Página 1 dos resultados de 69 itens digitais encontrados em 0.014 segundos
- Universidade Federal do Rio Grande do Sul
- Biblioteca Digital da Unicamp
- Elsevier
- Universidade de Aveiro
- Universidade do Algarve
- Sociedade Brasileira de Química
- Association of Biomolecular Resource Facilities
- The Mass Spectrometry Society of Japan
- Public Library of Science
- Universidade da Madeira
- American Chemical Society
- Universidade de Cambridge
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Obtenção de bio-óleos por pirólise de resíduos da indústria de celulose e sua caracterização por cromatografia gasosa
Fonte: Universidade Federal do Rio Grande do Sul
Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Tese de Doutorado
Formato: application/pdf
POR
Relevância na Pesquisa
37.12%
A indústria de celulose do Brasil progrediu muito nas últimas décadas no que tange ao gerenciamento ambiental de seus resíduos. Entretanto, existem perspectivas para usos mais nobres destes resíduos, objetivando-se um gerenciamento ambiental ainda melhor e, eventualmente, economicamente vantajoso. Neste trabalho, a serragem, o resíduo do digestor e o lodo da ETE foram submetidos a condições de pirólise. O processo de pirólise foi desenvolvido para o resíduo do digestor, e após, foi aplicado para as demais biomassas, a fim de avaliar o potencial de todos os resíduos para a produção de bio-óleos. As cromatografias gasosas monodimensional (1D-GC/qMS) e bidimensional abrangente (GC×GC/TOFMS) foram utilizadas para análise qualitativa e semiquantitativa dos bio-óleos. A maior eficiência da GC×GC/TOFMS proporcionou um estudo detalhado da composição dos bio-óleos, indicando a presença de um maior número de compostos detectados e tentativamente identificados e de coeluições que ocorreram na 1D-GC/qMS, aprimorando a investigação de caracterização dos bio-óleos. Por outro lado, a 1D-GC implica em uma análise mais simples e de menor custo, que forneceu uma visão geral dos componentes majoritários dos bio-óleos. Produtos de importância industrial...
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Microextração em fase sólida e cromatografia gasosa convencional e bidimensional para classificação de méis; Solid phase microextraction and conventional and comprehensive gas chromatography for the classification of honeys
Fonte: Biblioteca Digital da Unicamp
Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado
Formato: application/pdf
Publicado em 17/11/2011
PT
Relevância na Pesquisa
36.61%
#Cromatografia gasosa#Mel#Microextração em fase sólida#Cromatografia#Gas chromatography#Honey#Solid phase microextraction#Comprehensive chromatography
A técnica de microextração em fase sólida através do headspace (HS-SPME) combinada com a cromatografia gasosa bidimensional abrangente e detecção por ionização em chama (GCxGCxFID) foi empregada para detectar artefatos formados durante o preparo da amostra de méis, que poderiam ser prejudiciais ao processo de identificação de sua origem floral. O método foi otimizado utilizando-se planejamento multivariado. Para isso, uma mistura de diferentes tipos de méis brasileiros foi usada como modelo. Os artefatos de extração identificados foram classificados como resultantes da manipulação através do HS. A influência da temperatura e do tempo de exposição ao tratamento térmico também foi avaliada. A identificação da fração volátil da mistura de mel foi realizada por GCxGCxFID e cromatografia gasosa acoplada à espectrometria de massas com analisador quadrupolar (GC-QMS) comparando-se o índice de retenção linear com programação de temperatura obtido na primeira dimensão (D-LTPRI), calculado a partir dos cromatogramas obtidos por GCxGCxFID, e os índices obtidos por GC-QMS para as mesmas amostras. Esta identificação foi confirmada por cromatografia gasosa bidimensional abrangente combinada a um espectrômetro de massas por tempo de vôo (GCxGCxTOFMS). Portanto...
