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1
Asres, Daniel Derbie. "Characterization of carbohydrates using gas chromatography/mass spectrometry (GC/MS)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0001/MQ41677.pdf.
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Lu, Yao. "Forensic Applications of Gas Chromatography-Differential Mobility Spectrometry, Gas Chromatography/Mass Spectrometry, and Ion Mobility Spectrometry with Chemometric Analysis." Ohio University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1267816777.
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De, Vos Betty-Jayne. "Gas chromatography coupled with ion trap mass spectrometry (GC-MS and GC-MS-MS) - for arson debris analysis." Diss., Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-02082006-160506.
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Milo, John A. "Quantitation of Halogenated Anisoles in Wine via SPME – GC/MS." Connect to resource online, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1230924488.
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Skinner, Michael A. "Hapsite® gas chromatograph-mass spectrometer (GC/MS) variability assessment /." Download the thesis in PDF, 2005. http://www.lrc.usuhs.mil/dissertations/pdf/Skinner2005.pdf.
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Zhai, Lailiang. "Gas Chromatography: Mass Spectrometry of Chemical Agents and Related Interferents." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1266.pdf.
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Christison, Krege Matthew. "Exploring the Molecular Origin of Jet Fuel Thermal Oxidative Deposition Through Statistical Analysis of Mass Spectral Data and Pyrolysis Gas Chromatography/Mass Spectrometry of Deposits." Scholarly Commons, 2019. https://scholarlycommons.pacific.edu/uop_etds/3639.
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ASTM D3241 (Standard Test Method for Thermal Oxidation Stability of Aviation Turbine Fuels) measures the thermal oxidative stability of jet fuels under elevated temperature and pressure conditions. When jet fuels fail ASTM D3241, either at the refinery or in the distribution system, there can be supply disruptions and financial losses. Understanding the causes of poor thermal oxidative stability in jet fuels could help prevent or mitigate issues. In order to develop a deeper understanding of the molecular precursors that lead to ASTM D3241 failures, a number of analytical methodologies and data treatment techniques have been developed, applied, and reported here. Statistical analysis of LC/MS ESI data from jet fuels with varying thermal oxidative stabilities allows for the identification of molecules that are significant to ASTM D3241 failures. Differential statistical analysis of LC/MS ESI data from jet fuels before and after thermal oxidative stressing in a QCM reactor elucidates which significant molecules are being consumed during oxidation and which molecules are increasing in abundance. The analysis of thermal oxidative deposits that form during thermal oxidative stressing in the QCM reactor allows for the insight into the molecular components of the deposits. Attapulgus clay removes the polar molecules that lead to thermal oxidative stability issues in the refinery. Extraction of Attapulgus clay that has been used in a refinery to filter jet fuel with a series of solvents removes the polar molecules into a series of fractions. The subsequent analysis of the fractions by comprehensive GCxGC/MS leads to the identification of the different homologous series of molecules that are removed by the clay.
The analyses developed and employed here are shown to be particularly useful for the analysis of trace polar nitrogen and oxygen containing molecules. Similar homologous series of molecules are identified across all of the different analyses. It is also clear from some of the analyses, along with previously reported data in the literature, that reactive sulfur-containing molecules are significant to poor thermal oxidative stability as measured by ASTM D3241 and to the formation of thermal oxidative deposits. There is still an opportunity to find methodologies to better characterize the sulfur species present and correlate them to the data that is reported here.
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Li, Xifeng. "Removal of warmed-over flavor using absorbent and pattern recognition analysis of overall flavors by SPME-GC/MS-MVA /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p1426082.
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Nezami, Ranjbar Mohammad Rasoul. "Novel Preprocessing and Normalization Methods for Analysis of GC/LC-MS Data." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/73499.
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We introduce new methods for preprocessing and normalization of data acquired by gas/liquid chromatography coupled with mass spectrometry (GC/LC-MS). Normalization is desired prior to subsequent statistical analysis to adjust variabilities in ion intensities that are not caused by biological differences. There are different sources of experimental bias including variabilities in sample collection, sample storage, poor experimental design, noise, etc. Also, instrument variability in experiments involving a large number of runs leads to a significant drift in intensity measurements. We propose new normalization methods based on bootstrapping, Gaussian process regression, non-negative matrix factorization (NMF), and Bayesian hierarchical models. These methods model the bias by borrowing information across runs and features. Another novel aspect is utilizing scan-level data to improve the accuracy of quantification. We evaluated the performance of our method using simulated and experimental data. In comparison with several existing methods, the proposed methods yielded significant improvement. Gas chromatography coupled with mass spectrometry (GC-MS) is one of the technologies widely used for qualitative and quantitative analysis of small molecules. In particular, GC coupled to single quadrupole MS can be utilized for targeted analysis by selected ion monitoring (SIM). However, to our knowledge, there are no software tools specifically designed for analysis of GS-SIM-MS data. We introduce SIMAT, a new R package for quantitative analysis of the levels of targeted analytes. SIMAT provides guidance in choosing fragments for a list of targets. This is accomplished through an optimization algorithm that has the capability to select the most appropriate fragments from overlapping peaks based on a pre-specified library of background analytes. The tool also allows visualization of the total ion chromatogram (TIC) of runs and extracted ion chromatogram (EIC) of analytes of interest. Moreover, retention index (RI) calibration can be performed and raw GC-SIM-MS data can be imported in netCDF or NIST mass spectral library (MSL) formats. We evaluated the performance of SIMAT using several experimental data sets. Our results demonstrate that SIMAT performs better than AMDIS and MetaboliteDetector in terms of finding the correct targets in the acquired GC-SIM-MS data and estimating their relative levels.Ph. D.
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Ofori, Hayford. "Characterisation of sandalwood essential oils using high performance thin-layer chromatography and high resolution gas chromatography mass spectrometry." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2020. https://ro.ecu.edu.au/theses/2326.
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Sandalwood essential oil is extensively used in perfumes, cosmetics, and pharmaceuticals. The unique woody aroma of sandalwood essential oil is produced by (Z)-α-santalol and (Z)-β-santalol and these two compounds influence the oil quality. Variation in sesquiterpene composition and oil yield have been observed both within and across Santalum species. Gas Chromatography-Mass Spectrometry (GC-MS) is a technique commonly used to identify and quantify sesquiterpene compounds in sandalwood essential oils. High Performance Thin-Layer Chromatography (HPTLC) has yet to be fully explored as an alternative to GC-MS in authenticating sandalwood essential oils of different species. In this study, sandalwood essential oils were characterised using HPTLC and high resolution GC-MS.
The potential of HPTLC to identify differences in sandalwood essential oils of Santalum album, Santalum spicatum, Santalum austrocaledonicum, Santalum paniculatum, Santalum lanceolatum and a natural substitute for sandalwood, Osyris lanceolata, was explored. Variation was observed in the profile of bands and peak intensity profiles of the essential oils with some bands being unique to the individual species. The potential of HPTLC fingerprinting as a quality control tool in identifying differences in sandalwood essential oils was demonstrated (Study I).
Study I was limited to a maximum of five oils for each species studied. The natural variability was likely not captured for such a small sample size. The potential of HPTLC to generate a sandalwood profile that better represents Santalum album, Santalum spicatum, Santalum austrocaledonicum and Santalum paniculatum was explored. Santalum spicatum could confidently be distinguished from other species with a distinctive pink band at RF 0.71 and unique peak intensities at RF 0.28, 0.45 and 0.47. Santalum album and Santalum paniculatum could easily be distinguished from each other with distinctive peak intensities at RF 0.51 and 0.17 respectively. The intense peak at RF 0.09 displayed by Santalum austrocaledonicum distinguished it from Santalum album, and Santalum paniculatum but not Santalum spicatum (Study II).
An ultrasonication extraction method was optimised for extraction of essential oil from Western Australia sandalwood (Santalum spicatum) using n-hexane, isopropanol, and n-hexane/isopropanol (50:50, v/v) for different extraction times. Oil yield was moderately influenced by solvent, particle size and extraction time. Extracting for 30 minutes with particle size 250µm-500µm using n-hexane gave the highest oil yield and santalol content. The santalol content achieved in Santalum spicatum extract was influenced by particle size and solvent (Study III).
The optimised method in Study III was moderately modified and successively applied to extract oil from 340 milled heartwoods of Santalum spicatum. GC-MS analysis was performed on oil extracts. Variation in sesquiterpene composition of 340 heartwood oil extracts of Santalum spicatum sampled from 19 locations across five regions in Western Australia was explored. Variation was observed in sesquiterpene composition, and oil yield both across and within all five regions. Heartwood oil extracts from trees in the north obtained higher oil yield and santalol content when compared to oil extracts from trees in the south. Interestingly, one oil extract of S. spicatum met the ISO specification of 90% combined α-santalol and β-santalol in Santalum album, obtaining 67.47% α-santalol and 22.92% β-santalol (Study IV).
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Kato, Dawn M. "APPLICATIONS OF GAS CHROMATOGRAPHY/MASS SPECTROMETRY AND CAPILLARY ELECTROPHORESIS FOR THE ANALYSIS OF LIGNOCELLULOSIC BIOMASS PRETREATMENT." UKnowledge, 2014. http://uknowledge.uky.edu/chemistry_etds/45.
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The focus of this dissertation centers on the development and applications of gas chromatography/mass spectrometry and capillary electrophoresis methodologies to quantify monomeric compositions of the β-O-4 linkages in lignin. Pretreatment is a required step in the utilization of lignocellulosic biomass for biofuels. Lignin is the target of pretreatment because it hinders the accessibility of enzymes and chemicals to cellulose. The effects of pretreatment are commonly assessed utilizing enzymatic saccharification and lignin assays. However, these techniques do not elucidate the effects of pretreatment on the monomeric make up of lignin.
The overarching hypothesis of this dissertation is that changes in individual monolignol content upon pretreatment can be observed from quantification. To test the hypothesis, a pretreatment, solution phase Fenton chemistry, was conducted on various lignocellulosic biomass feedstocks. Enzymatic saccharification studies showed a significant increase in glucose production upon Fenton pretreatment, however, lignin assays did not show a significant decrease in lignin content.
Project two of this dissertation aimed to synthesize analytical standards in order to develop a quantitative thioacidolysis technique. The successful synthesis of the three arylglycerols were conducted utilizing and epoxidation reaction scheme which was hypothesized to produce a single diastereomer, as supported by GC/MS and chiral CE analysis. Upon method development, a quantitative thioacidolysis GC/MS method was applied to untreated and Fenton treated biomass. Results from this project revealed there was no significant change in the three lignin monomers. To verify the method, quantitative thioacidolysis GC/MS method was applied to a pretreatment method known to degrade lignin, alkaline peroxide pretreatment. The results of this project showed a significant change in monolignol concentrations upon alkaline peroxide pretreatment.
Analytical degradative techniques, such as thioacidolysis, has traditionally assessed lignin as monomeric ratios. However, as this dissertation showed, upon alkaline peroxide pretreatment, no significant change was seen in the monomeric ratios, but there was a significant difference in all three monolignol concentrations. These results support the overall hypothesis that changes in individual monolignol content upon pretreatment can be observed from quantification. The works of this dissertation provides an analytical method which contributes to the elucidation of lignin.
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Wang, Ting. "Monitoring a natural autoxidation process of methyl linoleate by using GC-MS." Scholarly Commons, 2003. https://scholarlycommons.pacific.edu/uop_etds/586.
