Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this study, a new modulator that is simple, robust and presents low operation costs was developed. This modulator uses compressed air to cool two small portions of the second chromatographic column of a GC×GC system. To evaluate the modulation process, solutions of alkanes C7 to C29, and pesticides (bifenthrin, cyfluthrin, cypermethrin, esfenvalerate, fenitrotion, fipronil, trifloxystrobin and trifluralin) were analyzed by GC×GC-FID. The results showed small variations of the peaks areas, between 0.67 and 2.80% for alkanes and between 0.24 and 5.34% for pesticides. The standard deviation (SD) for the retention time in the first column (1tR) was around 0.05 min, for alkanes and pesticides. For retention times in the second column (2tR), the SD was 0.04 s for the majority of the compounds, except for cyfluthrin and permethrin (0.08 s). The linear range was between 0.1 and 5.0 mg L-1 with a coefficient of determination (r2) greater than 0.9945 for pesticides analyzed by GC×GC-FID. The GC×GC system proposed was applied in the determination of pyrethroid pesticides (bifenthrin, cypermethrin, deltamethrin, fenvalerate and esfenvalerate and permethrin cis and trans) in grape samples Italy cultivar spiked at 3 levels (0.02, 0.05 and 0.5 mg kg- 1). Samples were extracted by the mini-Luke modified method (acetone method) and pesticides were quantified by GC×GC-μECD. The parameters evaluated in the validation of the method were: analytical curve, linearity, limit of detection (LOD), limit of quantification (LOQ), precision (in terms of repetitivity and intermediate precision) and accuracy (recovery), as well as the matrix effect on the chromatographic response. All analytical curves showed a linear range between 0.02 and 0.5 mg L-1 with r2 greater than 0.9956 and 0.9994 for the curves prepared in solvent (ethyl acetate) and matrix extract (grape), respectively. From the results obtained by calculation of the matrix effect percentage it can be concluded that the pyrethroid pesticides showed a considerable negative matrix effect. The values of method LOQ were 0.01 to 0.02 mg kg-1 for all pyrethroids. The values of recovery for the 3 spiked levels were between 94.3 and 115.2%, with good precision (RSD<18.4%), demonstrating that the performance of the mini-Luke modified method employed for the extractions is satisfactory. This study also showed that the GC×GC-μECD system using a modulator with a double jet of compressed air has potential for application in the analysis of pyrethroid pesticide residues in grapes, since it supplies low values of LOD and LOQ, and good accuracy in the analytical response. / Neste trabalho foi desenvolvido um novo modulador, simples, robusto e de baixo custo de operação. Este modulador utiliza ar comprimido para resfriar duas pequenas porções da segunda coluna cromatográfica de um sistema GC×GC. Para avaliar o processo de modulação utilizaram-se soluções de alcanos C7 a C29 e pesticidas (bifentrina, ciflutrina, cipermetrina, esfenvalerato, fenitrotiona, fipronil, trifloxistrobina e trifluralina) e análise por GC×GC-FID. Os resultados mostraram pequenas variações das áreas dos picos, entre 0,67 e 2,80% para alcanos e entre 0,24 e 5,34% para pesticidas. O desvio padrão (SD) para o tempo de retenção na primeira coluna (1tR) de alcanos e pesticidas foi em torno de 0,05 min. Para o tempo de retenção na segunda coluna (2tR), o SD foi de 0,04 s para a maioria dos compostos, exceto para ciflutrina e permetrina (0,08 s). A faixa linear situou-se entre 0,1 e 5,0 mg L-1 com coeficiente de determinação (r2) maior que 0,9945 para os pesticidas analisados por GC×GC-FID. O sistema GC×GC proposto foi aplicado na determinação de pesticidas piretróides (bifentrina, cipermetrina, deltametrina, fenvalerato e esfenvalerato, e permetrina cis e trans) em amostras de uva cultivar Itália fortificadas em 3 níveis (0,02; 0,05 e 0,5 mg kg-1). As amostras foram extraídas pelo método de mini-Luke modificado (método da acetona) e os pesticidas quantificados por GC×GC-μECD. Os parâmetros avaliados de validação do método foram: curva analítica, linearidade, limite de detecção (LOD), limite de quantificação (LOQ), precisão (em termos de repetitividade e precisão intermediária) e exatidão (recuperação), bem como o efeito matriz na resposta cromatográfica. Todas as curvas analíticas apresentaram