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Deeper insight into the monoterpenic composition of Ferula gummosa oleo-gum-resin from Iran
Fonte: Elsevier
Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
47.03%
#Ferula gummosa Boiss#Oleo-gum-resin#Essential oil#Monoterpenic composition#Comprehensive two-dimensional gas chromatography (GC × GC–ToFMS)
The monoterpenic composition of the essential oil of oleo-gum-resin Ferula gummosa Boiss from Iran was studied by GC x GC-ToFMS. This study allowed to tentatively identify 130 monoterpenic compounds including 24 hydrocarbons, 52 alcohols, 4 ethers, 20 aldehydes, 8 oxides, 18 ketones, 1 furan and 3 epoxides, from which only 25 were reported before in this species. Furthermore, while previous studies identified terpenic hydrocarbons such as beta- and alpha-pinene as the most abundant monoterpenes, in the present study monoterpene alcohols as myrtenol, mentha-1,8-dien-7-ol, two pinocarveol isomers and mentha-1,5-dien-8-ol were the predominant components. GC x GC-ToFMS analysis allowed achieving a deeper characterization of the monoterpenic composition of F. gurnmosa, which may contribute to the increase of the value of this biomass plant material as a source of monoterpenic compounds. Moreover, this approach allows a more efficient quality control for existent applications and to prevent adulterations, promoting market confidence. (C) 2011 Elsevier B.V. All rights reserved.
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Red deer gender and populations analysis using scats’ volatile profile; Perfil volátil de excrementos de veado
Fonte: Universidade de Aveiro
Publicador: Universidade de Aveiro
Tipo: Dissertação de Mestrado
ENG
Relevância na Pesquisa
36.82%
#Gestão de ecossistemas#Veados#População animal#Cervus elaphus#Chemical communication#Diet#Gender distinction#Genetic background#Populations#Scats#Volatile compounds
Current populations of red deer (Cervus elaphus) in Portugal derive from recent reintroduction processes and natural dispersion movements from Spain. These movements promote the expansion of the species and reproduction among different populations, increasing the need for more sophisticated methodologies
able to differentiate populations and determine sex-ratio, two demographic parameters used in the management of populations. Headspace solid phase microextraction and comprehensive two-dimensional chromatography coupled to mass spectrometry for time of flight gas phase mode (HS-SPME/GC×GC–
ToFMS) arises as a possible solution to the determination of these parameters. Thus, this work aims to test for differences between red deer populations, using scats from natural fenced red deer populations as a model to distinguish between sexes. The obtained volatiles are an attempt to determine specific
sets of compounds or chemical families’ markers for males, females and for each population, targeting the use in wildlife approaches. In fact, results showed that populations and gender successful differentiation was based on a sub-set of probably, diet and chemical communication compounds, respectively. The mechanism underling this differentiation is probably the interaction of genetics and environment leading to changes in animals’ physiology...
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Optimization and validation of a method for the analysis of target compounds migrating from organic materials used in contact with water intended for human consumption by SPME-GC-TOFMS
Fonte: Universidade do Algarve
Publicador: Universidade do Algarve
Tipo: Dissertação de Mestrado
Publicado em //2012
ENG
Relevância na Pesquisa
36.68%
Dissertação de mest., Qualidade em Análises, Faculdade de Ciências e Tecnologia, Univ. do Algarve, 2012; The leaching of toxic organic substances from polymeric materials in distribution systems into drinking water intended for human consumption has led to an urgent need for the continuous development of new analytical methods for their monitoring and evaluation so that high consumer confidence could be established.
An analytical method is developed and validated based on the combination of SPME and GC/TOFMS for the determination of seven target compounds: n-butylacetate, m-xylene, p-xylene, 1,3-dichloroacetone, styrene, o-xylene, cyclohexanone. The chromatographic conditions are optimized so that the analysis is performed in the shortest possible time and a specific mass ion for each compound is targeted in the TOF mass spectrum for quantification.
Three SPME adsorption parameters: mode of extraction, extraction temperature and time are optimized for five fibers to attain the best selectivity and sensitivity for each target compound and based on the highest extraction efficiency, the best fiber and its optimized conditions are used for the validation process.
The LOD and LOQ were lower than the lowest concentrations used in the calibration curves and the determination coefficient (r2) ranged from 0.995-0.999 within the tested working ranges for all target compounds. The coefficient of variation for repeatability studies was less than 25% for all compounds but it exceeded 25% for some compounds during intermediate precision studies. Recovery studies in both tap and surface water showed that matrix effects play a significant role in the extraction of target compounds from water.
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Comprehensive two-dimensional gas chromatography with time of flight mass spectrometry applied to analysis of Fischer-Tropsch synthesis products obtained with and without carbon dioxide addition to feed gas
Fonte: Sociedade Brasileira de Química
Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica
Formato: text/html
Publicado em 01/11/2011
EN
Relevância na Pesquisa
36.92%
Comprehensive two-dimensional gas chromatography coupled to time of flight mass spectrometry (GC × GC-TOFMS) was applied to evaluate the CO2 effect on distribution of n-alkanes, branched alkanes, alkenes and oxygen-containing compounds in Fischer-Tropsch products. GC × GC-TOFMS was able to resolve the unresolved compounds observed in conventional GC.