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The methyl ester of an unsaturated fatty acid, methyllinoleate was reacted with oxygen in a pressurized system at a controlled temperature. A natural autoxidation of methyl linoleate was observed without the addition of an initiating reagent. This autoxidation process could be used to mimic the course of lipid peroxidation, which is the major cause ofradical damage to living cells. The technology of GC-MS was employed to monitor the autoxidation of methyllinoleate.
Eight of the autoxidation products separated by GC column were identified by interpreting the corresponding EI ion mass spectra. The products from 9-alkoxy methyl linoleate radical were methyl octanate, 2,4-decadienal, nonanoic acid, 9-oxo-methyl ester, and its further oxidation product, nonanedioic acid, monomethyl ester. All of them formed through a pathway of beta-cleavage. The products from 13-alkoxy methyl linoleate radical were tridecanoic acid, 9, 11-diene-13-oxo-methyl ester, hex anal, and its further oxidation product, hexanoic acid. They were also formed through a mechanism of beta-cleavage. The fourth product from 13-alkoxy methyllinoleate radical was 13-keto-9, 11-octadecadienoic acid, methyl ester, which was obtained through a pathway of keto formation. Observation of their concentrations in the samples at different autoxidation periods revealed the time-course of formation of these products.
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Manzoor, K. "Detection and analysis of spin trapped radical adducts using thermal desorption gas chromatography mass spectrometry (TD-GC-MS)." Thesis, University of Salford, 2018. http://usir.salford.ac.uk/48345/.
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Certain oxygen free radicals are produced constantly in cells by metabolism and exogenous agents. Some, such as the hydroxyl radical, may react with various biomolecules like DNA, lipids or proteins, and thus be involved in the pathogenesis of various diseases. It is often difficult to detect oxygen free radicals due to their relatively short half-life. This problem may be overcome, however, using the spin trapping technique. In this technique, the spin-trap compound is used to trap free radicals, making them stable enough to be analysed using techniques like Electron Paramagnetic Resonance (EPR) spectroscopy or Mass Spectrometry (MS). In the current study, Fenton chemistry has been used to generate hydroxyl radicals. Since the hydroxyl radical adduct of the spin-trap N-tert-butyl-α-phenylnitrone (PBN) is shortlived at room temperature a secondary trapping technique is employed. The resulting spin-trapped species have been sampled using solvent-free extraction approaches i.e. Headspace Solid Phase Microextraction (HS-SPME) or Thermal desorption (TD), and the extracted products then detected and identified by using gas chromatography-mass spectrometry (GC-MS). GC-MS provides an alternative to other traditional techniques like EPR spectroscopy, as it provides more detailed information about structure of the radical adduct. Aldehydes are some of the most important products of oxidative stress, mostly produced through lipid peroxidation, and potentially may be used as biomarkers for different diseases. Their reactivity, production in low quantities and need of derivatisation are some of the challenges faced by analytical chemists to detect them. In the current research, aldehydes are used as secondary source of radicals in the Fenton reaction to produce aldehyde related free radicals. The developed method is not only a solvent free approach but also there is no need of derivatisation. It has the potential to be used as a biomarker assay of oxidative stress.
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Miranda, e. Silva Lígia Maria 1982. "Validação de método de análise de multiresíduos de defensivos agrícolas por GC-MS/MS e LC-MS/MS." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/254815.
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Orientador: Marcelo Alexandre PradoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: O crescente aumento populacional em escala mundial, tornou necessário um grande esforço por parte da agricultura para aumentar, a cada ano, a produção de alimentos para atender as necessidades do mercado externo e interno do Brasil. Recursos técnicos e científicos passaram então, a serem aplicados em busca da melhoria na produção dos cultivos,principalmente mediante o uso de fertilizantes e praguicidas. Com isso, a sociedade se deparou com problemas de ordem de equilíbrio ambiental e saúde pública, pois devido à contínua diversificação dos fitoparasitas, surgem, a todo momento, reduções do período de tempo entre aplicações consecutivas, e mais importante talvez, usos de doses mais altas e emprego simultâneo de diferentes pesticidas, por parte dos agricultores, objetivando complementar ações específicas ou alcançar efeitos sinérgicos para maiores rendimentos na produção. Tal situação traz como conseqüência óbvia e direta, o aumento, inaceitável, dos riscos de contaminação do meio ambiente com resíduos químicos de defensívos da área agropecuarista prejudiciais à saúde, o que leva a inúmeros problemas relativos à segurança alimentar dos produtos consumidos, e à uma preocupação de âmbito nacional evidenciada pela criação do Programa de Análise de Resíduos de Agrotóxicos em alimentos (PARA) da ANVISA. O aumento na necessidade de detecção e quantificação destes compostos, acarretou o desenvolvimento de pesquisas no setor, a fim de atingir uma melhoria na eficiência,qualidade e rapidez de resposta nas análises. A possibilidade do estudo de não apenas um de cada vez, mas de até 300 compostos sendo extraídos, detectados e quantificados simultâneamente se tornou a saída mais viável, tanto qualitativa quanto economicamente, facilitando o monitoramento contínuo do fornecimento de produtos do setor alimentício pelos chamados métodos multiresíduos. O presentre trabalho teve como princípio a validação de um método multiresíduo para análise de 14 analitos usando uma técnica de alto poder de concentração e limpeza do extrato como o GPC (Gel Permeation Chromatography) e detecção e quantificação por GC-MS/MS e LC-MS/MS. Os pesticidas investigados englobam classes como: acaricidas, inseticidas, fungicidas, nematicidas e formicidas de aplicação foliar, em sementes ou em solo, sendo que o acefato, metamidofós, acetamiprido e o thiamethoxan foram extraídos de amostras de batata e feijão e analisados por LC-MS/MS e a azoxistrobina, bifentrina, carbofuran, chlorotalonil, clorpirifós, clorfenapir, etofenprox, famoxadone,metalaxil, procimidone e o tebuconazole em amostras de batata e tomate e analisados por GCMS/MS. Os limites de detecção (LD) encontrados variaram de 0,06 a 2,89µg/L, e os coeficientes de variação (CV), de 0,036 a 2,036%. As recuperações foram determinadas em cada tipo de amostras, e os valores encontrados estavam entre 93,34% e 109,67%. Nenhuma das matrizes utilizadas apresentaram resultados insatisfatórios e o método utilizado mostrouse robusto e de fácil aplicação para todos os analitos testados
Abstract: The growing population worldwide, has required a great effort on the part of agriculture to increase each year, the production of food to meet the needs of external and internal market of Brazil. Technical and scientific resources spent then, to be applied in pursuit of improved crop production, mainly through the use of fertilizers and pesticides.With this, the company encountered problems in the balance of environmental and public health, since due to the continuous diversification of plant parasites, arise at any moment,reductions in the time period between consecutive applications, and perhaps most important,uses more doses high and simultaneous use of different pesticides by farmers, aiming to complete specific actions or to achieve synergistic effects in producing higher yields. This situation brings obvious and direct consequence, the increase unacceptable risk of environmental contamination with chemical residues from pesticides in farms are harmful to health, which leads to numerous problems relating to food safety of the products consumed, and to a concern nationwide evidenced by the creation of the Program Analysis of Pesticide Residues in Food (TO) of ANVISA. The increase in the necessity for detection and quantification of these compounds, led the development of research in the sector in order to achieve an improvement in efficiency, quality and responsiveness in the analyzes. The possibility of studying not just one at a time, but up to 300 compounds being extracted,detected and quantified simultaneously output became more viable, both qualitatively and economically, facilitating continuous monitoring of the supply of products by the food industry called methods multiresidue. The principle presentre work was the validation of a multiresidue method for analysis of 14 analytes using a technique of high power concentration and cleanup of the extract as GPC (Gel Permeation Chromatography) and detection and quantification by GC-MS/MS and LC- MS / MS. The pesticides investigated include classes such as acaricides, insecticides, fungicides, insecticides and nematicides foliar, seed or soil,and acephate, methamidophos, and Acetamiprid thiamethoxan were extracted from samples of potatoes and beans and analyzed by LC-MS / MS and azoxystrobin, bifenthrin, carbofuran,chlorothalonil, chlorpyrifos, chlorfenapyr, etofenprox, famoxadone, metalaxyl, procymidone and tebuconazole in samples of potato and tomato and analyzed by GC-MS/MS. The limits of detection (LOD) ranged from 0.06 to 2.89 mg / L, and the coefficients of variation (CV), 0.036 to 2.036%. The recoveries were determined for each type of samples, and the values were between 93.34% and 109.67%. None of the arrays used had unsatisfactory results and method proved to be robust and easy to apply for all analytes tested
Mestrado
Ciência de Alimentos
Mestra em Ciência de Alimentos
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Kamalia, Uswatun Hasanah Isna. "Identification of Sources for Illegal Oil Spills by Using GC-MS (Gas Chromatography and Mass-Spectrometry) Databases and Multivariate Statistics." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for kjemi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-14830.
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Preparing a defensible oil spill fingerprinting is always challenging. Presently available well established method for this purpose is a univariate method by comparison of diagnostic ratio using repeatability limit as suggested by European Committee for Standardization (CEN)-method. The consistency result of this method, however, tends to depend on the skill of the analyst who performs the analysis. The shortcoming of CEN-method was then demonstrated by the application of the method to the "MS Server" and "MV Full City" oil spill cases. The author’s analysis result exposed some discrepancieswhen was compared with the one performed by SINTEF. Therefore, this thesis focuses on the effort of pursuing alternative or at least complimentary methods to ease the shortcoming of the CEN-method. The main investigation was then emphasized on the possibility of employing the multivariate analyses, i.e. principal component analysis (PCA), cluster analysis, and partial least square discriminant analysis (PLS-DA). The performance of those multivariate analyses were examined by applying to the case studies of "MS Server" and "MV Full City" oil spills. Later on, it was found that PCA failed to classify the samples properly according to the match or non-match with the reference samples. The power of the PCA was revealed when the method was combined with thecluster analysis. The PCA combined with the cluster analysis demonstrated to be faster and undoubtedly more objective (in term of the analyst skill and expertise) as compared to the CEN-method. PLS-DA also showed the same benefits. Moreover, the PLS-DA gives more similar result to the CEN-method applied by SINTEF (irrespective of the difference gaps of the analysts skill, i.e. the SINTEF researchers v.s. the author) as compared to the PCA combined with the cluster analysis. However, the main drawback of the PLS-DA is therequirement of quite large number of sample to obtain a good result. At last, we could see that there is possibility of applying several multivariate analyses, i.e PCA combined with the cluster analysis, and PLS-DA, for the alternatives or complementary of a well established univariate analysis of oil spill fingerprinting (CEN-method). In order to develop the alternative method(s) properly, further research is needed, especially the one which employs more controllable samples.
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Jaeger, Frederick Howard. "Simplified Plant Sample Preparation for use in Gas Chromatography-Mass Spectrometry (GC-MS) Based Metabolomic Profiling and Targeted Analyte Quantitation." NCSU, 2008. http://www.lib.ncsu.edu/theses/available/etd-02202008-155316/.
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A simple, fast, reproducible and less laborious sample preparation protocol was developed for the analysis of Arabidopsis thaliana using Gas chromatography coupled with mass spectrometry (GC-MS). In particular, a semi-automated machine tool is used to replace the traditional mortar-pestle method in tissue grinding. One-pot chemical extraction-derivatization is used to provide simplified sample preparation over the conventional multi-step liquid-liquid extraction protocol. Wild-type and transgenic Arabidopsis thaliana seedlings were used as the model system to evaluate performance of this newly developed method for use in metabolic profiling and also targeted quantitative analysis of salicylic acid for the study of systemic acquired resistance.