faixa linear entre 0,02 e 0,5 mg L-1 com valores de r2 maiores que 0,9956 e 0,9994 para as curvas preparadas em solvente (acetato de etila) e extrato da matriz (uva), respectivamente. A partir dos resultados obtidos através do cálculo do efeito matriz percentual concluiu-se que os pesticidas piretróides avaliados apresentaram considerável efeito matriz negativo. Os valores de LOQ do método foram de 0,01 a 0,02 mg kg-1 para todos os piretróides. A recuperação para os 3 níveis de fortificação ficou entre 94,3 e 115,2%, com boa precisão (RSD<18,4%), o que mostrou que o desempenho do método mini-Luke modificado empregado para as extrações é satisfatório. Este estudo mostrou também, que o sistema GC×GC-μECD com modulador de duplo jato de ar comprimido tem potencial para aplicação nas análises de resíduos de pesticidas piretróides em uva, uma vez que fornece baixos valores de LOD e LOQ, e boa precisão da resposta analítica.

The biggest limitation to conventional gas chromatography (GC) is limited peak capacity, making the analysis of complex mixtures a difficult or even impossible task. Comprehensive two-dimensional gas chromatography (GC×GC) significantly increases peak capacity and resolution, improves sensitivity and generates structured 3D chromatograms. This is achieved by connecting two columns coated with different stationary phases through a special interface (modulator). The interface samples the first column effluent and periodically injects fractions of this material, as narrow injection pulses, onto the second column for further separation. Commercial instruments achieve this with cryogenic agents. Since this expensive approach permits only in-laboratory analysis, the development of simple, economical and field-capable GC×GC systems is in demand. This report summarizes the fundamentals governing GC×GC separations and a brief history of technological advances in the field. It also documents the construction of a simple interface, devoid of moving parts and cryogenic consumables, and hence highly suitable for field analysis and monitoring applications. Evaluation of the interface suggests on-par performance with more complicated cryogenic modulators. GC×GC separations of technical mixtures of fatty acid methyl esters (FAMEs), common environmental pollutants (EPA 8270), polychlorinated biphenyls (PCBs), pesticides (toxaphene), as well as selected essential oils and major distillation fractions of crude oil indicate very good performance. Most notably, the interface prototype was applied for the first ever time-resolved on-site analysis of the semivolatile organic fraction of urban air particulate matter (PM2.5).

The biggest limitation to conventional gas chromatography (GC) is limited peak capacity, making the analysis of complex mixtures a difficult or even impossible task. Comprehensive two-dimensional gas chromatography (GC×GC) significantly increases peak capacity and resolution, improves sensitivity and generates structured 3D chromatograms. This is achieved by connecting two columns coated with different stationary phases through a special interface (modulator). The interface samples the first column effluent and periodically injects fractions of this material, as narrow injection pulses, onto the second column for further separation. Commercial instruments achieve this with cryogenic agents. Since this expensive approach permits only in-laboratory analysis, the development of simple, economical and field-capable GC×GC systems is in demand. This report summarizes the fundamentals governing GC×GC separations and a brief history of technological advances in the field. It also documents the construction of a simple interface, devoid of moving parts and cryogenic consumables, and hence highly suitable for field analysis and monitoring applications. Evaluation of the interface suggests on-par performance with more complicated cryogenic modulators. GC×GC separations of technical mixtures of fatty acid methyl esters (FAMEs), common environmental pollutants (EPA 8270), polychlorinated biphenyls (PCBs), pesticides (toxaphene), as well as selected essential oils and major distillation fractions of crude oil indicate very good performance. Most notably, the interface prototype was applied for the first ever time-resolved on-site analysis of the semivolatile organic fraction of urban air particulate matter (PM2.5).

