated ion channels." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293762.
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Seither, Joshua Zolton. "Application of High Resolution Mass Spectrometry for the Screening and Confirmation of Novel Psychoactive Substances." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3823.
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There has been an emergence of novel psychoactive substances (NPS) in forensic casework globally. Although the reported prevalence of these compounds has been relatively low in comparison to traditional drugs of abuse, published case studies suggest that some NPS have significant pharmacological effects that may cause severe impairment and/or death. Because of these effects, it is important that toxicology laboratories have the capability of identifying these compounds to complete a comprehensive toxicological analysis for human performance and post-mortem investigations.
Recently, mass spectrometry has gained favor over traditional screening assays such as immunoassays for the identification of NPS in biological specimens. This trend is mainly a result of the fact that mass spectrometry provides the required sensitivity and selectivity for a broader range of analytes. High resolution tandem mass spectrometry has been suggested for analysis of NPS, as this technique further increases selectivity by increasing mass accuracy and providing MS/MS spectral data. The main goal of the present study was to investigate the applicability of using high resolution mass spectrometry to screen for and confirm a large number of novel psychoactive substances. The present study consisted of three main tasks, which included 1) the creation of a large high resolution MS/MS spectral library and database, 2) the development of a solid phase extraction (SPE) method and acquisition methods, and 3) a collision induced dissociation (CID) study of regioisomeric NPS compounds.
The MS/MS spectral library created contains spectral data for 252 NPS. In addition, 875 NPS entities were included in the compound database. The library and database can be used by toxicology laboratories to aid in the identification of NPS in casework using MS/MS spectral data and full scan MS data, respectively. The analytical method developed used SPE and high resolution mass spectrometry (HRMS). The HRMS method demonstrated limits of detection ranging from 0.5- 5 ng/mL for NPS from various structural drug classes. The CID experiments demonstrated that relative ion abundance alone could be used to differentiate some sets of regioisomers. The present work can aid toxicology laboratories in the identification of NPS and demonstrates the applicability of HRMS for their screening and confirmation.
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Alessio, Rachael Josephine. "Removal of Bisphenol A Model Compounds and Related Substances Using Octolig®." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/3946.
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Bisphenol A used in the production of polycarbonate plastics and epoxy resins is ubiquitous in the environment. The raw material is released to the environment during the manufacturing process and by leaching from consumer products. Recent studies are suggesting that low-dose amounts of Bisphenol A may have adverse health effects on humans. The possibility of removing Bisphenol A from natural water sources or from solvents used to extract the material from consumer products before they enter the market has been studied. The use of model compounds and related substances (4-isopropylphenol, 4-(t-butyl) phenol, and nitrophenols) have been used to study their removal from aqueous solutions using column chromatography and Octolig®, a commercially available material with polyethylenediamine moieties covalently bonded to high-surface area silica gel. The experimental results suggest that 2-nitrophenol and 4-nitrophenol can be successfully removed while 3-nitrophenol, 4-isopropylphenol, and 4-(t-butyl) phenol did not yield a high percent removal. A look at the pKa of the compounds provides an interesting explanation of the results. It is suggested that the compounds with a pKa of approximately 8.3 or higher would require the solution to be at a high pH for anion formation. The resulting pH of the solution would simultaneously deprotonate the ethylenediamine moieties of Octolig® rendering it incapable of removing the anions by ionic interaction.
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Gwak, Seongshin. "Comprehensive Analysis of Emerging New Psychoactive Substances by Ion Mobility Spectrometry and Mass Spectrometry." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2291.
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In the new era of drug abuse, the proliferation of new psychoactive substances (NPS), commonly referred to as designer drugs or legal highs, has been a global concern. These substances are produced to circumvent current legislation for controlled substances with minor modifications in their chemical structure. Although many efforts have been made previously, the characterization of such substances are still challenging because of (1) the continual emergence of newly identified substances, (2) the lack of a universal screening test for NPS that are structurally similar to each other, and (3) the complex and time-consuming chromatographic techniques currently used. Therefore, it is necessary to develop novel analytical methods that can be readily adapted by forensic laboratories to overcome these challenges.
In this dissertation, various analytical techniques have been evaluated for qualitative analysis of these emerging NPS. For rapid screening purposes, a commercial ion mobility spectrometry with a 63Ni ion source (63Ni-IMS) and also direct analysis in real time coupled to a quadrupole time-of-flight mass spectrometer (DART-QTOF-MS) were investigated first. The results showed that rapid detection by 63Ni-IMS and identification by DART-QTOF-MS can be achieved with sub-nanogram detection capability and high speed total analysis time less than two minutes. In recent developments of gas chromatography mass spectrometry (GC-MS), gas chromatography (GC) has been coupled to state-of-the-art mass spectrometers, including triple quadrupole (MS/MS) and quadrupole time-of-flight (QTOF). It was revealed that the application of GC-MS/MS and GC-QTOF facilitates the unambiguous identification of emerging NPS with a chemical ionization (CI) source. In addition, constitutional isomers of NPS were differentiated with the capabilities of product ion scan and multiple reaction monitoring (MRM) modes. Finally, the coupling of IMS with a mass spectrometer (IMS-MS) was investigated as an alternative confirmatory technique. With the development of an optimal solvent system in the electrospray ionization (ESI) process, the rapid analysis and identification of synthetic cathinone was successfully achieved less than five minutes. As a proof-of-concept, seized drugs samples provided by a local forensic laboratory were analyzed using these developed methods by various analytical techniques. The results from these seized samples are also presented in this evaluation.