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Sýkora, Richard. "Využití GC/MS při analýze léčiv." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2011. http://www.nusl.cz/ntk/nusl-216709.
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This diploma thesis is based on the current issue of the presence of pharmaceuticals in various components of the environment. Concerning the contamination by residues of pharmaceuticals the most affected environment is the aquatic environment where these substances leaks especially from wastewater treatment plants, which eliminate them during the cleaning process only partially. This work is focused on the selected group of pharmaceuticals, non-steroidal anti-inflammatory drugs (salicylic acid, ibuprofen, caffeine, naproxen, ketoprofen, diclofenac) in waste water. For analysis purposes two types of sampling were used and compared: the conventional spot sampling of wastewater and the sampling using passive samplers POCIS. The sampling took place at the inflow and outflow of the wastewater treatment plant in Brno Modřice. The solid phase extraction (SPE) using Oasis HLB columns was used as the extraction method. Extracted sample was derivatized then. Derivatization agents were: MSTFA (N-methyl-N-(trimethylsilyl)trifluoroacetamid) and BSTFA (N, O-bis(trimethylsilyl) trifluoroacetamid). The final analysis was performed using gas chromatography with mass spectrometric detection Time-of-Flight (GC/TOF-MS).
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Waters, Laura S. "Comparison of two methods for differentiating negative from inconclusive GC-MS test results using an isotopic analog of the analyte as the internal standard -- 11-nor-[delta]⁹-tetrahydrocannabinol-9-carboxylic acid example." Birmingham, Ala. : University of Alabama at Birmingham, 2008. https://www.mhsl.uab.edu/dt/2008m/waters.pdf.
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Wang, Ting. "Monitoring a natural autoxidation process of methyl linoleate by using GC-MS : a thesis." Scholarly Commons, 2001. https://scholarlycommons.pacific.edu/uop_etds/586.
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The methyl ester of an unsaturated fatty acid, methyllinoleate was reacted with oxygen in a pressurized system at a controlled temperature. A natural autoxidation of methyl linoleate was observed without the addition of an initiating reagent. This autoxidation process could be used to mimic the course of lipid peroxidation, which is the major cause ofradical damage to living cells. The technology of GC-MS was employed to monitor the autoxidation of methyllinoleate.
Eight of the autoxidation products separated by GC column were identified by interpreting the corresponding EI ion mass spectra. The products from 9-alkoxy methyl linoleate radical were methyl octanate, 2,4-decadienal, nonanoic acid, 9-oxo-methyl ester, and its further oxidation product, nonanedioic acid, monomethyl ester. All of them formed through a pathway of beta-cleavage. The products from 13-alkoxy methyl linoleate radical were tridecanoic acid, 9, 11-diene-13-oxo-methyl ester, hex anal, and its further oxidation product, hexanoic acid. They were also formed through a mechanism of beta-cleavage. The fourth product from 13-alkoxy methyllinoleate radical was 13-keto-9, 11-octadecadienoic acid, methyl ester, which was obtained through a pathway of keto formation. Observation of their concentrations in the samples at different autoxidation periods revealed the time-course of formation of these products.
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FURLAN, NATALIE S. "Estudos sobre a recentidade de documentos utilizando-se a tecnica de cromatografia a gas acoplada a espectrometria de massas (GC-MS)." reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9358.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
FAPESP:05/58301-0
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RAMMUTHU, DHANUKA. "Rapid and simple gas chromatography-mass spectrometry method for quantification of methylmalonic acid in plasma and urine: its application to the diagnosis of methylmalonic acidurias." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2010. http://hdl.handle.net/2108/1240.
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L’aciduria metilmalonica rappresenta un gruppo di acidurie organiche che comprendono principalmente difetti metabolici della metilmalonil-CoA mutasi e difetti del metabolismo della cobalamina.
Le acidurie metilmaloniche (MMAs) sono un gruppo eterogeneo di errori congeniti del metabolismo caratterizzate biochimicamente dall’accumulo di metilmalonato nelle urine e in altri fluidi corporei. Le MMAs che coinvolgono esclusivamente l’attività enzimatica della metilmalonil-CoA mutasi (mut0, mut - ,cblA and cblB) sono definite MMAs isolate. I difetti che influiscono sul metabolismo della metilcobalamina (MeCbl), cofattore di più cicli metabolici, presentano un contemporaneo accumulo di acido metilmalonicico ed omocistinuria (cblC,cblD,cblF).
Sebbene l’eziologia delle acidurie metilmaloniche sia eterogena il quadro clinico dei pazienti é simile.
Nella maggior parte dei pazienti la sintomatologia si presenta, in età neonatale, con vomito ricorrente, disidratazione, epatomegalia, sofferenza respiratoria, ipotonia muscolare e progressiva alterazione dello stato di coscienza con probabile evoluzione in malattia ingravescente, coma profondo e morte.
Le alterazioni di laboratorio più importanti sono una severa cheto-lattico acidosi, un’ ipo o iperglicemia, una neutropenia, un’iperglicinemia ed un’iperammoniemia che, se non corrette con un pronto e specifico intervento terapeutico possono portare a gravi handicap o morte.
Abbiamo sviluppato un metodo rapido e sensibile in cromatografia gassosa e spettrometria di massa utilizzando il metodo di diluizione isotopica per la quantificazione dell’acido metilmalonico nelle urine e nel plasma, utile per la diagnosi delle MMAs e nel follow up.
La diluizione isotopica con isotopi stabili è considerato il metodo gold standard per la misurazione dei metaboliti perché essendo l’isotopo lo standard ideale, risolve il problema dell’ efficienza dell’estrazione nei metodi che si avvalgono dell’ estrazione con solvente.
Il metodo richiede fasi successive: l'estrazione dalle urine e dal plasma con estrazione liquido-liquido, l'essiccazione dell’estratto e infine la derivatizzazione con BSTFA dei prodotti di estrazione per formare i trimetilsilil derivati prima di essere iniettati nel GC/MS.
Il metodo è stato validato seguendo un piano che comprende il campo di applicazione del metodo, le caratteristiche di efficacia del metodo e dei suoi limiti di accettazione.
I parametri esaminati nel processo di validazione sono stati: limite di rivelazione e quantificazione, accuratezza, precisione, linearità e il recupero del MMA.
Per il MMA plasmatico con l’aggiunta dell’analita, il limite di rilevazione o il limite del bianco (media più 3 SD del bianco) è stato di 0,1 µmol/l ed il limite di quantificazione (media più 10 SD del bianco) 0.8 µmol/l; per il MMA urinario con l’aggiunta dell’analita, il limite di rilevazione o limite del bianco (media più 3 SD del bianco) è stato di 0,1 µmol/l ed il limite di quantificazione (media più 10 SD del bianco) 0,7 µmol/l. Il range di linearità per le urine ed il plasma è compreso tra 0,1-400 µmol/l.
I valori normali di acido metilmalonico (plasma e urine) sono stati ottenuti da 50 pazienti sani di controllo. Il metodo è stato validato clinicamente analizzando 10 campioni prelevati da pazienti con tre varianti fenotipiche della aciduria metilmalonica. Il metodo oltre alla suo uso nella routine clinica potrebbe essere utilizzato come metodo nei programmi screening.Methylmalonic aciduria is a group of organic aciduria associated with methylmalonyl-CoA mutase and cobalamin metabolic defects. Methylmalonic acidurias (MMAuria) are a heterogeneous group of inborn metabolic errors biochemically characterized by the accumulation of methylmalonate in urine and other body fluids. MMAuria exclusively affecting MCM activity (mut0,mut -,cblA and cblB) are termed isolated MMAuria. Some of these defects additionally affect the metabolism of methylcobalamin (MeCbl) resulting in combined MMA and homocysteinuria (cblC,cblD,cblF). Although the causes of Methylmalonic acidurias (MMAuria) are etiology, the clinical presentation of affected patients is similar. The majority of patients display early in life recurrent vomiting, dehydration, hepatomegaly, respiratory distress, muscular hypotonia and progressive alteration of consciousness, probably degenerating to overwhelming illness, deep coma and death. Severe combined keto-and lactic acidosis, hypo- or hyper-glycaemia, neutropenia, hyperglycinaemia and hyperammonaemia are the most important laboratory features. Without specific therapy these episodes result in severe handicap or death. We developed a rapid and sensible GC/MS method using stable isotope dilution to diagnose and quantify methylmalonic acid in urine and plasma. Stable isotope dilution is an ideal internal standard and is considered the gold standard method for measuring metabolites because it obviates the problem of varying levels of extraction efficiency by solvent extraction methods. Our methodology is capable of monitoring and quantifying MMA and it can follow up on and diagnose methylmalonic acidurias. The method requires a sequence of steps: extraction from urine and plasma using liquid–liquid extraction, drying, and finally derivatization by BSTFA of extraction products to form trimethylsilyl derivates prior to GC/MS injection. The method was validated. The validation follows a plan that includes the scope of the method, the method performance characteristics and its acceptance limits. Parameters examined in the validation process were limit of detection and quantification, reproducibility, linearity and recovery. For blood MMA with added analyte, the limit of detection or limit of the blank (mean plus 3 SD of blank) for was 0.1 µmol/l and the limit of quantification (mean plus 10 SD of blank) 0.8 µmol/l; For urine MMA with added analyte, the limit of detection or limit of the blank (mean plus 3 SD of blank) for was 0.1 µmol/l and the limit of quantification (mean plus 10 SD of blank) 0.7 µmol/l. For urine and plasma the linearity range was from 0.1 mol/l to 400 mol/l. Normal methylmalonic acid values were obtained from plasma and urine of 50 healthy control patients. The method was clinically validated by analyzed 10 samples from patients with three phenotypic variant of methylmalonic aciduria and therefore could be suitable for implementation in routine clinical screening programs and quantification environments.
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), Akin James (James J. "Characterization of human skin emanations by Solid Phase Microextraction (SPME) extraction of volatiles and subsequent analysis by Gas Chromatography-Mass Spectrometry (GC-MS)." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33399.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005.Includes bibliographical references (p. 80-82).
An experimental study was performed to develop and validate a collection and analysis protocol for human skin emanations. The protocol developed included the rubbing of glass beads on the palms and backs of hands for 20 minutes. The volatile headspace above samples were extracted by a solid-phase microextraction fiber which incorporated a composite coating of liquid polymer matrix and solid porous particles. This protocol provided robust and convenient signatures of human skin emanations and was applied to two experiments for validation. In one experiment, a set of twins donated samples and results suggested qualitative differences between samples of twins. The second experiment involved collections from four unrelated individuals over a period of one month. Multivariate analysis was applied to this data set and indicated a stable signature that can be ascribed to the individual, confirming that the protocol developed here can be extended to larger sample sets of MHC typed individuals.
by James Akin.
S.M.
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Oliveira, Justine Paula Ramos de. "Estudo dos poluentes orgânicos persistentes (POPs) em regiões industriais da Grande São Paulo - via cromatografia a gás acoplada a espectrometria de massas (GC-MS) e captura de elétrons (GC-ECD)." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-06062013-091439/.