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Photochemical degradation of diesel oil in water: a comparative study of different photochemical oxidation processes and their degradation by-products
Fonte: Sociedade Brasileira de Química
Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica
Formato: text/html
Publicado em 01/08/2014
EN
Relevância na Pesquisa
36.53%
This paper provides a comparative study of different photochemical oxidation processes and a detailed characterization of the by-products of diesel oil degradation performed using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOFMS). Diesel degradation was conducted in a photolytic reactor using UV, H2O2, UV/H2O2, O3 or O3/UV. The best conditions for each process were obtained applying multivariate analysis and the experimental results indicated that the O3/UV process was the most feasible for the treatment of wastewater containing diesel fuel, with a degradation percentage of > 90%. Almost complete degradation of the aromatics was achieved. Phenolic compounds were identified as by-products of the diesel samples treated with the UV, H2O2, O3 and O3/UV processes. Besides the phenolic compounds, other by-products identified included carboxylic acids and ethers in the UV/peroxide treatment, ethers in the UV irradiation treatment and ketones in the ozone treatment.
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Application of Comprehensive Two-Dimensional Gas Chromatography with Time-of-Flight Mass Spectrometry Method to Identify Potential Biomarkers of Perinatal Asphyxia in a Non-human Primate Model
Fonte: PubMed
Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36.82%
Perinatal asphyxia is a leading cause of brain injury in infants, occurring in 2–4 per 1000 live births. The clinical response to asphyxia is variable and difficult to predict with current diagnostic tests. Reliable biomarkers are needed to help predict the timing and severity of asphyxia, as well as response to treatment. Two-dimensional gas chromatography-time-of-flight-mass spectrometry (GC x GC-TOFMS) was used herein, in conjunction with chemometric data analysis approaches for metabolomic analysis in order to identify significant metabolites affected by birth asphyxia. Blood was drawn before and after 15 or 18 minutes of cord occlusion in a Macaca nemestrina model of perinatal asphyxia. Postnatal samples were drawn at 5 minutes of age (n=20 subjects). Metabolomic profiles of asphyxiated animals were compared to four controls delivered at comparable gestational age. Fifty metabolites with the greatest change pre- to post-asphyxia were identified and quantified. The metabolic profile of post-asphyxia samples showed marked variability compared to the pre-asphyxia samples. Fifteen of the 50 metabolites showed significant elevation in response to asphyxia, ten of which remained significant upon comparison to the control animals. This metabolomic analysis confirmed lactate and creatinine as markers of asphyxia and discovered new metabolites including succinic acid and malate (intermediates in the Krebs cycle) and arachidonic acid (a brain fatty acid and inflammatory marker) as potential biomarkers. GC × GC-TOFMS coupled with chemometric data analysis are useful tools to identify acute biomarkers of brain injury. Further study is needed to correlate these metabolites with severity of disease...
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Metabolic Profiling of a Corynebacterium Glutamicum DeltaprpD2 by GC-APCI High Resolution Q-TOF Analysis
Fonte: Association of Biomolecular Resource Facilities
Publicador: Association of Biomolecular Resource Facilities
Tipo: Artigo de Revista Científica
Publicado em /10/2011
EN
Relevância na Pesquisa
36.47%
Metabolomics studies based on Gas chromatography–Mass spectrometry (GC-MS) are well established and typically employ electron impact (EI) ionisation. Target compounds of interest can be identified by comparison to commercial or public databases. Unfortunately, many possible biomarkers detected in metabolic profiling experiments cannot be identified due to the lack of reference spectra for a majority of biologically relevant compounds. Therefore, many possible biomarkers remain “unknowns” up till now. Hyphenating gas chromatography with high resolution TOF-MS technology with soft atmospheric pressure ionisation (APCI) can preserve the molecular ion information and delivers accurate mass and isotopic pattern information. This data enables a sum formula generation for known and unknown target compounds. Additionally, optionally acquired MS/ MS data can extend the capabilities for structural elucidation. Mass accuracy, resolution and isotopic fidelity are independent of the TOFMS acquisition rate. Therefore, these instruments can be coupled to gas chromatography, which typically delivers narrow peak width requiring fast MS scan speeds. Corynebactrium glutamicum, a gram positive, nontoxic bacterium, is used in the industrial production of amino acids like lysine and glutamate. C. glutamicum can be grown on different carbon sources. Glucose is metabolised via glycolysis and the tricarboxylic acid (TCA) cycle...