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Eckberg, Melanie N. "Forensic Toxicological Screening and Confirmation of 800+ Novel Psychoactive Substances by LC-QTOF-MS and 2D-LC Analysis." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3923.
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Novel psychoactive substances (NPS) represent a great challenge to toxicologists due to the ability of illicit drug manufacturers to alter NPS chemical structures quickly and with ease to circumvent legislation regulating their use. Each time a new structure is introduced, there is a possibility that it has not been previously recorded in law enforcement or scientific databases. Many toxicology laboratories use targeted analytical methods that rely on libraries of known compounds to identify drugs in samples. However, these libraries do not include large numbers of NPS which could result in non-identification or detection.
High-resolution mass spectrometry (HRMS) has been suggested as a method for screening a wide variety of analytes due to its higher sensitivity and mass accuracy as compared to some other forms of mass spectrometry. This technique can generate characteristic MS/MS spectral data for use in compound identification. The main goal of this research was to create a high-resolution mass spectrometry (HRMS) library of NPS and metabolites, as well as validate a method for screening and confirmation of these substances. The study consisted of three main tasks which included; the development of a large high-resolution MS/MS spectral library and database, validation of a method for screening and confirmation of over 800 NPS and metabolites, and screening of blind-spiked and authentic urine specimens to determine real-world applicability of the HRMS library and method.
During validation, several isomeric and structurally related NPS were observed which could not be adequately separated using traditional LC methods. A fourth task was therefore added to investigate improved separation using two-dimensional liquid chromatography (2D-LC). Increased resolving power is achieved in 2D-LC through the coupling of multiple orthogonal separation systems. Ultimately, an on-line, comprehensive method was developed using orthogonal reversed-phase columns in each dimension (RP x RP) for improved separation of co-eluting and isomeric synthetic cannabinoids.
This work can aid laboratories in the identification of NPS through the use of a validated LC-QTOF-MS method for screening and confirmation and HRMS spectral library. In instances where isomeric and structurally related NPS are not sufficiently separated, RP x RP methods can be explored.
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Dalton, Rebecca Marie. "The development of students' mental models of chemical substances and processes at the molecular level /." View thesis, 2003. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20050721.160759/index.html.
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Thesis (Ph.D.) -- University of Western Sydney, 2003.<br>"A thesis submitted in fulfilment of the requirements for the award of the degree Doctor of Philosophy from University of Western Sydney" Bibliography : leaves 483-501.
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Dalton, Rebecca Marie, University of Western Sydney, of Science Technology and Environment College, and of Science Food and Horticulture School. "The development of students' mental models of chemical substances and processes at the molecular level." THESIS_CSTE_SFH_Dalton_R.xml, 2003. http://handle.uws.edu.au:8081/1959.7/816.
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The development of student’s mental models of chemical substances and processes at the molecular level was studied in a three-phase project. Animations produced in the VisChem project were used as an integral part of the chemistry instruction to help students develop their mental models. Phase one of the project involved examining the effectiveness of using animations to help first-year university chemistry students develop useful mental models of chemical phenomena. Phase two explored factors affecting the development of student’s mental models, analysing results in terms of a proposed model of the perceptual processes involved in interpreting an animation. Phase three involved four case studies that served to confirm and elaborate on the effects of prior knowledge and disembedding ability on student’s mental model development, and support the influence of study style on learning outcomes. Recommendations for use of the VisChem animations, based on the above findings, include: considering the prior knowledge of students; focusing attention on relevant features; encouraging a deep approach to learning; using animation to teach visual concepts; presenting ideas visually, verbally and conceptually; establishing ‘animation literacy’; minimising cognitive load; using animation as feedback; using student drawings; repeating animations; and discussing ‘scientific modelling’.<br>Doctor of Philosophy (PhD)
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Ingvarsson, Sarah. "Characterization of hepatocyte derived metabolites of various New Psychoactive Substances using LC-QTOF-MS." Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-167499.
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New psychoactive substances are becoming increasingly common in many parts of the world, and some of them are marketed as “legal highs” and are produced to circumvent the drug legislation, and they come in many unregulated forms. The aim of this research was to characterize the metabolites of a new psychoactive substance and hence provide the fundamental data needed for further research of toxicity and future drug testing. The synthetic cannabinoid 4-fluoro-CUMYL-5-fluoro-PICA was incubated in cryopreserved hepatocytes for 1, 3 and 5 hour and then the formed metabolites was analyzed with an LC-QTOF-MS method, data analysis was performed by using the software MassHunter Qualitative Analysis. For 4-fluoro-CUMYL-5-fluoro-PICA a total of ten metabolites were identified, with three hydroxylations, two oxidative defluorinations to carboxylation, three oxidative defluorination and two fluoropentyl dealkylation. The metabolite with the highest intensity was oxidative defluorination.
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Davis, Christina Clarkson. "Aqueous Silica in the Environment: Effects on Iron Hydroxide Surface Chemistry and Implications for Natural and Engineered Systems." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/33948.
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Aqueous silica is present in all natural waters and exhibits a high affinity for the surfaces of iron oxides. Therefore, it is expected to play an important role in environmental systems. Experiments were conducted to investigate the fundamentals of silica sorption onto pre-formed ferric hydroxide at pH 5.0-9.5 and silica concentrations of 0-200 mg/L as SiO<sub>2</sub>. Over the entire pH range studied, sorption densities exceeding monolayer sorption were observed at silica levels typical of natural waters. Under some circumstances, sorption exceeded a monolayer while the particle zeta potential remained positive, a phenomenon which is inconsistent with available models. To address this deficiency, an extended surface complexation model was formulated in which soluble dimeric silica sorbs directly to iron surface sites. This model fits sorption density data up to 0.40 mol SiO<sub>2</sub>/mol Fe, and it accurately predicts trends in zeta potential and the observed H<sup>+</sup> release during silica sorption to ferric hydroxide at pH 5.0 and 6.0.