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O estudo objetivou desenvolver e validar um método para identificar e quantificar poluentes orgânicos persistentes, conhecidos como POPs, em solo de regiões industriais dos municípios de Caieiras e Franco da Rocha SP, via cromatografia a gás acoplada a Espectrometria de Massas (GC-MS) e Detector por Captura de Elétrons (ECD). Em observância ao Tratado de Estocolmo, patrocinado pela Organização das Nações Unidas ONU, que prevê o banimento de pelo menos doze dos POPs, e no qual o Brasil é um dos 113 países signatários, o trabalho visou colaborar positivamente com essa questão ambiental tão importante. Estes compostos são tóxicos e altamente estáveis no ambiente e em organismos vivos, dentre os quais, são abordados nesse trabalho o clordano cis/trans (C10H6Cl8), o heptacloro (C10H5Cl7), o heptacloro epóxido cis/trans (C10H5Cl7) e os isômeros α-, β-, γ- e δ-BHC (C6Cl6). Para garantir a confiabilidade das análises realizadas, foram realizados ensaios de Validação da metodologia, com base nas diretrizes do INMETRO. A técnica de extração utilizada foi o QuEChERS, obtendo resultados de recuperação na faixa de 70 a 120% para a maioria dos compostos estudados, considerados aceitáveis para matrizes complexas. Os limites de detecção e quantificação do método compreenderam a faixa de 0,0002 e 0,01 μg.g1, respectivamente. As amostras analisadas apresentaram contaminação pelos compostos hexaclorobenzeno α-, β-, γ- e δ-, muitas das quais estão acima dos limites máximos permissíveis, de acordo com as legislações nacionais e internacionais vigentes.The study aimed to develop and validate a method to identify and quantify persistent organic pollutants, known as POPs in soil of industrial regions Caieiras and Franco da Rocha municipalities in São Paulo, via gas chromatography coupled with Mass Spectrometry (GC-MS) and Electron Capture Detector (ECD). In compliance with the Treaty of Stockholm, sponsored by the United Nations - UN, which provides for a ban of at least twelve POPs, in which Brazil is one of the 113 signatory countries, the work aims to contribute positively to the environmental issue as important . These compounds are highly toxic and stable in the environment and living organisms, among which are address in this work chlordane cis / trans (C10H6Cl8), heptachlor (C10H5Cl7), heptachlor epoxide the cis / trans (C10H5Cl7) and the isomers α-, β-, γ- and δ-BHC (C6Cl6). To ensure reliability of the analysis carried out, tests were carried out validation method, based on the guidelines of INMETRO. The extraction technique was used QuEChERS, achieving recovery in the range 70 to 120% for the most of compounds, acceptable for complex matrices. The limits of detection and quantification of the method comprises the range of 0.0002 and 0.01 μg.g-1, respectively. The samples analyzed were contaminated by compounds hexachlorobenzene α-, β-, γ- and δ-, many of which are above the maximum allowable in accordance with national legislation and international law.
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Ballentine, Regina. "Chemical Characterization of Pseudognaphalium obtusifolium by Gas Chromatography - Mass Spectrometry (GC-MS) to Assess Potential Therapeutic Phytochemicals and Toxicological Concerns Using Simulated Use Conditions." VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/6052.
Full textAbstract:
Chemical Characterization of Pseudognaphalium obtusifolium by Gas Chromatography – Mass Spectrometry (GC-MS) to Assess Potential Therapeutic Phytochemicals and Toxicological Concerns Using Simulated Use Conditions
By Regina Ballentine
Virginia Commonwealth University, 2019
Director: Sarah C. Rutan, Professor, Department of Chemistry
Currently, there is an increasing demand for natural therapies and herbal products to treat various ailments. It is generally believed that natural therapies have fewer side-effects than traditional western medicine; however, they are often used in different strengths and formulations without consistency of the levels of target compounds or knowledge about toxicity. Due to this growing trend, a comprehensive chemical evaluation of plants used for medicinal purposes is necessary.
Pseudognaphalium obtusifolium is a plant that has been used historically by Native Americans as an herbal medicine. It is a flowering plant belonging to the Asteraceae family indigenous to the Eastern United States. There are documented accounts of the Native Americans using the herb therapeutically. Reportedly, they used the plant to prepare tea and as filler for bedding. Additionally, they smoked the plant material.
To date, there has been little research published on the chemical composition of this plant. Thus, the objective of this work was to conduct a chemical survey of P. obtusifolium using methodologies that would simulate the three historical routes of administration (tea, bedding material, and smoke inhalation).
To determine the types of compounds that may be found in the plant, initial experiments using pressurized solvent extraction (PSE) with an ethanolic solvent were performed followed by analysis using gas chromatography – mass spectrometry (GC-MS) in scan mode. This extraction technique enabled a broad range of compounds to be identified.
For the analysis of the tea, the leaves and the flowers were ground and analyzed separately. The “tea” simulation was then performed using a water extraction which was then back extracted into dichloromethane for GC-MS analysis in Selected Ion Monitoring (SIM) mode. Seventeen target compounds (terpenes, terpinoids, flavanoids, etc.) were quantified using this method.
A bedding material simulation was performed using headspace solid phase micro-extraction (HS-SPME) to collect the volatile and/or semi-volatile components of the headspace. The compounds collected on the SPME fiber were then analyzed by GC-MS in scan and SIM modes to qualitatively and quantitatively determine the types of chemical compounds (most of which were terpenes) that may be off-gassed from bedding material. This analysis compared levels of compounds in two different crop years and four terpene compounds were quantified.
To simulate smoking of the plant material, the leaves and flowers were fashioned into smoking articles. Sample collection was performed by a smoking machine and smoke condensate was collected. The smoke condensate was then analyzed by GC-MS in scan mode. As combustion and pyrolysis of plant material are known to produce toxic products, specific potentially harmful compounds were investigated and quantified.
This chemical analysis of P. obtusifolium identified target compounds that can be found in the three simulated usage forms. Identification of these compounds gives insight on why the Native Americans may have used P. obtusifolium as an herbal medicine. Among the detected compounds, there were many unknowns. Elucidating these unknown compounds will be important in the effort to understand the full chemical profile of this plant.
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Wang, Minkun. "Topic Model-based Mass Spectrometric Data Analysis in Cancer Biomarker Discovery Studies." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/78201.
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Identification of disease-related alterations in molecular and cellular mechanisms may reveal useful biomarkers for human diseases including cancers. High-throughput omic technologies for identifying and quantifying multi-level biological molecules (e.g., proteins, glycans, and metabolites) have facilitated the advances in biological research in recent years. Liquid (or gas) chromatography coupled with mass spectrometry (LC/GC-MS) has become an essential tool in such large-scale omic studies. Appropriate LC/GC-MS data preprocessing pipelines are needed to detect true differences between biological groups. Challenges exist in several aspects of MS data analysis. Specifically for biomarker discovery, one fundamental challenge in quantitation of biomolecules is owing to the heterogeneous nature of human biospecimens. Although this issue has been a subject of discussion in cancer genomic studies, it has not yet been rigorously investigated in mass spectrometry based omic studies. Purification of mass spectometric data is highly desired prior to subsequent differential analysis.
In this research dissertation, we majorly target at addressing the purification problem through probabilistic modeling. We propose an intensity-level purification model (IPM) to computationally purify LC/GC-MS based cancerous data in biomarker discovery studies. We further extend IPM to scan-level purification model (SPM) by considering information from extracted ion chromatogram (EIC, scan-level feature). Both IPM and SPM belong to the category of topic modeling approach, which aims to identify the underlying "topics" (sources) and their mixture proportions in composing the heterogeneous data. Additionally, denoise deconvolution model (DMM) is proposed to capture the noise signals in samples based on purified profiles. Variational expectation-maximization (VEM) and Markov chain Monte Carlo (MCMC) methods are used to draw inference on the latent variables and estimate the model parameters. Before we come to purification, other research topics in related to mass spectrometric data analysis for cancer biomarker discovery are also investigated in this dissertation.
Chapter 3 discusses the developed methods in the differential analysis of LC/GC-MS based omic data, specifically for the preprocessing in data of LC-MS profiled glycans. Chapter 4 presents the assumptions and inference details of IPM, SPM, and DDM. A latent Dirichlet allocation (LDA) core is used to model the heterogeneous cancerous data as mixtures of topics consisting of sample-specific pure cancerous source and non-cancerous contaminants. We evaluated the capability of the proposed models in capturing mixture proportions of contaminants and cancer profiles on LC-MS based serum and tissue proteomic and GC-MS based tissue metabolomic datasets acquired from patients with hepatocellular carcinoma (HCC) and liver cirrhosis. Chapter 5 elaborates these applications in cancer biomarker discovery, where typical single omic and integrative analysis of multi-omic studies are included.Ph. D.
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Seno, Hiroshi, Osamu Suzuki, Akira Ishii, Kei Zaitsu, Hideki Hattori, Tadashi Ogawa, and Masae Iwai. "SIMPLE AND RAPID ASSAY METHOD FOR SIMULTANEOUS QUANTIFICATION OF URINARY NICOTINE AND COTININE USING MICRO-EXTRACTION BY PACKED SORBENT AND GAS CHROMATOGRAPHY-MASS SPECTROMETRY." Nagoya University School of Medicine, 2013. http://hdl.handle.net/2237/18475.
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Claypoole, Sherri L. "Quantitation of 3-alkyl-2-methoxypyrazines in Grape Juice and Wine via SPME-GC/MS." Youngstown State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1279827076.
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Jordaan, Maraliese. "Diagnosis of helicobacter pylori infection with the 13C-urea breath test : analysis by means of gas chromatography with mass selective detection." Diss., University of Pretoria, 2007. http://hdl.handle.net/2263/27035.
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Jejdling, Julia. "Biomonitoring of soil remediation workers´ exposure to polycyclic aromatic compounds (PACs) – method development and characterisation of PACs in blood." Thesis, Örebro universitet, Institutionen för naturvetenskap och teknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-74387.
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For a long period of time, it has been common to use creosote for impregnation of railroad ties. Creosote consists of 85% polycyclic aromatic hydrocarbons (PAHs), of which some are carcinogenic and/or mutagenic. In 2016, a soil remediation process was commenced at an old impregnation facility in Sweden and both dermal, urine and blood samples were taken from soil remediation workers to investigate the occupational exposure. The objectives of this study were to develop a method for the extraction of polycyclic aromatic compounds (PACs), including PAHs, oxy-PAHs, alkylated PAHs and dibenzothiophenes and azaarenes from blood, and to quantify PAHs in the collected blood samples from the soil remediation workers. In the method development, two parameters were tested: centrifugation of samples before extraction and use of either basic or deactivated silica in the clean-up step of the blood extracts. The results showed that the best method was without centrifugation and with use of basic silica. Results from the analysis of the soil remediation workers´ blood showed PAHs in average concentrations of 0.05-6.47 ng/mL blood, with fluorene and biphenyl being the most abundant PAHs. The occupational groups (office, machine and sampling) had similar average concentrations of PAHs, with office workers being slightly less exposed. The PAHs blood profile did not reflect the PAHs profiles in contaminated soil from the area; the blood profiles had relatively higher abundances of low molecular weight PAHs, while the soils had higher relative concentrations of middle molecular weight PAHs. Both blood and soils had low relative concentrations of high molecular weight PAHs. Pyrene concentrations in blood and 1-hydroxypyrene metabolite concentrations in urine samples showed no correlation (linearity r2=0.045). Both blood and urine samples from the workers indicated a low exposure of PAHs. The method tested in this study can be used for analysis of a broad range of PACs and seems to be a better approach for studying the exposure of PACs than today’s methods analysing a few urine metabolites. But additional clean-up is suggested to improve the quantification of all blood samples. Further investigations are required to gain an understanding of normal, unexposed PACs levels in blood.