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Comprehensive Two Dimensional Gas Chromatography Fast Quadrupole Mass Spectrometry (GC×GC-qMS) for Urinary Steroid Profiling. Mass Spectral Characteristics with Chemical Ionization
Fonte: PubMed
Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36.68%
Comprehensive two dimensional GC (GC×GC), coupled to either a time of flight MS (TOF-MS) or a fast scanning quadrupole MS (qMS) has greatly increased the peak capacity and separation space compared to conventional GC-MS. However, commercial GC×GC-TOFMS systems are not equipped with chemical ionization (CI) and do not provide dominant molecular ions or enable single ion monitoring for maximal sensitivity. A GC×GC-qMS in mass scanning mode was investigated with EI and positive CI (PCI), using CH4 and NH3 as reagent gases. Compared to EI, PCI-NH3 produced more abundant molecular ions and high mass structure specific ions for steroid acetates. Chromatography in two dimensions was optimized with a mixture of 12 endogenous and 3 standard acetylated steroids (SM15-AC) relevant to doping control. Eleven endogenous target steroid acetates were identified in normal urine based on their two retention times, and EI and PCI-NH3 mass spectra; nine of these endogenous target steroid acetates were identified in congenital adrenal hyperplasia (CAH) patients. The difference between the urinary steroids profiles of normal individuals and from a CAH patient can easily be visually distinguished by their GC×GC-qMS chromatograms. We focus here on the comparison and interpretation of the various mass spectra of the targeted endogenous steroids. PCI-NH3 mass spectra were most useful for unambiguous molecular weight determination and for establishing the number of -OH by the losses of 1 or more acetate groups. We conclude that PCI-NH3 with GC×GC-qMS provides improved peak capacity and pseudomolecular ions with structural specificity.
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Powerful GC-TOF-MS Techniques for Screening, Identification and Quantification of Halogenated Natural Products
Fonte: The Mass Spectrometry Society of Japan
Publicador: The Mass Spectrometry Society of Japan
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36.61%
Comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC×GC TOFMS) and gas chromatography/high-resolution time-of-flight mass spectrometry (GC-HRT) were used to detect and identify halogenated natural products (HNPs) in tissue homogenate, in this case brominated analytes present in a marine snail. Two classes of brominated anthropogenic compounds, polybrominated diphenyl ethers (PBDEs) and brominated dibenzofurans, were analyzed for comparison. Following conventional preparation, the sample was analyzed using GC×GC-TOF-MS. Isotope ratio scripts were used to compile a list of putatively brominated analytes from amongst the thousands of features resolved in the two-dimensional chromatogram. The structured nature of the chromatogram was exploited to propose identifications for several classes of brominated compounds, and include additional candidates that fell marginally outside the script tolerances. The sample was subsequently analyzed by GC-HRT. The high-resolution mass spectral data confirmed many formula assignments, facilitated confident assignment of an alternate formula when an original proposal did not hold, and enabled unknown identification. Identified HNPs include hydroxylated and methoxylated PBDE analogs...
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GC-MS Based Plasma Metabolomics for Identification of Candidate Biomarkers for Hepatocellular Carcinoma in Egyptian Cohort
Fonte: Public Library of Science
Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 01/06/2015
EN
Relevância na Pesquisa
36.63%
This study evaluates changes in metabolite levels in hepatocellular carcinoma (HCC) cases vs. patients with liver cirrhosis by analysis of human blood plasma using gas chromatography coupled with mass spectrometry (GC-MS). Untargeted metabolomic analysis of plasma samples from participants recruited in Egypt was performed using two GC-MS platforms: a GC coupled to single quadruple mass spectrometer (GC-qMS) and a GC coupled to a time-of-flight mass spectrometer (GC-TOFMS). Analytes that showed statistically significant changes in ion intensities were selected using ANOVA models. These analytes and other candidates selected from related studies were further evaluated by targeted analysis in plasma samples from the same participants as in the untargeted metabolomic analysis. The targeted analysis was performed using the GC-qMS in selected ion monitoring (SIM) mode. The method confirmed significant changes in the levels of glutamic acid, citric acid, lactic acid, valine, isoleucine, leucine, alpha tocopherol, cholesterol, and sorbose in HCC cases vs. patients with liver cirrhosis. Specifically, our findings indicate up-regulation of metabolites involved in branched-chain amino acid (BCAA) metabolism. Although BCAAs are increasingly used as a treatment for cancer cachexia...