<p>
A second phase of research was aimed at identifying the practical implications of silica sorption to iron hydroxide in natural and engineered systems. Two types of surfaces were prepared by exposing pre-formed Fe(OH)<sub>3</sub> to aqueous silica (0-200 mg/L as SiO<sub>2</sub>) for periods of 1.5 hours or 50 days. The concentration of pre-formed iron passing through a 0.45 micron pore size filter at pH 6.0-9.5 increased as the solids aged in the presence of silica. Consistent with formation of small, stable colloids, "soluble" iron concentrations exceeded 0.2 mg/L only at zeta potentials <span style="text-decoration:underline"><</span> -15 mV. When arsenate was added to iron hydroxide particles equilibrated with silica for 1.5 hours, percentage arsenate removals were high. In contrast, arsenate removals decreased markedly as pH and silica concentrations increased if silica was pre-equilibrated with the iron for 50 days. Trends in percentage removal of humic substances were similar. Competition for sorption sites was the main cause of hindered anionic contaminant removal. However, interference with hydrolysis and precipitation are expected to be important under some circumstances, particularly during water treatment.<br>Master of Science
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Chorier, Émilie. "Mise au point de méthodes d’analyse de substances critiques potentiellement présentes dans les produits et procédés de la filière cuir." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10046.
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Ce travail décrit la mise au point de onze nouvelles méthodes analytiques répondant aux exigences règlementaires REACh et à la protection des consommateurs. La première méthode permet de doser des substances dangereuses dans l’eau (RSDE) et en milieu polaire. Un protocole d’extraction unique du milieu aqueux qui permet de doser 75 substances prioritaires dans les eaux douces et résiduaires. Six méthodes instrumentales différentes sur des appareils aux caractéristiques diverses ont été associées pour obtenir des résultats beaucoup plus précis que ce qui se faisait auparavant et près des deux tiers des substances du groupe RSDE ont été analysées pour la première fois. Toutes les limites de quantification sont conformes aux exigences de la Directive Cadre Eaux ou d'autres normes Européennes. L'une des six méthodes permet d'établir précisément l’indice d’hydro– carbures volatils dans les eaux. Ce calcul n’était pas possible au laboratoire auparavant. Il s'appuie sur la méthode par espace de tête statique couplée à une analyse GC-FID/MS . La limite de quantification à 30 μg/L remplit facilement les exigences des normes françaises et européennes. Une autre nouvelle méthode analyse les résidus médicamenteux dans les eaux. Un couplage LCMS/ MS a été initié et une grande partie du travail de développement a été réalisé sans permettre une finalisation complète de la méthode en termes de fiabilité et robustesse. La septième méthode s'intéresse à 27 substances préoccupantes issues de l’annexe XIV de REACh qui peuvent maintenant être quantifiées de façon robuste et fiable et aux teneurs réglementaires de 0,1% en masse, soit 1000 mg/kg ou moins, par couplage de la GC à la spectrométrie de masse (MS). C'est encore la technique GC qui a été mise en oeuvre pour quantifier les composés organiques volatils (COV) dans les cuirs et les textiles. Certains de ces COV figurent dans le règlement REACh ou dans la norme sur la sécurité des jouets. La méthode originale développée couple la technique d’introduction des composés dite espace de tête ou headspace (HS) en anglais à un appareil HS-GC couplé à la MS. 28 molécules volatiles membres des COV préoccupants peuvent être quantifiées à 2,5 mg/kg. La chromatographie en phase liquide (HPLC) est utilisée pour les neuf et dixième méthodes mises au point. L'une traite des retardateurs de flamme phosphatés analysables dans les cuirs et textiles. Neuf de ces composés sont maintenant analysable par le laboratoire par HPLC-MS /MS avec validation avec une limite de quantification à 5 mg/kg, exception faite de l’oxyde de triaziridinyl phosphine (TEPA) dans le cuir. L'autre méthode est une amélioration d’une méthode existante HPLC-DAD pour la détermination des agents de conservation biocides dans le cuir. La récente technique UHPLC-DAD a permis une analyse de qualité équivalente dans un temps réduit trois fois et utilisant beaucoup moins de solvants. La limite de quantification associée est conforme : à 20 mg/kg pour les quatre biocides étudiés. La onzième et dernière méthode développée permet de déterminer des polluants halogénes par GC-MS/MS<br>Pas de résumé anglais
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Graf, Phoebe [Verfasser], and Martin [Akademischer Betreuer] Dameris. "The impact of very short-lived substances on the stratospheric chemistry and interactions with the climate / Phoebe Graf ; Betreuer: Martin Dameris." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2017. http://d-nb.info/113347893X/34.
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Da, Silva Pierre. "Une histoire de la recherche de substances naturelles à activités thérapeutiques." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2013. http://tel.archives-ouvertes.fr/tel-01038036.