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Tollbäck, Petter. "Large Volume Injection and Hyphenated Techniques for Gas Chromatographic Determination of PBDEs and Carbazoles in Air." Doctoral thesis, Stockholm University, Department of Analytical Chemistry, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-367.
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This thesis is based on studies in which the suitability of various gas chromatography (GC) injection techniques was examined for the determination of polybrominated diphenyl ethers (PBDEs) and carbazoles, two groups of compounds that are thermally labile and/or have high boiling-points. For such substances, it is essential to introduce the samples into the GC system in an appropriate way to avoid degradation and other potential problems. In addition, different types of gas chromatographic column system and mass spectrometric detectors were evaluated for the determination of PBDEs.
Conventional injectors, such as splitless, on-column and programmed temperature vaporizing (PTV) injectors were evaluated and optimized for determination of PBDEs. The results show on-column injection to be the best option, providing low discrimination and high precision. The splitless injector is commonly used for “dirty” samples. However, it is not suitable for determination of the high molecular weight congeners, since it tends to discriminate against them and promote their degradation, leading to poor precision and accuracy. The PTV injector appears to be a more suitable alternative. The use of liners reduces problems associated with potential interferents such as polar compounds and lipids and compared to the hot splitless injector, it provides gentler solvent evaporation, due to its temperature programming feature, leading to low discrimination and variance.
Increasing the injection volume from the conventional 1-3 µL to >50 µL offers two main benefits. Firstly, the overall detection and quantification limits are decreased, since the entire sample extract can be injected into the GC system. Secondly, large volume injections enable hyphenation of preceding techniques such as liquid chromatography (LC), solid phase extraction and other kinds of extraction. Large-volume injections were utilized and optimized in the studies included in this thesis.
With a loop-type injector/interface large sample volumes can be injected on-column providing low risk of discrimination against compounds with low volatility. This injector was used for the determination of PBDEs in air and as an interface for the determination of carbazoles by LC-GC. Peak distortion is a frequently encountered problem associated with this type of injector that was addressed and solved during the work underlying this thesis.
The PTV can be used as a large volume injector, in so-called solvent vent mode. This technique was evaluated for the determination of PBDEs and as an interface for coupling dynamic sonication-assisted solvent extraction online to GC. The results show that careful optimization of the injection parameters is required, but also that the PTV is robust and yields reproducible results.
PBDEs are commonly detected using mass spectrometry in electron capture negative ionization (ECNI) mode, monitoring bromine ions (m/z 79 and 81). The mass spectrometric properties of the fully brominated diphenyl ether, BDE-209, have been investigated. A high molecular weight fragment at m/z 486/488 enables the use of 13C-labeled BDE-209 as an internal surrogate standard.
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Brettell, Rhea C. "The final masquerade : a molecular-based approach to the identification of resinous plant exudates in Roman mortuary contexts in Britain and evaluation of their significance." Thesis, University of Bradford, 2016. http://hdl.handle.net/10454/15886.
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This study provides chemical confirmation for the use of resinous plant exudates in mortuary contexts in Roman Britain. Analysis of amorphous masses, adhering residues and grave deposits using gas chromatography-mass spectrometry has revealed terpenoid biomarkers in sixteen inhumation and two cremation burials. The natural products characterized include European Pinaceae (conifer) resins, Pistacia spp. (mastic/terebinth) resins from the Mediterranean or the Levant and Boswellia spp. (frankincense) gum-resins from southern Arabia or eastern Africa. In addition, traces of a balsamic resin, probably Liquidambar orientalis, have been identified. A correlation between the use of these exotic exudates and interment in substantial, often multiple, containers with high-quality textiles and grave goods was observed. Theoretical consideration of this imported rite illuminates the multiplicity of roles played by resins/gum-resins in the mortuary sphere. The material properties of these highly scented substances speak to the biological reality of the decomposing body and to the socially constructed identity of the individual. On a practical level, they acted as temporary preservatives and masked the odour of decay. As social signifiers, they denoted the status of the deceased and promoted remembrance through conspicuous consumption and sensory impact. Encoded with ritual meaning, they purified the body and facilitated the final rite of passage to the afterlife. The recovery of these resinous traces provides us with new insights into the treatment of the body in the Roman period and establishes fresh links between the remote province of Britannia and the remainder of the Empire.
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Ghiselli, Gislaine. "Avaliação da qualidade das aguas destinadas ao abastecimento publico na região de Campinas : ocorrencia e determinação dos interferentes endocrinos (IE) e produtos farmaceuticos e de higiene pessoal (PFHP)." [s.n.], 2001. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249644.
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Orientador: Wilson de Figueiredo JardimTese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
Made available in DSpace on 2018-08-07T20:01:49Z (GMT). No. of bitstreams: 1 Ghiselli_Gislaine_D.pdf: 7893135 bytes, checksum: 77abd572fbade3721ea074ed0616e34b (MD5) Previous issue date: 2006
Doutorado
Quimica Analitica
Doutor em Quimica
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Xu, Zhanfeng. "Prediction and Classification of Physical Properties by Near-Infrared Spectroscopy and Baseline Correction of Gas Chromatography Mass Spectrometry Data of Jet Fuels by Using Chemometric Algorithms." Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1336436389.
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Brigante, Tamires Amabile Valim. "Desenvolvimento de polímeros de impressão molecular para microextração em ponteiras de bisfenol A em amostras de urina e análise por GC-MS." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/60/60134/tde-28102015-162437/.
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O Bisfenol A (BPA, acrônimo da língua inglesa - bisphenol A) é uma substância utilizada na fabricação de embalagens alimentícias e resinas odontológicas. Sua toxicidade deve-se ao fato de que, como disruptor endócrino, afeta o sistema reprodutor, cardiovascular, neuro-endócrino e pode apresentar potencial carcinogênico. Em métodos bioanalíticos, o preparo da amostra tem sido requerido para aumentar a seletividade e sensibilidade analítica, através da remoção dos interferentes da amostra biológica e concentração dos analitos, quase sempre presentes em níveis de traços. A microextração em ponteiras (DPX, acrônimo das iniciais em língua inglesa - Disposable Pipette Extraction), baseada no equilíbrio de sorção do soluto com a fase extratora, consiste em uma ponteira padrão de micropipeta modificada, na qual o sorvente está contido livremente entre dois filtros, permitindo rápida extração do analito em diferentes matrizes complexas. Os polímeros de impressão molecular (MIP acrônimo das iniciais em língua inglesa - Molecularly Imprinted Polymer) consistem em uma rede polimérica tridimensional que possui cavidades seletivas para o reconhecimento molecular do analito ou de substâncias de estrutura análoga. Essa rede polimérica é sintetizada ao redor da substância molde (analito), e a cavidade seletiva é formada após a remoção do molde. As vantagens do processo sol-gel para a síntese do MIP são o controle do tamanho e forma das partículas, ajuste da hidrofobicidade e alta estabilidade térmica. No presente trabalho, o MIP foi sintetizado e utilizado como sorvente para a técnica DPX para a determinação de bisfenol A em amostras de urina por cromatografia em fase gasosa acoplada à espectrometria de massas (GC-MS, acrônimo das iniciais em língua inglesa - Gas Chromatography coupled to Mass Spectrometry). O MIP foi sintetizado pela via sol-gel utilizando aminopropiltrietoxisilano (APTES) como mônomero funcional e tetraetil-orto-silicato (TEOS) como reagente de ligação cruzada. Como molde foram avaliados o BPA para o MIP, e o tetrabromobisfenol A (TBBPA) para o polímero molecularmente impresso com molécula análoga ao analito (DMIP, acrônimo das iniciais em língua inglesa - Dummy Molecularly Imprinted Polymer). Para avaliar a seletividade do MIP, o polímero não impresso (NIP, acrônimo das iniciais em língua inglesa - Non-imprinted Polymer) foi sintetizado seguindo o mesmo procedimento de síntese do MIP com exceção da adição da molécula molde. Apesar de a capacidade de sorção do MIP ser ligeiramente maior, o DMIP foi selecionado como sorvente para minimizar o efeito de memória. O DMIP foi caracterizado por microscopia eletrônica de varredura (MEV) e por espectroscopia vibracional na região do infravermelho por transformada de Fourier (FTIR, acrônico das inicias em língua inglesa - Fourier Transform Infrared). Os parâmetros da técnica DPX, tais como, o tempo de equilíbrio de sorção entre a amostra e o sorvente e condições de dessorção foram otimizadas por técnicas quimiométricas. A robustez do DMIP sintetizado via sol-gel foi comprovada pela reutilização deste sorvente por mais de 100 vezes, sem perda da eficiência da extração. O método desenvolvido DPX/GC-MS apresentou linearidade na faixa de 50 a 500 ng mL-1, precisão com CV (coeficientes de variação) entre 4 e 14% e de exatidão com valores de erro padrão relativo (EPR) de -13,6 a 12,3%. O método de referência utilizando a extração líquido-líquido e GC-MS (LLE/GC-MS), faixa de linearidade de 5 a 50 ng mL-1, foi desenvolvido e validado. Embora o método DPX/GC-MS inovador, quando comparado ao LLE/GC-MS, tenha apresentado maior limite de quantificação, apresentou as seguintes vantagens: simplicidade, rapidez e utilização de menores volumes de amostra e de solventes orgânicos na etapa do preparo da amostraBisphenol A (BPA) is widely used in food package and dental resins manufacturing. Its toxicity is due to its endocrine disruptor activity that affects the reproductive, cardiovascular, neurological system and may have carcinogenic potential. In bioanalytical methods the sample preparation has been required to increase the selectivity and analytical sensibility by removing the interfering from the biological matrix and concentration of the analytes that are in trace levels most of the times. The disposable pipette extraction (DPX) is based on sorption equilibrium of the analyte between the sample and the extraction phase. It consists in a pipette that contais the sorbent phase freely between two filters. Then, the extraction of the solute from the complex sample occurs quickly. Molecularly imprinted polymer is a tridimensional polimeric network that has selectivity cavities that can recognize an analyte or a substance with a similar structure. The polimeric network is synthesized around to a template molecule and after removing this template, a selective cavity is formed. The advantages of the sol-gel process for the synthesis of MIP are the control of the size and shape of the particles, hydrophobicity adjustment and high thermal stability. In the present study MIP was synthesized and used as sorbent to DPX method for determination of BPA in urine samples by gas chromatography coupled to mass spectrometry (GC-MS). Sol-gel methodoly was used to synthesize the polymers. Aminopropyltriethoxysilane (APTES) was used as a functional monomer and tetraethyl orthosilicate (TEOS) as crosslinking reagent. BPA and tetrabromobisphenol A (TBBPA) were evaluated as template to the synthesis of MIP and dummy molecularly imprinted polymer (DMIP) which is a molecularly imprinted polymer that uses a template structurally similar to the analyte. The non-imprinted polymer (NIP) was synthesized following the same procedure that MIP, except for the addition of template. It was made to verify the improvement of selectivity and sensibility of molecularly imprinted polymers. Although the sorption capacity of the MIP is slightly larger, DMIP has been selected as a sorbent in order to minimize the memory effect. The DMIP was characterized by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared spectroscopy (FTIR). The parameters of DPX, such as time sorption equilibrium between the sample and the sorbent and desorption conditions were optimized by chemometrics. Robustness of DMIP sinthesized by sol-gel process was evidenciated for the reuse of DMIP for more than a 100 times. The developed method DPX/GC-MS showed linearity on the range from 50 to 500 ng ml-1, precision values with coefficient of variation (CV) betweeen 4 and 14% and accuracy with relative standard deviation values (RSD) from -13.6 to 12.3%. The reference method using liquid- liquid extraction and GC-MS (LLE/GC-MS) was developed and validated, showing linearity from 0.5 to 50 ng mL-1. Althout the innovative method DPX/GC-MS has showed limit of quantification larger than LLE/GC-MS, it presents the following advantages: simplicity, rapidy and utilization of smaller volumes of organic solvents on the sample preparation step
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Tobiášová, Tereza. "Studium průniku vybraných degradačních produktů syntetických polymerů do životního prostředí." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2008. http://www.nusl.cz/ntk/nusl-216452.