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Preliminary Investigation of Medicinal Herb Adulteration Using Comprehensive Two-Dimensional Gas Chromatography and Chemometric Analysis
Fonte: Sociedade Brasileira de Química
Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica
Formato: text/html
Publicado em 01/06/2015
EN
Relevância na Pesquisa
46.88%
Anise is frequently found among the ingredients described in the label of cosmetic products. However, the use of fennel instead of anise may occur due to the lower price of fennel. The main differences in volatile profile of anise and fennel fruits were, for the first time, evaluated using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometric detection (GC×GC/TOFMS) and chemometric analysis. Aproximately 950 peaks were found in chromatograms of each sample and Fisher ratio appointed 31 volatile analytes as the most discriminating between anise and fennel samples. These 31 compounds were used in principal component analysis and canonical discriminant analysis that designated seven compounds (estragole, methyl eugenol, 4,5-dehydro-isolongifolene, calamenene, linalool, β-ocimene and fenchol) as the most important to verify the use of fennel or anise in personal care products. Among these seven compounds, thrree coeluted with other compounds and were correctly identified only with the use of GC×GC/TOFMS.
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Non-invasive strategy in assessing asthma through biofluids metabolomics exploration: exhaled breath and urine potentialities
Fonte: Universidade da Madeira
Publicador: Universidade da Madeira
Tipo: Tese de Doutorado
Publicado em /11/2014
ENG
Relevância na Pesquisa
36.97%
#Asthma#Exhaled breath#Urine#Metabolomics#GCxGC-ToFMS#1H NMR#Chemistry, specialty in Analytical Chemistry#.#Centro de Ciências Exatas e da Engenharia
Asthma is a significant health issue in the pediatric population with a noteworthy growth over the years. The proposed challenge for this PhD thesis was the development of advanced methodologies to establish metabolomic patterns in urine and exhaled breath associated with asthma whose applicability was subsequently exploited to evaluate the disease state, the therapy adhesion and effect and for diagnostic purposes. The volatile composition of exhaled breath was studied combining headspace solid phase microextraction (HS-SPME) with gas chromatography coupled to mass spectrometry or with comprehensive two-dimensional gas chromatography coupled to mass spectrometry with a high resolution time of flight analyzer (GC×GC–ToFMS). These methodologies allowed the identification of several hundred compounds from different chemical families. Multivariate analysis (MVA) led to the conclusion that the metabolomic profile of asthma individuals is characterized by higher levels of compounds associated with lipid peroxidation, possibly linked to oxidative stress and inflammation (alkanes and aldehydes) known to play an important role in asthma. For future applications in clinical settings a set of nine compounds was defined and the clinical applicability was proven in monitoring the disease status and in the evaluation of the effect and / or adherence to therapy. The global volatile metabolome of urine was also explored using an HSSPME/GC×GC–ToFMS method and c.a. 200 compounds were identified. A targeted analysis was performed...
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Volatile exometabolone analysis of Aspergillus niger and search for molecular biomarkers pattern; Análise do exometaboloma volátil de Aspergillus niger e pesquisa de um padrão de biomarcadores moleculares
Fonte: Universidade de Aveiro
Publicador: Universidade de Aveiro
Tipo: Dissertação de Mestrado
ENG
Relevância na Pesquisa
37.03%
#Microbiologia#Fungos patogénicos#Doenças infecciosas#Agentes antifúngicos#Metabolitos#Aspergillus niger#Aspergillus niger#Fungal infections#Volatile exometabolome#HS-SPME/GC×GC–ToFMS#Volatile molecular biomarkers
Fungal infections have greatly increased in risk populations, namely in
immunocompromised patients, probabily because the diagnosis of fungal infections
is delayed. Microbial metabolomics arises as a powerful feature screening the
metabolites produced by microorganisms. It provides information regarding the
state of biological organisms which can be used as a diagnostic tool for diseases
through fungal metabolites pattern. Thus, this research aimed to in-depth study of
the Aspergillus niger exometabolome, in order to establish a targeted metabolomic
pattern that characterizes A. niger. A methodology based on headspace-solid
phase microextraction combined with comprehensive two-dimensional gas
chromatography coupled to mass spectrometry with a high resolution time of flight
analyser (HS-SPME/GC×GC-ToFMS) was used. A. niger exometabolome was
analysed in different growth conditions: temperature (25 and 37 °C), incubation time
(3 and 5 days), and culture medium (solid and liquid medium). A. niger
exometabolome included 430 metabolites, distributed over several chemical
families, being the major ones alcohols, aldehydes, esters, hydrocarbons, ketones
and terpenoids. Differences among volatile metabolites produced under different
growth conditions were observed...