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L'identification d'une substance naturelle, produite par un organisme vivant n'est que l'une des toutes premières étapes du développement d'un nouveau médicament. Beaucoup de molécules à visée thérapeutique développées par des sociétés pharmaceutiques ont en fait été découvertes dans des laboratoires académiques. C'est toujours un continuum de la recherche fondamentale vers la recherche appliquée, souvent de la recherche publique vers la recherche privée, qui aboutit à la mise au point d'un médicament. Leur fabrication, directement à partir de substances naturelles, pose fréquemment le problème de l'approvisionnement en matière première. De nombreuses équipes du monde entier se heurtent aux difficultés de synthèse de ces molécules naturelles complexes. Ce travail de thèse retrace l'histoire des travaux majeurs sur la recherche de molécules naturelles d'intérêt médical à travers les succès et les échecs de chercheurs ayant mis leur énergie, leur imagination, leur ténacité et leur patience au service de la science pour surmonter les obstacles et découvrir de nouvelles molécules de grand intérêt thérapeutique. Elle présente également un travail complémentaire de mise au point d'une base de données regroupant un certain nombre de plantes utiles dans la lutte contre le cancer dans le cadre d'un projet de vulgarisation scientifique. La discussion est consacrée à la question de la place du hasard dans les découvertes scientifiques à travers l'exemple de Pierre Potier.
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Liao, Jin. "Bromine and chlorine chemistry in the Arctic boundary layer." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45932.
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Halogen chemistry plays an important role in spring time ozone and mercury depletion events (ODEs and MDEs) and may efficiently oxidize hydrocarbons such as the important greenhouse gas methane (CH4) in the polar marine boundary layer. This thesis presents a detailed study of bromine and chlorine chemistry in the Arctic boundary layer based on measurements of bromine and chlorine containing species using chemical ionization mass spectrometry (CIMS). The capability of CIMS to accurately measure bromine oxide (BrO) was demonstrated. The first direct measurements of hypobromous acid (HOBr) were achieved. Conditions that likely favor bromine activation (e.g. high wind speeds) was presented. To advance the understanding of bromine recycling, a time dependent model was built to simulate the bromine speciation. Unexpected high levels of molecular chlorine (Cl2) were observed at Barrow, AK, which had a large impact on methane oxidation and could contribute to ozone loss and mercury oxidation at Barrow, AK. Moreover, BrO levels observed at Summit, Greenland did not explain the under prediction of hydroxyl radical (OH). However, the enhanced OH was found to be coincident with elevated reactive gaseous mercury (RGM). In addition, airborne BrO measurements were found to be generally consistent with airborne observations of soluble bromide based on the response factors of mist chamber to the bromine species and bromine chemical mechanisms.
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Bevin, Anna, An Na Lay, Daniel Ullmark, and Jessika Hagman. "Chemical analysis of hazardous substances in permanent tattoo inks available on the market." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-277104.
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As permanent tattoos are becoming more popular and common, an increased number of allergic reactions to tattoos is reported. The purpose of this project was to analyze tattoo inks for hazardous substances, and whether they comply to current Swedish and European legislative requirements. The tattoo inks were qualitatively analyzed for pigments, and quantitatively analyzed for metals. A total of 73 tattoo inks were collected from various sources such as a tattoo ink supplier, online retailers, and provided directly from tattoo artists. The labels of each tattoo ink bottle were inspected to investigate their compliance with the Council of Europe and the Swedish Medical Products Agency. Matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-ToF-MS) was used to qualitatively analyze 20 selected tattoo inks for different pigments. Inductively coupled plasma mass spectrometry (ICP-MS) was used to quantitatively analyze trace metals in 70 of the samples. A large majority (90%) of the tested samples violated the requirements and criteria in the European resolution ResAP 2008(1), such as information on name and address of the manufacturer, minimum date of durability, sterility, batch number, and storage. Patch and allergy testing were incorrectly recommended for many samples in a way that is not accepted by dermatologists. In a worst-case scenario, this testing could be a sensitizing step. Also, it can not prevent future allergic reactions from occurring or provide any juridical insurance. Only one brand, World Famous, fulfilled the requirements for labeling for six of the seven samples (one sample failed due to a faulty declared pigment). The brands Tang Dragon and Dynamic did not fulfill any of the requirements listed in ResAP 2008(1). The list of ingredients was incorrect for all samples from Tang Dragon (bought prior to 2019 online). Also, six of the other 50 samples from different brands (World Famous, Intenze, Fusion Tattoo Ink, Eternal Ink, Solid Ink) declared at least one pigment incorrectly in their ingredients list. 25% of the declared and theoretically detectable pigments were detected by means of MALDI-ToF-MS, whereas the other pigments were either absent or below the limit of detection. Future analyses should include an MS/MS analysis. Polyethylene glycol (PEG) was identified qualatively in 15 of the 20 samples analyzed with MALDI-ToF-MS but was not listed in any of the ingredients lists. ICP-QQQ-MS is a very sensitive technique and could both detect and verify the presence of all metal-containing pigments, as well as the level of impurities. Copper was clearly more present in green and blue colors, regardless of the brand. The metal content was evidently dependent on the brand for arsenic, aluminum, bismuth, chromium, nickel, zinc, and strontium. Elevated levels of barium and strontium (partially very high levels: up to 727 mg/kg barium and up to 8.06 g/kg strontium) were found in several samples. High amounts of aluminum (4 to 11,0 g/kg) and titanium (as judged from white precipitates and ingredients lists) were present in most samples. Nickel (0.1 to 41 mg/kg) and chromium (0.1 to 139 mg/kg) were also present in the samples. Some other impurities were also present (arsenic – 3.8 mg/kg, mercury – 1.6 mg/kg, and lead – 5.4 mg/kg for one sample, respectively). Known sensitizing pigments were declared and partially confirmed by MALDI-ToF-MS in 17 of 53 samples of the brands Radiant Colour, Eternal Ink, Fusion Tattoo Ink, and Kuro Sumi. Four samples (from Intenze, Eternal Ink, and Kuro Sumi) also declared pigments listed as non-suitable substance according to the European Commission regulation on cosmetic products from 2009.