Full textAbstract:
The subject of this thesis is the study of the degradation of polyurethanes in the weather conditions on the waste dumps and observation of the penetration of the potential degradation products into the environment.
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Wehmer, Kathrine. "Keramikk - fortidens stemme : Lipidanalyse på keramikk fra Påtåker, Sollentuna, Uppland, Sverige." Thesis, Stockholms universitet, Institutionen för arkeologi och antikens kultur, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-144240.
Full textAbstract:
This paper is about food culture in Uppland under early iron age in Upplans, Sverige. Gas chromatography–mass spectrometry (GC-MS) was used to analysis the lipids that were extracted from archaeological potsherds from Påtåker Raä 62, Sollentuna, Uppland. The result of the lipid analysis shows content of aquatic animal products, terrestrial animal products, vegetables and indication of being heated. Based on these results and what is considered to be a normal diet during the Iron Age, it is possible to say that there are similarities. These results are also compared with three sites from Late Iron Age – Vendel 1:1, Vendel 28 and Tuna, to see if there are any similarities. The reason to choose three sites from Late Iron Age, and not Early Iron Age, is because there haven’t been done studies like this on material from the early Iron Age. Vendel 28 was the site that was most similar to Påtåker, when it comes to its enviorment with meadows and woods, and the ceramics application areas.This study is part of the on going research of Påtåker Raä 62, Sollentuna, Oppland.
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Fransson, Rasmus. "Determination of FAME in Gasoline : A Fuel Quality Analysis." Thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-21212.
Full textAbstract:
Gasoline is produced by distilling petroleum oil. This is done at a refinery, where a lot of other products are produced as well. With increasing interest in bio-fuels the fuel companies started to produce substances such as biodiesel as well as the petroleum-based fuels. These products are then transported to where they are going to be used or sold, there included both gasoline, which is a petroleum-based fuel, and biodiesel (FAME), which in Sweden is based on rapeseed oil. If the vessel for transporting gasoline, or pipeline/connections filling and emptying the tanks, has previously been used for biodiesel, there is a risk of contaminating the gasoline with biodiesel. This contamination can have a lot of different effects such as either clogging filters or injectors in both gasoline- and ethanol-based engines, or even change the properties and therefore quality of the fuel. To ensure that the results from tests and research involving gasoline can be used and compared with each other, the quality of the fuel must have the same properties throughout all tests. This is controlled by taking samples on a regular basis and analyzing the quality and level of impurities in the fuel used in that specific test. Screening for FAME is therefore necessary which is where this thesis becomes relevant. This thesis was carried out with the purpose to develop a new or verify an already developed method to quantify FAME in gasoline. To determine the FAME content, a standard gas chromatography method, IP 585, was used. It was changed to fit in this application, since it was originally made to determine FAME content in diesel, not gasoline. It was concluded that it was possible to determine the FAME content in gasoline when IP 585 was used as is. There were some possible alternatives to IP 585 and they will be discussed in the literature study.Bensin framställs genom destillation av råolja. Detta görs på ett raffinaderi där ett flertal andra produkter också utvinns. På senare tid har ögonen öppnats för "biobränslen", bland annat biodiesel. Det händer därför att detta också framställs på samma plats som bensinen. Dessa produkter säljs sedan och brukar fraktas i stora tankar till företagen som köpt dem. Ifall tankarna vid transport eller rören bränslet går igenom till tankarna först använts till biodiesel och sedan används till bensin finns det stor risk att en del biodiesel hamnar i bensinen. Detta kan leda till en rad olika problem. Ett exempel är att biodieseln kan sätta igen och förstöra injektorer i bensin- och etanolmotorer. Det kan även påverka testresultat i olika testriggar, vilket är ett av fallen på Volvo. Ifall bränslet inte bibehåller samma kvalitet för varje test det används i leder det till svårigheter vid jämförelser och resultatens riktighet. Det blir därför nödvändigt att kontrollera bensinens innehåll, där inräknat screening av FAME. Detta arbete utfördes med syftet att utveckla en ny eller verifiera en redan beprövad metod för att bestämma koncentrationen FAME i bensin. För att mäta koncentrationen FAME användes en standardmetod till GC-MS, IP 585. Den modifierades något för att passa in i denna applikation då den från början var gjord för kvantifiering i diesel och inte bensin. Slutsatsen drogs att det är möjligt att mäta koncentrationen FAME i bensin med IP 585 använd som den är. Det fanns möjliga alternativ till metoden, dessa bemöts i litteraturstudien.
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Lai, Sin Pin. "Furan measurement in transformer oil by UV-Vis spectroscopy using fuzzy logic approach." Thesis, Curtin University, 2009. http://hdl.handle.net/20.500.11937/2342.
Full textAbstract:
An Ultraviolet to Visible (UV-Vis) spectroscopic analysis based on fuzzy logic approach has been developed for furan content measurement in transformer oil. Following the successful identification and quantification of furan derivatives in transformer oil by ASTM D5837 standard, the new approach is able to approximate the furan content more conveniently and economically. As furan concentration level would determine the absorption intensity in UV-Vis spectral range, the fuzzy logic software model developed would exploit this characteristic to aggregate the furans content level in transformer oil. The UV-Vis spectral response at other ambient temperature is also studied. The proposed technique provides a convenient alternative to conventional method of furan measurement by High Performance Liquid Chromatography (HPLC) or Gas Chromatography Mass Spectrometry (GC/MS) in ASTM D5837 Standard.
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Nohelová, Gabriela. "Bisfenol A ve vodním ekosystému." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2014. http://www.nusl.cz/ntk/nusl-217085.
Full textAbstract:
This diploma thesis deals with Bisphenol A, especially with its impact on the aquatic ecosystem. Information about its properties, production and current use are summarized here. Its harmful impact on the environment, especially on the aquatic ecosystem and the human body is characterized. Also the methods of its degradation within the aquatic environment have been described. A summary of the options of a determination of Bisphenol A in water samples is incorporated and the method of gas chromatography with mass spectrometry (GC/TOF MS) and comprehensive two-dimensional gas chromatography with mass spectrometry (GCxGC/TOF-MS) is compared in the experimental part. Analytical determination precedes the isolation of the analyte from the water samples by solid phase extraction (SPE) using SupelcleanTM ENVITM - 18 and derivatization using the silylation reagent, N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA). The result of this work is the analysis of a series of real samples from wastewater treatment plants Brno Modřice and Luhačovice by a two-dimensional gas chromatography with mass spectrometry (GCxGC/TOF-MS).
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Abdel-Ghani, Mona H. "A Multi-instrument Investigation of Pigments, Binders and Varnishes from Egyptian Paintings (AD 1300-1900): Molecular and Elemental Analysis Using Raman, GC-MS and SEM-EDX Techniques." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/4315.
Full textAbstract:
The focus of this study was analytical investigations of Egyptian paintings, mainly
Coptic icons and Islamic wooden ceilings, dating from 1300-1900 using multiinstrumental
techniques. Twenty three Coptic icons and three wooden ceilings dated
from different periods and painted by different painters in case of icons were examined.
The materials used including pigments, media, varnishes, ground layers and gold layers.
The surface stratigraphy of paint samples, their layered structured and the composition
of materials used in each layer were analysed. Variations in painting techniques,
pigments palettes, paint media and varnishes applied in Egyptian paintings according to
painters, time and type of paintings were revealed.
A total of twenty-eight organic and inorganic pigments were identified in this study, of
which nine have never been previously included as a part of the Egyptian pigment
palettes, namely; smalt, lapis lazuli, indigo, pararealgar, Prussian blue, chrome yellow,
barium yellow, barium white and hydromagnesite. The identification of
hydromagnesite, which has never been to date considered as a pigment either in Egypt
or elsewhere and the identification of smalt from the mid-14th century, whose reported
earliest large scale use was in the 16th century. Two types of resins were identified as a
constituent of the oil/resin varnish applied on Coptic icons of which Venice turpentine
has been identified for the first time as an ingredient of Egyptian varnishes. The
identification of mosaic gold in an 18th C. icon, a novel usage of dammar resin and the
multilayered structure of the white ground layers were revealed.Egyptian Ministry of Higher Educations
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Abdel-Ghani, Mona Hussien. "A multi-instrument investigation of pigments, binders and varnishes from Egyptian paintings (AD 1300-1900) : molecular and elemental analysis using Raman, GC-MS and SEM-EDX techniques." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/4315.
Full textAbstract:
The focus of this study was analytical investigations of Egyptian paintings, mainly Coptic icons and Islamic wooden ceilings, dating from 1300-1900 using multi-instrumental techniques. Twenty three Coptic icons and three wooden ceilings dated from different periods and painted by different painters in case of icons were examined. The materials used including pigments, media, varnishes, ground layers and gold layers. The surface stratigraphy of paint samples, their layered structured and the composition of materials used in each layer were analysed. Variations in painting techniques, pigments palettes, paint media and varnishes applied in Egyptian paintings according to painters, time and type of paintings were revealed. A total of twenty-eight organic and inorganic pigments were identified in this study, of which nine have never been previously included as a part of the Egyptian pigment palettes, namely; smalt, lapis lazuli, indigo, pararealgar, Prussian blue, chrome yellow, barium yellow, barium white and hydromagnesite. The identification of hydromagnesite, which has never been to date considered as a pigment either in Egypt or elsewhere and the identification of smalt from the mid-14th century, whose reported earliest large scale use was in the 16th century. Two types of resins were identified as a constituent of the oil/resin varnish applied on Coptic icons of which Venice turpentine has been identified for the first time as an ingredient of Egyptian varnishes. The identification of mosaic gold in an 18th C. icon, a novel usage of dammar resin and the multilayered structure of the white ground layers were revealed.
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Gokmen, Pinar. "Evaluation Of Persistent Organic Pollutants (pops) In Balikesir Dam Lake Sediments." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612916/index.pdf.
Full textAbstract:
In this study, the Persistent Organic Pollutants (POPs) specifically17 Organochlorine Pesticides (OCPs) and 19 Polycyclic Aromatic Hydrocarbons (PAHs) were evaluated in the sediment samples of Balikesir (Ikizcetepeler) Dam Lake. Sixteen sampling points were chosen for determination of concentrations of OCPs and PAHs After ultrasonic bath extraction of the sediment samples GC-MS was used as analytical tool. Extraction efficiencies changes from 63.8 to 87.4% depending on the type of the POPs. Average OCP concentration was found in the range of 3.33-379 µ
g/kg a, average PAH concentration was found in the range of 3.28-32.9 µ
g/kg. Pollution maps regarding OCP and PAH distributions were drawn and the correlation between these two pollutant types was investigated. The quality control (QC) and quality assurance tests were applied by the analysis of standard reference materials (SRMs), surrogate standards and analysis replicates.