Environmental field analysis provides advantages that allow real-time decisions, interactive sampling and cost effective solutions to the problems faced at the time of investigation. Gas chromatography (GC), a widespread technique for the determination of organic pollutants in the environment, has also shown to be useful in environmental field analysis. Thermal desorption of solid environmental sample provides a technique for liberation of volatile analytes from the samples without the need for solvent extraction. Combining the thermal desorption technique with a field gas chromatograph (GC) thus provides the possibility of on-site determination of organic contaminants in soils. However, to better characterize trace level contaminants in complex sample matrices, laboratory analysis using analytical instrument with great separation and resolution power is required. Comprehensive two-dimensional gas chromatography (GC X GC) is such a powerful analytical tool that provides enhanced separation and resolution capacity for the task. The project presented here involves the development and validation of a field method for the analysis of total polychlorinated biphenyls (PCBs) in soils, and determination of individual PCB congeners in the same samples by further laboratory analysis. The field analytical system developed was a field portable GC interfaced with a thermal desorber. The identification of PCB congeners was realized by a GC X GC system with a time-of-flight mass spectrometer (TOF-MS) as a detector. The field method was developed by optimizing and characterizing the method using PCB standards, followed by the application of the developed method to environmental soil samples. Finally, analyses of PCB congeners in environmental soil samples were performed using the GC X GC system.

Environmental field analysis provides advantages that allow real-time decisions, interactive sampling and cost effective solutions to the problems faced at the time of investigation. Gas chromatography (GC), a widespread technique for the determination of organic pollutants in the environment, has also shown to be useful in environmental field analysis. Thermal desorption of solid environmental sample provides a technique for liberation of volatile analytes from the samples without the need for solvent extraction. Combining the thermal desorption technique with a field gas chromatograph (GC) thus provides the possibility of on-site determination of organic contaminants in soils. However, to better characterize trace level contaminants in complex sample matrices, laboratory analysis using analytical instrument with great separation and resolution power is required. Comprehensive two-dimensional gas chromatography (GC X GC) is such a powerful analytical tool that provides enhanced separation and resolution capacity for the task. The project presented here involves the development and validation of a field method for the analysis of total polychlorinated biphenyls (PCBs) in soils, and determination of individual PCB congeners in the same samples by further laboratory analysis. The field analytical system developed was a field portable GC interfaced with a thermal desorber. The identification of PCB congeners was realized by a GC X GC system with a time-of-flight mass spectrometer (TOF-MS) as a detector. The field method was developed by optimizing and characterizing the method using PCB standards, followed by the application of the developed method to environmental soil samples. Finally, analyses of PCB congeners in environmental soil samples were performed using the GC X GC system.

No description available.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this study, two methods frequently used in the extraction of residues of pesticides in fruits and vegetables, the QuEChERS method and the mini-Luke method, were compared in order to optimize and validate these methods using quantification by GC×GC-μECD. This study was carried out for the pesticides bifenthrin, cyfluthrin, fenpropathrin, fenvalerate, esfenvalerate and permethrin cis and trans in tomato. In the QuEChERS method, 10 mL of acetonitrile containing 1% (v/v) of acetic acid was added to 10 g of sample. In the mini-Luke method, 30 mL of acetone, followed by 60 mL of a 1:1 (v/v) mixture of petroleum ether and dichloromethane were added to 10 g of sample. In the extraction method with acetonitrile, recoveries between 90.2 and 105.5% were obtained with RSD values lower than 8.7%, whereas, using the extraction method with acetone, the recoveries were between 86.2 and 110.8% with RSD values lower than 9.0%. In terms of limit of quantification (LOQ), the QuEChERS method presented values between 0.01 and 0.02 mg kg-1, considered more satisfactory than