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Löfstrand, Karin. "Trends and exposure of naturally produced brominated substances in Baltic biota - with focus on OH-PBDEs, MeO-PBDEs and PBDDs." Doctoral thesis, Stockholms universitet, Institutionen för material- och miljökemi (MMK), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-54421.
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The semi-enclosed and brackish Baltic Sea has become heavily polluted by nutrients, anthropogenic organic and inorganic chemicals via human activities. Persistent organic pollutants (POPs) have been thoroughly investigated due to their linkage to toxic effects observed in Baltic biota. There has been far less focus on semi-persistent pollutants e.g. naturally produced oraganohalogen compounds (NOCs) and their disturbances in the environment. This thesis is aimed on assessment of levels and trends of naturally produced brominated compounds in Baltic biota; more specifically on hydroxylated polybrominated diphenyl ethers (OH-PBDEs), methoxylated PBDEs (MeO-PBDEs) and polybrominated dibenzo-p-dioxins (PBDDs). These, NOCs, may originate from production in algae and cyanobacteria. OH-PBDEs and MeO-PBDEs may also be formed as metabolites of polybrominated diphenyl ethers (PBDEs), i.e. well-known commercial flame retardants. High levels of OH-PBDEs, MeO-PBDEs and PBDDs are shown within Baltic biota (cyanobacteria, algae, mussels, fish), often in much higher concentrations than PBDEs which are possible anthropogenic precursors of OH- and MeO-PBDEs. The levels of OH-PBDEs, MeO-PBDEs and PBDDs are higher in the Baltic Sea than on the west coast of Sweden. Temporal and seasonal variations show fluctuations in concentrations of OH-PBDEs, MeO-PBDEs and PBDDs, possibly related with macroalgal life-cycles. OH-PBDEs, MeO-PBDEs and PBDDs are present in several filamentous macroalgae species, but considering the levels quantified, the time of peak exposure and the species life-cycle the macroalgae, Pilayella, Ceramium and Cladophora are suggested as major natural producers of OH-PBDEs and PBDDs. The high levels of OH-PBDEs, MeO-PBDEs and PBDDs in the Baltic Sea may affect numerous organisms in the ecosystem. The toxic effects of OH-PBDEs and PBDDs are of particular concern. This thesis stress the importance of assessing and monitoring these substances, since the exposure to OH-PBDEs and PBDDs, during summer, may cause acute effects in Baltic fish and wildlife.<br>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: In press. Paper 4: Manuscript.
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Kjellberg, Viktor. "Evaluation of a UPLC-MS method using 18O-labelled water for the identification of hydrolytic degradants of drug substances." Thesis, Uppsala universitet, Avdelningen för analytisk farmaceutisk kemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-257712.
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In this master’s thesis the hydrolytic degradation in 18O-water solutions of six drug substances has been studied. The aim was to develop a mass spectrometric method for easier identification of degradants, since hydrolysis in 18O-water will generate degradants with higher mass compared with hydrolysis in regular water. The degradation was carried out in both acidic and basic conditions. About 10 % degradation was aimed for in the study and the storage time and conditions were adjusted to accommodate that. The samples were then analyzed with UPLC-MS. Separation was achieved on either an Acquity BEH C18 or HSS T3, 100 x 2.1 mm, 1.7 μm column. The mobile phases consisted of water and acetonitrile with the addition of 0.1 % formic acid. Structures for the detected degradants were proposed based on the molecular ion data from the regular and 18O-experiments. Most of these degradants have previously been reported. Structures for some previously unreported degradants are also proposed. These structures should need to be confirmed with future studies. The usefulness of the 18O-method has been evaluated and it was concluded that it is valuable to use as a complement to the generic hydrolytic experiment. In this study, the extra information gained from the 18O-experiment was used to confirm a number of proposed structures. It was also crucial in the rejection of two proposed structures for degradants of duloxetine. The method is most useful when confirming water involvement in reactions, for example in drug degradation. It is also a good alternative for obtaining structural information if the laboratory does not own a high-resolution MS.
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Fabregat, Safont David. "Application of advanced mass spectrometric techniques for the identification, metabolic characterisation and toxicological analysis of new psychoactive substances." Doctoral thesis, Universitat Jaume I, 2020. http://dx.doi.org/10.6035/14104.2020.419068.
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This Doctoral Thesis presents an in-depth investigation on NPS from the analytical chemistry point of view, being structured in three blocks. The first is focused on the analytical characterisation of different compounds, as well as the development of novel analytical strategies for their determination. The second includes the application of different in vitro and in vivo models for assessing the metabolism, potency and pharmacokinetics properties of different NPS. Finally, the third presents an investigation about the use of NPS among teenagers. All the information presented in this Doctoral Thesis will help forensic and toxicological laboratories working on NPS, providing useful information that includes analytical data for compound detection, novel instrumental methodologies, metabolic and pharmacokinetic information about the studied compounds, and showing the synthetic cannabinoids use among teenagers under control and/or treatment.<br>Esta Tesis Doctoral presenta una investigación en profundidad sobre las NPS desde el punto de vista de la química analítica, estructurándose en tres bloques. El primero se centra en la caracterización analítica de diversos compuestos, así como el desarrollo de nuevas estrategias analíticas para su determinación. El segundo incluye la aplicación de diferentes modelos in vitro e in vivo para evaluar el metabolismo, potencia y propiedades farmacocinéticas de diferentes NPS. Por último, el tercero presenta una investigación sobre el uso de la NPS entre los adolescentes. Toda la información presentada en esta Tesis Doctoral ayudará a los laboratorios forenses y toxicológicos que trabajan con NPS, proporcionando información útil que incluye datos analíticos para la detección de compuestos no reportados anteriormente, nuevas metodologías instrumentales, información metabólica y farmacocinética sobre los compuestos estudiados, y mostrando el uso de los cannabinoides sintéticos entre los adolescentes bajo control y/o tratamiento.<br>Programa de Doctorat en Ciències
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Ullberg, Malin. "Effects of pH and Cation Composition on Sorption of Per- and Polyfluoroalkyl Substances (PFASs) to Soil Particles." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-256415.