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Lai, Sin Pin. "Furan measurement in transformer oil by UV-Vis spectroscopy using fuzzy logic approach." Curtin University of Technology, Department of Electrical and Computer Engineering, 2009. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=128452.
Full textAbstract:
An Ultraviolet to Visible (UV-Vis) spectroscopic analysis based on fuzzy logic approach has been developed for furan content measurement in transformer oil. Following the successful identification and quantification of furan derivatives in transformer oil by ASTM D5837 standard, the new approach is able to approximate the furan content more conveniently and economically. As furan concentration level would determine the absorption intensity in UV-Vis spectral range, the fuzzy logic software model developed would exploit this characteristic to aggregate the furans content level in transformer oil. The UV-Vis spectral response at other ambient temperature is also studied. The proposed technique provides a convenient alternative to conventional method of furan measurement by High Performance Liquid Chromatography (HPLC) or Gas Chromatography Mass Spectrometry (GC/MS) in ASTM D5837 Standard.
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Fumes, Bruno Henrique. "Avaliação do emprego da técnica MEPS na análise de agrotóxicos em caldo de cana-de-açúcar por GC-MS." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/75/75135/tde-07052015-104934/.
Full textAbstract:
O uso de técnicas miniaturizadas de preparo de amostra vem se tornando uma tendência cada vez mais crescente em química analítica. Dentre elas o MEPS (Microextraction by a Packed Sorbent) apresenta grande potencial por poder ser acoplado on-line, sem grandes modificações, à cromatografia gasosa e líquida, não necessitando de grande quantidade de tempo para análise e seu cartucho sorvente ser reutilizável. O uso de MEPS, foi mais explorado até o presente momento na análise de fármacos em fluídos biológicos; dessa forma existe um pequeno número de publicações que exploram o uso dessa técnica na determinação de agrotóxicos em matrizes de alimentos. Por esse motivo, o presente trabalho teve como objetivo a avaliação do uso dessa técnica na determinação de seis agrotóxicos utilizados no cultivo da cana-de-açúcar (tebutiurom, carbofurano, atrazina, metribuzim, ametrina e bifentrina) em amostras de garapa. Para o desenvolvimento desse estudo foram verificadas dentre as variáveis pH, força iônica, solvente de eluição e volume do solvente de eluição, quais poderiam afetar o desempenho da técnica em diferentes fases extratoras, empregando nessa etapa de otimização planejamento fatorial fracionário 24-1. As fases avaliadas foram C18 Chromabond e HLB Oasis, assim como sistemas comercialmente disponíveis com as fases C18, C8, SAX, SCX e SIL. Durante essa etapa foi realizado um estudo inicial do uso do grafeno como material sorvente em MEPS, considerando as propriedades que esse material apresenta para atuar como adsorvente em técnicas de preparo de amostra. Contudo, o uso do grafeno apresentou entupimento no cartucho de sorção, problema ainda em avaliação. A fase C18 Chromabond foi a que apresentou os melhores resultados, sendo a escolhida para otimização dos parâmetros envolvidos na etapa de extração por MEPS. Os parâmetros otimizados por planejamento fatorial 23 foram os ciclos de: aspiração da amostra, lavagem e eluição. O método desenvolvido foi validado baseado nos critérios exigidos pelo MAPA e apresentou seletividade, linearidade e os limites de quantificação variaram de 2-10 μg/L. A recuperação foi adequada para todos os analitos (71,7-106,9%), assim como a precisão intra e inter-dia que apresentou coeficientes de variação (CV) menores que 16%. O método desenvolvido foi aplicado em quatro amostras reais de garapa de diferentes regiões.The use of miniaturized techniques in sample preparation has becoming a growing trend in analytical chemistry. Among these techniques MEPS (Microextraction by a Packed Sorbent) presents a great potential affording on-line coupling, without much modification to gas and liquid chromatography systems, in addition it does not require large analyses time and the sorbent cartridge is reusable. MEPS utilization has been explored mainly for drugs analyses in biological fluids, existing limited number of publications that apply this technique for pesticides analyses in food sample matrix. For this reason the goal of present work was the evaluation of MEPS in the analyses of six pesticides used in sugarcane cultivation (tebuthiuron, carbofuran, atrazine, metribuzine, ametryn and bifenthrin) in sugarcane juice samples. During the method development several variables were evaluated including pH, ionic strength, elution solvent and solvent volume, to determine which ones could affect the technique perform in different sorbent phases. For this optimization step, fractional factorial design 24-1 was utilized. Phases evaluated included C18 Chromabond and HLB Oasis, and also commercially available system containg C18, C8, SAX, SCX e SIL. During this step, it was also carried out an initial study employing graphene in a MEPS system; Tanking into account the properties that this material presents to act as adsorbent in sample preparation techniques. However the graphene showed obstruction problems in the sorption cartridge, whose solution is under way. The phase C18 Chromabond showed better results, and was chosen to MEPS parameters optimization. MEPs parameters optimized by full factorial desing 23 were the following cycles: sample aspiration, washing and elution. The method, was validated based upon the MAPA requirements and showed good selectivity, linearity an quantifications limits ranging from 2-10 μg/L. Recovery was satisfactory for all pesticides (71,7-106,9%), intra- and inter-day precision were satisfactory and showed coefficients of variation (CV) less than 16%. Hence, the developed method was applied to the analysis of four real samples of sugarcane juice obtained from different regions.
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Brown, Veronica M. "Development of improved methods for the characterisation of organic chemicals emitted into indoor air by building and furnishing products." Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/8078.
Full textAbstract:
A wide range of organic compounds are released from building and furnishing products and these have the potential to adversely affect indoor air quality. There are growing international requirements for testing and controlling these emissions for the protection of public health. The test methods require specialist analytical chemistry facilities based on thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS). This project has addressed the need for better performance and greater automation of the analysis, as well as development of simpler screening tests. A variety of products were tested using screening techniques, with an emission cell method being used as a reference test. Short duration tests, using a micro-scale chamber at slightly elevated temperature, were shown to have the potential to predict emissions occurring during longer term reference tests. Multi-sorbent air sampling tubes, that have the potential to extend the volatility range of compounds determined by a single TD/GC/MS analysis, were compared with Tenax TA tubes specified by current standard methods. This showed no difference in performance for the range of compounds for which Tenax is optimal, with improved performance for a number of more volatile compounds. The determination of formaldehyde was investigated using 2-hydroxymethylpiperidine as a derivatising agent, followed by TD/GC/MS. The results showed the possibility of this method being developed as an alternative to the current standard method that involves solvent elution and liquid chromatography. The performance of a newly developed time-of-flight mass spectrometer was compared with a standard quadrupole instrument. This showed its potential, with the use of re-collection, to extend the concentration range of compounds quantified from a single air sample, of particular benefit for the determination of carcinogens. New compound identification software was applied to increase automation of analysis of the TD/GC/MS data. Good correlation with manual processing was achieved, demonstrating the possibility of routine application to material emissions testing.
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Aarseth, Larsson Kim. "Chemical Characterisation of Nitrocellulose." Thesis, Örebro universitet, Institutionen för naturvetenskap och teknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-41416.
Full textAbstract:
Nitrocellulose is the main component in many types of ammunition, propellants and explosives. The principles of production for nitrocellulose have not changed much since the 19th century when it started being industrially produced for this purpose. The character of the nitrocellulose has a large effect on the end products abilities. The aim of this study was to develop a method that would be able to characterise and distinguish between nitrocellulose from different manufacturers to be able to relate the character of the nitrocellulose to the properties of ammunition, propellants and explosives. Samples were dissolved in acetone and analysed by GC/MS and data were then analysed by multivariable statistics. FTIR was also used to characterise the nitrocellulose. Results from both methods showed very small differences when chromatograms and spectra were analysed. This study shows that GC/MS and FTIR are not suitable for this type of characterisation. The differences between the data were not sufficient to be able to separate the samples from each other.Nitrocellulosa är den viktigaste komponenten i många typer av ammunition, drivmedel och sprängämnen. Principerna för produktionen av nitrocellulosa har inte förändrats mycket sedan det börjades produceras industriellt för detta ändamål på 1800 talet. Karaktären av nitrocellulosa har en stor inverkan på slutproduktens egenskaper. Syftet med denna studie var att utveckla en metod som skulle kunna karaktärisera och skilja mellan nitrocellulosa från olika tillverkare för att kunna relatera karaktären av nitrocellulosa till egenskaperna hos ammunition, drivmedel och sprängämnen. Proverna löstes i aceton och analyserades med GC/MS och data analyserades med multivariabel statistik. FTIR användes också för att karakterisera nitrocellulosan. Resultaten för båda proverna visade mycket små skillnader när kromatogram och spektra analyserades. Denna studie visar att GC/MS och FTIR inte är lämpliga för denna typ av karaktärisering. Skillnaderna i data var inte tillräckliga för att kunna skilja proverna från varandra.
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Santos, Marcelo Filonzi dos. "Redistribuição postmortem de antidepressivos e seus produtos de biotransformação em tecidos biológicos humanos." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/9/9141/tde-09022015-092617/.