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Estudo sobre metabolitos alvo de Candida albicans com potencial aplicação na sua detecção : impacto das condições de crescimento
Fonte: Universidade de Aveiro
Publicador: Universidade de Aveiro
Tipo: Dissertação de Mestrado
POR
Relevância na Pesquisa
37.03%
#Microbiologia#Fungos patogénicos - Metabolismo#Infecções - Diagnóstico#Agentes antifúngicos#Metabolitos#Candida albicans#Candida albicans, Infeções fúngicas#Infeções fúngicas#Metabolitos#Microextração em fase sólida em modo espaço de cabeça (HS-SPME)#Cromatografia de gás bidimensional abrangente acoplada a espectrometria de massa com analisador por tempo de voo de alta resolução (GC×GC-ToFMS)
Candida albicans é um dos principais fungos patogénicos causadores de infeções fúngicas oportunistas, as quais se manifestam particularmente em indivíduos imunocomprometidos. As infeções fúngicas invasivas estão associadas a uma elevada taxa de mortalidade, devido a um diagnóstico tardio e consequente atraso no início da terapêutica antifúngica. Este trabalho teve como principal objetivo avaliar o impacto das condições de crescimento (tempo e temperatura) no perfil metabolómico global da C. albicans, assim como em alguns metabolitos alvo. A microextração em fase sólida em modo espaço de cabeça combinada com a cromatografia de gás bidimensional abrangente acoplada a espectrometria de massa com analisador por tempo de voo de alta resolução (HS-SPME/GC×GC-ToFMS) foi a metodologia utilizada neste estudo. Foram selecionadas duas temperaturas (25 °C e 37 °C) e quatro tempos de crescimento (6 h, 12 h, 24 h e 48 h). Foi ainda realizado um estudo exploratório com vista a avaliar a aplicabilidade da metodologia desenvolvida de modo a distinguir Candida albicans de outras espécies de Candida não-albicans, Saccharomyces cerevisiae e Aspergillus niger. Este estudo permitiu concluir que a temperatura e o tempo de crescimento influenciaram o metabolismo de Candida albicans...
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Comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry combined with solid phase microextraction as a powerful tool for quantification of ethyl carbamate in fortified wines. The case study of Madeira wine
Fonte: Elsevier
Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em /05/2010
ENG
Relevância na Pesquisa
36.82%
#Ethyl carbamate#Fortified wine#Madeira wine#HS-SPME#GC × GC–ToFMS#.#Faculdade de Ciências Exatas e da Engenharia
An analytical methodology based on headspace solid phase microextraction (HS-SPME) combined with comprehensive two-dimensional gas chromatography—time-of-flight mass spectrometry (GC × GC–ToFMS) was developed for the identification and quantification of the toxic contaminant ethyl carbamate (EC) directly in fortified wines. The method performance was assessed for dry/medium dry and sweet/medium sweet model wines, and for quantification purposes, calibration plots were performed for both matrices using the ion extraction chromatography (IEC) mode (m/z 62). Good linearity was obtained with a regression coefficient (r2) higher than 0.981. A good precision was attained (R.S.D. <20%) and low detection limits (LOD) were achieved for dry (4.31 μg/L) and sweet (2.75 μg/L) model wines. The quantification limits (LOQ) and recovery for dry wines were 14.38 μg/L and 88.6%, whereas for sweet wines were 9.16 μg/L and 99.4%, respectively. The higher performance was attainted with sweet model wine, as increasing of glucose content improves the volatile compound in headspace, and a better linearity, recovery and precision were achieved. The analytical methodology was applied to analyse 20 fortified Madeira wines including different types of wine (dry...