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Per- and polyfluoroalkyl substances (PFASs) have drawn great attention recently, due to their environmental persistence, potential toxicity and global distribution. PFAS is a large family of substances, characterized by a perflourinated carbon chain and a functional group. All PFASs are synthetic and have been widely used since the 1950s due to their unique properties of being both hydrophobic and oleophobic, making them useful for many industries. To be able to predict the fate of PFASs in the environment and to obtain detailed understanding of the transport processes, their partitioning behavior between soil particles and water depending on a range of parameters must be investigated. The aims of this study was to investigate the effects of pH, cation composition, functional group and perfluorocarbon chain length on sorption of PFASs to soil particles, by batch sorption experiment in laboratory scale. The laboratory-scale experiments were combined with modelling of the net charge to evaluate if net charge is a good predictor for sorption of PFASs to soil particles. 14 PFASs of varying length and functional groups were studied (PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFNA, PFDA, PFUnDA, PFDoDA, PFTeDA, PFBS, PFHxS, PFOS and FOSA). The effect on sorption of Na+, Ca2+ (two different concentrations) and Al3+ were investigated at pH-range 3-6. Modelling of net charge was carried out in the geochemical model Visual MINTEQ. The soil had 45% organic carbon content. The adsorption of PFASs was strongly correlated with perfluorocarbon chain length, showing a stronger adsorption to particles with increasing perfluorocarbon chain length (i.e. more hydrophobic). The relation between sorption (represented by the distribution coefficient log Kd) and perfluorocarbon chain length was linear for all PFSAs and C3 to C10 PFCAs. The PFSAs (sulfonate functional group) sorbed stronger to soil particles than the PFCAs (carboxylic functional group), and FOSA (sulfonamide functional group) sorbed the strongest. For most PFCAs, (C5-C13) there was a trend of decreasing log Kd (i.e. decreased sorption) with increasing pH, due to pH-dependent changes of the soil particle surfaces. For short and intermediate perfluorocarbon chain length PFCAs (C5-C8) and for PFHxS among the PFSAs, cations had a clear effect on sorption. Aluminium ions (trivalent, Al(NO3)3) had the largest effect, followed by calcium (divalent, Ca(NO3)2) where higher concentration resulted in stronger sorption. Sodium (univalent, NaNO3) had the least influence on sorption. The net charge modelled with Visual MINTEQ takes into account many parameters (including pH) that affect the surface charge and sorption of PFASs to soil particles. When comparing log Kd for the different PFASs with pH and net negative charge, net charge was a better predictor of sorption of PFASs to soil particles than solution pH alone.<br>Per- och polyfluoroalkylsubstanser (PFAS:er) har dragit stor uppmärksamhet till sig på senare tid, på grund av deras persistenta egenskaper, potentiella toxicitet och globala utbredning. PFAS är en stor grupp ämnen, kännetecknad av en perflourinerad kolkedja och en funktionell grupp. Alla PFAS är syntetiska och har använts i stor utsträckning sedan 1950-talet på grund av deras unika egenskaper av att vara både vatten- och fettavstötande, vilket gör dem användbara för många industriella tillämpningar. För att kunna förutsäga var dessa föroreningars hamnar i miljön och få mer detaljerad förstående för transportprocesserna, måste deras fördelningbeteende mellan jordpartiklar och vattenundersökas för en rad olika parametrar. Syftet med denna studie var att undersöka effekterna av förändrat pH, katjonsammansättning, funktionell grupp och perfluorkolkedjelängd på sorption av PFAS:er till jordpartiklar. Detta gjordes med sorptionsexperiment i laboratorieskala. Laboratorieexperimentet kompletterades med modellering av nettoladdning, för att se huruvida detta väl kunde förklara sorptionen till jordpartiklar. 14 PFAS:er av varierande längd och med tre olika funktionella grupper studerades (PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFNA, PFDA, PFUnDA, PFDoDA, PFTeDA, PFBS, PFHxS, PFOS och FOSA). Effekten på sorption av Na+, Ca2+ (två olika koncentrationer) och Al3+ undersöktes vid pH-intervallet 3-6. Modellering av nettoladdning utfördes i den geokemiska modellen Visual MINTEQ. Jorden som användes hade en halt av organiskt kol på 45%. Adsorptionen av PFAS:er var starkt positivt korrelerad med kedjelängden på de perfluorinerade kolkedjan. Ju längre kolkedja (dvs. mer hydrofob), desto starkare adsorption till partiklar. Relationen mellan sorptionen (här uttryckt som partitioneringskofficienten log Kd) och kedjelängd var linjär för alla PFSA och för C3 till C10 för PFCA. PFSA (sulfonat) adsorberade starkare än PFCA (karboxyl), och FOSA (sulfonamid) adsorberades starkast. För de flesta PFCA, (C5-C13) fanns en allmän trend där log Kd (dvs. sorption) minskade med ökande pH, på grund av pH-beroende förändringar på jordpartiklarna. För korta och medellånga PFCA (C5-C8) och för PFHxS hade katjonsammansättningen en tydlig effekt på sorptionen. Aluminiumjoner (trevärd, Al(NO3)3) hade den största effekten, följt av kalcium (tvåvärd, Ca(NO3)2) där den högre koncentrationen resulterade i starkare sorption. Natrium (envärd, NaNO3) hade minst påverkan på sorptionen till jordpartiklar. Visual MINTEQ tar hänsyn till många parametrar (inklusive pH), när nettoladdningen på jordpartiklarnas yta räknas ut. När log Kd för olika PFAS:er jämfördes med endera pH eller negativ nettoladdning, drogs slutsatsen att nettoladdning korrelerade bättre med sorption än pH.