Full textAbstract:
Os antidepressivos pertencem a uma importante classe de medicamentos investigados na toxicologia forense. Em casos de amostras provenientes de cadáveres, o intervalo entre o óbito e a obtenção da espécie biológica pode proporcionar a redistribuição postmortem destes fármacos. Com o objetivo de elucidar esse fenômeno, métodos analíticos foram desenvolvidos e aplicados utilizando sangue total (ST), humor vítreo (HV) e fígado. Para as amostras de ST e HV, o método de extração escolhido e validado foi a microextração em fase líquida (LPME) trifásica. Fibras ocas constituídas de polipropileno, com a extensão de 8 cm cada, foram tratadas com o solvente orgânico dodecano (fase orgânica), resultando em um membrana com permeabilidade seletiva. No lúmen destas fibras, adicionou-se ácido fórmico 0,1 mol/L (fase aceptora). Em frasco de fundo chato com 5 mL de capacidade, pipetou-se 3,5 mL de NaOH 0,1 mol/L (fase doadora) e 0,5 mL de ST ou HV. Ao término da extração, as amostras foram introduzidas no GC-MS, sem a necessidade de reações de derivatização. O estudo com ST contemplou os antidepressivos amitriptilina (AMI), nortriptilina (NTR), imipramina (IMI), desipramine (DES), clomipramina (CLO), desmetilclomipramina (DMC), fluoxetina (FLU) e norfluoxetina (NFL). Os limites de quantificação para estas substâncias ficaram inferiores aos níveis terapêuticos (20 ng/mL). As médias dos coeficientes de variação intradia e interdia foram, respectivamente, de 9,7 e 9,8%. As curvas de calibração apresentaram linearidade entre as concentrações de 20 até 1200 ng/mL. A validação do parâmetro integridade da diluição assegurou a mensuração de quantidades superiores ao limite apresentado na curva de calibração. O método foi aplicado em sete amostras reais postmortem e em apenas um caso foi observada uma diferença significativa (300%) entre os valores quantificados no ST periférico e central. Os antidepressivos tricíclicos AMI, NTR, IMI e DES foram avaliados no HV e o efeito matriz foi detectado para os dois últimos analitos. O método foi otimizado e validado utilizando solução salina adicionada de AMI e NTR. O limite de detecção igual a 5 ng/mL, foi obtido com a redução da voltagem da fonte de íons do espectrômetro de massa para 50 eV. Coeficientes de variação foram inferiores a 15%. Os procedimentos validados foram aplicados em seis amostras reais de HV. A relação encontrada entre os valores obtidos no ST periférico e HV foi de aproximadamente 0,1. A extração acelerada por solvente (ASE) e, posteriormente, a extração em fase sólida (SPE) foram as técnicas de separação dos analitos da matriz fígado. Ao término das citadas extrações, os antidepressivos foram analisados no GC-MS. Para esta matriz sólida, são necessários mais estudos, pois os valores encontrados nos ensaios analíticos estão em desacordo com as diretrizes utilizadas na validação dos métodos.Antidepressants belong to an important class of drugs investigated in forensic toxicology. In cases of samples from corpses, the interval between death and obtaining the biological specimens can provide the postmortem redistribution of these drugs. Aiming to elucidate this phenomenon, analytical methods were developed and applied using whole blood (WB), vitreous humor (VH) and liver. For samples of WB and HV, the extraction method chosen and validated was the three-phase liquid phase microextraction (LPME). Hollow fibers consist of polypropylene, with a length of 8 cm each were treated with dodecane organic solvent (organic phase) resulting in a membrane with selective permeability. Into the lumen of these fibers was added formic acid 0.1 mol/ L (acceptor phase). In the vial containing 3.5 mL of NaOH 0.1 mol / L (donor phase) was spiked 0.5 ml of biological fluids (WB or VH). Subsequently, the samples were injected in GC-MS without derivatization reactions. The study of the ST included antidepressants amitriptyline (AMI), nortriptyline (NTR), imipramine (IMI), desipramine (DES), clomipramine (CLO), desmethylclomipramine (DMC), fluoxetine (FLU) and norfluoxetine (NFL). The quantification limits for these substances were below the therapeutic levels (20 ng / ml). The mean coefficients of variation and separate intradays were respectively 9.7 and 9.8%. The calibration curves showed linearity between concentrations of 20 to 1200 ng / mL. The validation of the integrity of the dilution parameter assured measurement higher than the limit shown in the calibration curve quantities. The method was applied to seven real postmortem samples and in one case a significant difference (300%) between the measured values in the peripheral and central ST was observed. The tricyclic antidepressants AMI, NTR, IMI and DES were evaluated in VH and the matrix effect was detected in the last two analytes. The method was optimized and validated using saline spiked AMI and NTR. The limit of detection (5 ng/ml) was obtained by reducing the voltage of the ion source of the mass spectrometer 50 eV. Coefficients of variation were below 15%. The procedures were validated in six real samples of HV. The relationship found between the values obtained in the peripheral ST and HV was approximately 0.1. Accelerated solvent extraction (ASE) and subsequently the solid phase extraction (SPE) were the techniques of separation of analytes liver matrix. At the end of the cited extractions, antidepressants were analyzed in GC-MS. To this solid tissue, further studies are needed, because the values found in the analytical tests were not in accordance with the guidelines used in the validation of the methods.
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Colasso, Camilla Gomes. "Avaliação da exposição ocupacional a praguicidas organofosforados em estufas de flores na região do Alto Tietê - São Paulo." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/9/9141/tde-20122011-084705/.
Full textAbstract:
O estado de São Paulo é responsável por 70% da produção nacional de flores e plantas ornamentais. Esses cultivos ocupam 7,5 mil hectares e mais da metade desta área é cultivada em estufas. Atualmente existem aproximadamente 8 mil produtores de pequeno, médio e grande porte em todo Brasil e este setor gera em torno de 200 mil empregos diretos, abrangendo produção e comércio. As estufas são microcosmos planejados para propiciar as condições ambientais adequadas ao crescimento de plantas. Qualquer infestação é controlada usando praguicidas que, devido ao enclausuramento e ajustes das condições climáticas, podem prolongar e intensificar a exposição ocupacional aos mesmos. Alguns estudos sugerem que os trabalhadores de estufas de flores e plantas ornamentais estão expostos a níveis mais elevados de praguicidas durante o carregamento, mistura e aplicação dos praguicidas, bem como pelo contato contínuo com as flores e plantas ornamentais, quando comparados a outros trabalhadores que entram em contato com essa classe de compostos. No presente trabalho, objetivou-se conhecer o processo de trabalho, práticas de saúde, higiene e segurança e localizar possíveis fontes de exposição ocupacional a praguicidas nas estufas de flores da região do Alto Tietê, e também otimizar métodos analíticos para a detecção e quantificação de praguicidas organofosforados (diclorvós, metil-paration e metidation) em patches de algodão e em tubos coletores XAD-2, com o intuito de analisar a exposição ocupacional dérmica e inalatória. O processo de avaliação incluiu o acompanhamento da jornada de trabalho, entrevistas e aplicação de questionários de trabalhadores de 18 estufas. Destas 18 foram selecionadas 6 estufas para coleta de amostras. Os organofosforados diclorvós, metidation e metilparation foram detectados e quantificados por cromatografia gasosa/espectrometria de massas (GC-MS), operado no modo de ionização por impacto de elétrons. Os dados da avaliação qualitativa demonstraram percentual elevado de desconhecimento das práticas adequadas de saúde, higiene e segurança para a utilização destes compostos, sugerindo que há risco de exposição durante a manipulação, armazenamento e descarte dos mesmos. Os limites de quantificação (LQ) obtidos foram abaixo de 0,4 ng/mL e limites de detecção (LD) foram abaixo de 0,1 ng/mL para todos os compostos. O método mostrou boa linearidade na concentração estudada (LSQ-500 ng/mL), com coeficiente (r) maior que 0,99. A precisão foi avaliada pelo desvio padrão relativo e apresentou valores inferiores a 15% para todos os compostos estudados. Após os métodos serem validados, foi realizada a amostragem dérmica e do ar e encontraram-se concentrações variadas de praguicidas.The state of São Paulo - Brazil, accounts for 70% of domestic production of flowers and ornamental plants. Currently, these crops occupy 7.5 thousand hectares and over 50% of this area is cultivated in greenhouses. This market has an average of 8.000 producers and generates around 200.000 jobs. Greenhouses are microcosms designed to provide environmental conditions suitable for plant growth. Infestation is controlled using pesticides that due to the closure and adjustment to the weather conditions can prolong and intensify the exposure to them. Some studies suggest that workers in greenhouses of flowers and ornamental plants are exposed to higher levels of pesticides during loading, dilution and application, as well as by continuous contact with flowers and ornamental plants, when compared to other workers who enter in contact with this class of compounds. The aim of the present was to know the work process, to survey the practices of health, hygiene and safety standards and locate possible sources of occupational exposure to pesticides in greenhouses of flowers in the Alto Tietê region (São Paulo state), and to optimize analytical methods for detection and quantification of organophosphate pesticides (dichlorvos, methyl parathion and methidathion) in patches of cotton and in XAD-2 sorbent tubes, with the aim of analyzing the occupational dermal and inhalation exposure. The evaluation process included the monitoring of the working day, interviews and questionnaires, and samples collected in greenhouses. The organophosphorus compounds were detected and quantified by gas chromatography/mass spectrometry (GC-MS) operated in electron impact ionization. The data show a high percentage of lack of appropriate health practices, hygiene and safety for pesticide use suggests that there is risk of exposure during handling, storage and disposal of them. The limits of quantification (LOQ) obtained were below 0.4 ng/mL and limits of detection (LOD) were below 0.1 ng/mL for all compounds. The method showed good linearity in the studied concentration (LOQ-500 ng/mL), with coefficient (r) greater than 0.99. The precision was evaluated by relative standard deviation and showed values below 15% for all compounds studied. After the methods are validated, the dermal and air sampling was performed and a great range of pesticide concentrations was found. So it is evident that this study is valuable for future analysis and guidance to workers about possible hazards and proper use for reducing exposure to these compounds.
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Burman, Lina. "Chromatography and extraction techniques for new evaluation methods of polyolefins long-term performance." Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-219.
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Paris, Alice. "Extractions et analyses des hydrocarbures aromatiques : approches méthodologiques et applications à des matrices fruitières." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMC246/document.
Full textAbstract:
Les hydrocarbures aromatiques monocycliques (BTEX) et polycycliques (HAP) sont pour la plupart reconnus pour leur toxicité via ingestion. Le suivi de leur contenu dans les matrices alimentaires est donc indispensable. Plusieurs approches sensibles et complémentaires ont été établies, avec la pomme comme modèle d’étude, pour la double détermination de ces hydrocarbures aromatiques volatils et semi-volatils au niveau du µg/kg.Une micro-extraction en phase solide dans l’espace de tête (HS-SPME) a été utilisée pour l'extraction des hydrocarbures aromatiques les plus légers (MM entre 78 et 178 g/mol). La récupération des composés les plus lourds (MM entre 202 et 278 g/mol) a quant à elle été permise par une méthodologie basée sur l'extraction assistée par les ultrasons (UAE) suivie d'une extraction en phase solide (SPE). Une alternative plus sensible à cette stratégie combinant l’HS-SPME et l’UAE/SPE pour la détermination globale des hydrocarbures aromatiques a également été développée. Le remplacement de l’étape de SPE par une micro-extraction sur solide compacté (MEPS) a permis une récupération plus rapide, sensible et plus large des HAP (MM entre 152 et 278 g/mol).L’ensemble des stratégies d'extraction, associées à des analyses en chromatographie gazeuse couplée à la spectrométrie de masse, a ensuite pu être appliqué à la détermination des 20 composés aromatiques ciblés dans des pommes récoltées en Normandie ou des fruits provenant du commerce contaminés ou non par des gaz d’échappement ou des fumées de combustion de biomasse. Ces applications ont révélé la faible contamination des pommes normandes étudiées, l’adsorption prédominante des composés aromatiques au niveau de la peau des fruits et leur faible transfert vers la chairMonocyclic aromatic hydrocarbons (BTEX) and polycyclic aromatic hydrocarbons (PAHs) are considered and recognized as toxic compounds via ingestion. Their monitoring in food product is thus a significant concern. Sensitive and complementary experimental approaches were investigated with apple as model for the dual determination of volatile and semi-volatile aromatic hydrocarbons at the ppb level.A solid-phase micro-extraction in the headspace of samples (HS-SPME) was used for the most volatile aromatic hydrocarbons (MW between 78 and 178 g/mol). The recovery of the least volatile aromatic hydrocarbons (MW between 202 and 278 g/mol) was implemented with an ultrasound assisted extraction (UAE) followed by a purification step using a solid phase extraction (SPE). The methodology consisting in HS-SPME and UAE/SPE enabled the global determination of BTEX and PAHs. The SPE step was then substituted by a micro-extraction with a packed sorbent (MEPS) to elaborate a most sensitive and rapid methodology for the quantification of a wider range of PAHs (MW between 152 and 278 g/mol).Extraction procedures associated with analyses using gas chromatography and mass spectrometry were then applied to the determination of 20 targeted aromatic compounds in apples harvested in Normandy or in commercial fruits exposed or not exposed to exhaust gas or to wood smoke. These applications revealed low levels of contaminants in the studied apples from Normandy. A predominant adsorption of aromatic compounds occurs on the skin of fruits and the transfer to the pulp is almost inexistent