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Prestige Oil spill III, the fate of a heavy oil in the marine environment
Fonte: American Chemical Society
Publicador: American Chemical Society
Tipo: Artículo
Formato: 19968 bytes; application/msword
ENG
Relevância na Pesquisa
36.59%
8 pages, 5 figures.-- PMID: 17539507 [PubMed].-- Printed version published on May 1, 2007.; More than 200 oil samples were collected along the Northern Spanish coast, from December 2002 to December 2003, as part of the extensive monitoring program carried out by the Spanish Marine Safety Agency after the Prestige heavy oil spill (November 13, 2002). The GC FPD/FID and comprehensive GC x GC/TOFMS sample profiles
revealed the main characteristics of the oil residues. Chemical fingerprinting of the aliphatic and aromatic fractions by GC/MS was performed to determine the source of the oil
as well as to follow its weathering at sea. The (n-C13 + n-C14)/(n-C25 + n-C26), n-C18/phytane, and methylnaphthalene [(N + N1)/N2] ratios were found to be useful for assessing the evaporation, biodegradation, and dissolution processes, respectively. Other indicators of more advanced degradation processes, including photo-oxidation, were unaltered, showing the low incidence of natural weathering processes on the spilled heavy oil 1 year after the accident. The survey also demonstrated the occurrence of continued discharges of ballast waters at sea and the need for a more stringent surveillance of the area, beyond accidental oil spills.; This work was supported by the Spanish Ministry of Science and Technology (VEM2003-20068-C05). Samples were made available by SASEMAR (Spain) within its Prestige post-spill monitoring program. The kind support of Laura de la Torre
and Gracia Albuquerque (SASEMAR) is greatly appreciated. The authors thank M. Adahchour and R. J. J. Vreuls for their technical assistance in the GC x GC measurements carried out at the Vrije Universiteit of Amsterdam. S.D. and E.J.
acknowledge the Spanish Ministry of Science and Technology for awarding them a Ramón y Cajal contract and a Ph.D. fellowship...
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Remodeling of central metabolism in invasive breast cancer compared to normal breast tissue - a GC-TOFMS based metabolomics study
Fonte: Universidade de Cambridge
Publicador: Universidade de Cambridge
Tipo: Article; Published Version
EN
Relevância na Pesquisa
36.97%
RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are.; AbstractBackgroundChanges in energy metabolism of the cells are common to many kinds of tumors and are considered a hallmark of cancer. Gas chromatography followed by time-of-flight mass spectrometry (GC-TOFMS) is a well-suited technique to investigate the small molecules in the central metabolic pathways. However, the metabolic changes between invasive carcinoma and normal breast tissues were not investigated in a large cohort of breast cancer samples so far.ResultsA cohort of 271 breast cancer and 98 normal tissue samples was investigated using GC-TOFMS-based metabolomics. A total number of 468 metabolite peaks could be detected; out of these 368 (79%) were significantly changed between cancer and normal tissues (p<0.05 in training and validation set). Furthermore...
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In-depth search focused on furans, lactones, volatile phenols, and acetals as potential age markers of Madeira wines by comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry combined with solid phase microextraction
Fonte: American Chemical Society
Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Publicado em /03/2011
ENG
Relevância na Pesquisa
36.9%
The establishment of potential age markers of Madeira wine is of paramount significance as it may contribute to detect frauds and to ensure the authenticity of wine. Considering the chemical groups of furans, lactones, volatile phenols, and acetals, 103 volatile compounds were tentatively identified; among these, 71 have been reported for the first time in Madeira wines. The chemical groups that could be used as potential age markers were predominantly acetals, namely, diethoxymethane, 1,1-diethoxyethane, 1,1-diethoxy-2-methyl-propane, 1-(1-ethoxyethoxy)-pentane, trans-dioxane and 2-propyl-1,3-dioxolane, and from the other chemical groups, 5-methylfurfural and cis-oak-lactone, independently of the variety and the type of wine. GC × GC-ToFMS system offers a more useful approach to identify these compounds compared to previous studies using GC−qMS, due to the orthogonal systems, that reduce coelution, increase peak capacity and mass selectivity, contributing to the establishment of new potential Madeira wine age markers. Remarkable results were also obtained in terms of compound identification based on the organized structure of the peaks of structurally related compounds in the GC × GC peak apex plots. This information represents a valuable approach for future studies...
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