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Koriko, Moursalou. "Extraction, caractérisation, réactivité chimique des substances humiques naturelles avec les phosphates de Hahotoe-Kpogame et leurs propriétés photodégradantes." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2010. http://tel.archives-ouvertes.fr/tel-00719333.
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Les recherches de rendements agricoles de plus en plus élevés conduisent à l'utilisation des engrais chimiques et des produits phytosanitaires. L'utilisation non raisonnée de ces intrants agricoles a pour conséquences la pollution des sols, des eaux de surface et des eaux souterraines. Les recherches sur l'élaboration de nouveaux types de fertilisants écologiques et le devenir des polluants organiques dans l'environnement s'avèrent importantes. C'est dans ce cadre que se situe notre travail. La première étape de ce travail a été l'extraction et la caractérisation des substances humiques naturelles. Celles-ci ont été extraites d'un sol de Lomé (AHSL, AFSL), d'un sol de Badou (AHSB, AFSB) et d'un compost (AHC, AFC) élaboré à partir de déchets biodégradables. Les caractérisations de ces substances d'une part par analyse élémentaire et dosage du carbone organique total et d'autre part, par des méthodes physico-chimiques (ultraviolet-visible, Microscopie Electronique à Balayage, Infra Rouge) ont prouvé les caractères organique et humique de ces échantillons. Dans la deuxième partie, la dissolution des phosphates naturels de Hahotoé - Kpogamé (Togo) par des acides conventionnels (minéraux et organiques) et des substances humiques naturelles a été réalisée. Les résultats obtenus ont permis de montrer que : - la dissolution de l'apatite en milieu fortement acide est due essentiellement à l'attaque des ions hydronium. C'est d'ailleurs le seul effet de dissolution des acides minéraux; - la dissolution du minerai en milieux faiblement acide et alcalin par les solutions organiques est due à la complexation des ions métalliques (Ca2+) par les groupements fonctionnels. Le mécanisme des cette dissolution a été mis en évidence par des dosages conductimétriques et potentiométriques. Le pouvoir complexant de ces solutions augmente avec le pH. Ce mécanisme de complexation des substances humiques vis-à-vis des ions métalliques en général et du calcium en particulier peut donc être utilisé pour l'élaboration de nouveaux types d'engrais à base de la matière organique biodégradable et du phosphate naturel. Parallèlement aux études de dissolution, la dernière partie de notre travail a consisté à évaluer les capacités des substances humiques à photodégrader les polluants organiques. Les résultats obtenus montrent clairement que les acides humiques utilisés sont des inducteurs efficaces qui permettent la photodégradation de polluants organiques sous excitation solaire. Cette photodégradation est due à la formation par la matière organique des espèces réactives telles que l'oxygène singulet, les radicaux hydroxyles et les états excités à caractère triplet. En application de ces résultats, une étude de la photodégradation du profenofos (O(4-bromo-2- chlorophényl), O-éthyl, S-propylphosphorothioate) qui est un polluant organochloré utilisé dans la culture cotonnière au Togo par ces substances humiques a été réalisée. Les résultats montrent effectivement la transformation du polluant. Cette transformation est ralentie en milieu désoxygéné et en présence du propan-2-ol qui piège les radicaux hydroxyle issus des substances humiques. Ceci montre que ces radicaux sont à la base de la photodégradation du polluant organique. L'identification des intermédiaires dans les conditions diverses nous a conduit à proposer des structures des produits issus de la phototransformation.
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Kazi, Haseeb. "Plasma Interactions on Organosilicate Glass Dielectric Films and Emerging Amorphous Materials- Approach to Pore Sealing and Chemical Modifications." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc801876/.
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In-situ x-ray photoemission (XPS) and ex-situ FTIR studies of nanoporous organosilicate glass (OSG) films point to the separate roles of radicals vs. VUV photons in the carbon abstraction. The studies indicate that reaction with O2 in presence of VUV photons (~123 nm) result in significant carbon abstraction within the bulk and that the kinetics of this process is diffusion-limited. In contrast, OSG exposed to atomic O (no VUV) results in Si-C bond scission and Si-O bond formation, but this process is self-limiting after formation of ~1 nm thick SiO2 surface layer that inhibits further diffusion. Therefore, the diffusion-dominated kinetics of carbon abstraction observed for OSG exposed to O2 plasma is definitively attributed to the diffusion of O2 down OSG nanopores, reacting at photo-activated sites, rather than to the diffusion of atomic O. Pretreatment of OSG by 900 eV Ar+ ion bombardment also results in formation of 1 nm thick SiO2-like surface overlayer that inhibits O2 diffusion, inhibiting VUV+O2 and O2 plasma-induced reactions, and that the effectiveness of this treatment increases with ion kinetic energy. On the contrary, organosilicate glass (OSG) films with backbone carbon (-Si-R-Si-) exhibit significantly enhanced resistance to carbon loss upon exposure to O2 plasma, radicals and VUV+O2 compared to films with terminal methyl groups (Si-CH3). Films incorporating backbone carbon chains (-Si-R-Si-) were deposited from 1,2 bis (triethoxysilyl) ethane (BTESE) precursor by ebeam or plasma cross-linking. The radical effects on BTESE film indicates negligible carbon loss or Si oxidation, combined with C-O bond formation, under conditions where OSG films with terminal methyl groups exhibit > 80% carbon loss within the surface region of the film. C-O bond formation is never observed for terminal CH3 groups. Further, backbone carbon (-Si-R-Si-) films exposed to VUV+O2 exhibit self-limiting, minimal net carbon loss. This indicates that plasma-induced Si-C bond rupture still occurs in the linking unit, but with a low probability of simultaneous rupture of both Si-C bonds required for abstraction of an in-line methylene bridging group. The data thus demonstrate that OSG films containing backbone carbon groups exhibit greatly reduced rates of carbon loss in the presence of O2 plasma, radicals or VUV+O2 compared to films with terminal carbon groups due to fundamentally different patterns of Si-C bond scission. The results demonstrate the potential of backbone carbon low-k films to resist plasma induced damage.
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Ahamada, Kadiria. "Stratégies biomimétiques en vue de la synthèse totale de deux substances naturelles polycycliques complexes : la bipléiophylline et l'haliclonine A." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA114807/document.
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Les travaux présentés concernent dans une première partie la synthèse biomimétique d’un alcaloïde indolomonoterpénique : la bipléiophylline. La bipléiophylline est le résultat de l’assemblage complexe de deux unités indoliques identiques ancrées sur une plateforme aromatique. Une stratégie générale de synthèse biomimétique de la bipléiophylline consistant i) à la synthèse de l’unité indolique pléiocarpamine et ii) à l’oxydation de l’acide 2,3-dihydroxybenzoïque a été envisagée. L’accès au squelette complexe de la pléiocarpamine a été étudié selon plusieurs stratégies de synthèse totale mais également par hémisynthèse. Parallèlement une étude des conditions d’oxydation notamment par électrochimie de l’acide 2,3-dihydroxybenzoïque ont permis de déterminer et caractériser son potentiel d’oxydation et de mettre au point les conditions de formation de sa forme oxydée. La seconde partie est consacrée à la synthèse biomimétique d’un modèle du cœur central de l’haliclonine A, un alcaloïde de la famille des manzamines. La synthèse de plusieurs précurseurs a été réalisée ainsi que l’étude de l’étape clé de double addition nucléophile sur un 5,6-dihydropyridinium<br>Our work deals in the first part with a biomimetic synthesis of bipleiophyllin, an indolomonoterpenic alkaloid. The bipleiophyllin is the result of a complex anchorage of two identical indolic subunits on an aromatic platform. A general strategy for the biomimetic synthesis of bipleiophyllin consisting of i) the synthesis of the indolic unit pleiocarpamin and ii) the oxidation of 2,3-dihydroxybenzoic acid; was considered. Access to the complex skeleton of pleiocarpamin has been studied by different total synthesis strategies but also by hemisynthesis. Meanwhile this work, a study of the oxidation conditions of 2,3-dihydroxybenzoic acid including by electrochemistry, helped identify and characterize its oxidation potential and develop the required conditions to obtain its oxidized form. The second part is devoted to the biomimetic synthesis of a model compound, mimic of the central core of haliclonin A, an alkaloid of the family of manzamins. The synthesis of several precursors and the study of the key step consisting in a double nucleophilic addition to a 5,6-dihydropyridinium were done
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Yan, Lok-Hang. "Approche biomimétique des manadomanzamines et préparation d’analogues de la pelletiérine pour la synthèse biomimétique d’alcaloïdes de lycopodes." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA114812/document.
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Au cours de ce travail, nous nous sommes intéressés dans une première partie à la synthèse biomimétique d’alcaloïdes de type manzamines et plus particulièrement, aux manadomanzamines. Une étude de la réactivité des deux intermédiaires clés de leur biogenèse, les glutaconaldéhydes et les aminopentadiènals, a été entreprise. Ces mêmes molécules ont ensuite été utilisées comme équivalents synthétiques dans une synthèse biomimétique du squelette pentacyclique de la manadomanzamine A. Une seconde partie est consacrée à la préparation d’analogues stables de la pelletiérine en vue d’une synthèse biomimétique d’alcaloïdes du genre Lycopodium<br>This work is dedicated to the biomimetic synthesis of complex polycyclic alkaloids namely the manzamine alkaloids and especially to manadomanzamine. The biogenetic hypotheses postulated for these alkaloids are reported in a first introductory chapter. A few examples of manzamine alkaloids biogenesis are described and compared. The second chapter is focused on the reactivity of reactive units (considered as simplified models of two key biosynthetic intermediates, namely glutaconaldehydes and aminopentadienals) resulting from the ring-opening of pyridinium salts, and their implication in natural products synthesis. Particularly detailed are the investigations conducted on 5-dimethylamino-2-methylpenta-2,4-dienal and the condensation of potassium glutaconaldehyde onto a pyridinium salt. The chemistry of these reactive units has been exploited to design several model studies towards the synthesis of pentacyclic indole nucleus of manadomanzamine A, isolated from an Indonesian sponge Acanthostrongylophora sp.. These biomimetic models, elaborated from a biosynthetic intermediate postulated in our biosynthesis hypothesis have culminated in the synthesis of the central pentacyclic indole nucleus. The last chapter reports the preparation of more or less oxidized analogs of pelletierine, the well known alkaloid isolated from Punica granatum. Compounds such as phenyloxazolopelletierine have been prepared and their reactivity investigated in view of the biomimetic synthesis of Lycopodium alkaloids