those obtained using the modified mini-Luke method (LOQ between 0.02 and 0.05 mg kg-1), where the value of LOQ found for cyfluthrin was above of the maximum limit of residues allowed by ANVISA, and therefore unsatisfactory. The r2 values from the analytical curves in the extract of the matrix were equal or higher than 0.9992 and 0.9955 for the modified QuEChERS method and the modified mini-Luke method, respectively, demonstrating that the modified QuEChERS method supplied more appropriate r2 values. Moreover, the QuEChERS method is a simpler procedure as it utilizes manual agitation and can be employed in any laboratory or in the field. Another important advantage of this method is the lower amount of solvent used. This study also showed that the GC×GC-μECD system using a modulator of double compressed air jet reduces costs and can be used in analyses of pyrethroid pesticides in tomato, with satisfactory values of LOD and LOQ, good precision and accuracy. / Nesse estudo comparou-se dois métodos bastante utilizados na extração de resíduos de pesticidas em frutas e vegetais, o método QuEChERS e o método mini-Luke, de modo a otimizar e validar estes métodos utilizando quantificação por GC×GC-μECD. Este estudo foi realizado para os pesticidas bifentrina, ciflutrina, fenpropatrina, fenvalerato, esfenvalerato e permetrina cis e trans em tomate. No método QuEChERS adicionou-se 10 mL de acetonitrila contendo 1% (v/v) de ácido acético em 10 g de amostra. No método mini-Luke adicionou-se 30 mL de acetona, seguidos de 60 mL da mistura 1:1 (v/v) de éter de petróleo e diclorometano em 10 g de amostra. Ao empregar-se o método de extração com acetonitrila obteve-se recuperações entre 90,2 e 105,5% com RSD menor que 8,7%, enquanto que, utilizando o método de extração com acetona, as recuperações ficaram entre 86,2 e 110,8% com RSD menor que 9,0%. Em termos de limite de quantificação (LOQ) o método QuEChERS modificado apresentou valores entre 0,01 e 0,02 mg kg-1, considerados mais satisfatórios que os obtidos pelo método mini-Luke modificado (LOQ entre 0,02 e 0,05 mg kg-1), sendo que, neste caso, o valor de LOQ encontrado para ciflutrina não foi satisfatório, pois está acima do limite máximo de resíduos permitido pela ANVISA. Com relação aos valores de r2 das curvas analíticas, percebeu-se que, utilizando o método QuEChERS modificado estes valores foram maiores ou iguais a 0,9992 e para o método mini-Luke modificado foram maiores ou iguais a 0,9955, ambos para as curvas no extrato da matriz, demonstrando, portanto, que o método QuEChERS modificado forneceu valores de r2 mais apropriados. Além disso, o método QuEChERS mostrou ser um procedimento mais simples por utilizar agitação manual, podendo ser aplicado em qualquer laboratório ou a campo. Outra vantagem importante deste método é a menor quantidade de solvente utilizado. Este estudo mostrou também que o sistema GC×GC-μECD com modulador de duplo jato de ar comprimido possibilita a redução dos custos da análise e que esta combinação pode ser utilizada em análises de pesticidas piretróides em tomate, pois obteve-se valores satisfatórios de LOD e LOQ, com boa precisão e exatidão.

Depuis plusieurs siècles les racines de vétiver sont utilisées en Inde du sud afin de prévenir l'érosion du sol. Par la suite, la production de l’huile essentielle des racines de vétiver a permis d’alimenter l’industrie de la parfumerie. De nos jours, cette matière première sert principalement à la confection de parfums masculins, où elle apporte des notes boisées, terreuses, de pamplemousse et de rose. En dépit de son utilisation abondante, la nature des molécules responsables de son odeur est encore un sujet de controverses. Dans un premier temps, l’étude des constituants volatils a été entreprise, et certaines incohérences de la littérature ont été mises en évidence. Par la suite, l'analyse par GC × GC d'huiles de vétiver d'origines différentes a permis de mieux comprendre la variabilité de cette matière première. Elle a également facilité l’identification de substances odorantes d'impact, réalisée par GC-O sur l’huile essentielle et l’acétate de vétiveryle. La synthèse de plusieurs dérivés zizaane a également été développée pour confirmer certains des résultats de la caractérisation des odorants. Nous avons également développé une nouvelle procédure pour la synthèse à grande échelle de dérivés nor-zizaane à puissante odeur de vétiver. Lors de cette étude, nous avons développé une nouvelle réaction de décarbonylation utilisant le peroxyde d'hydrogène en milieu alcalin. Cette réaction a pu être appliquée sur différents aldéhydes aliphatiques, les meilleurs résultats étant obtenus avec des substrats α-disubstitués. Une bonne sélectivité a également pu être observée sur les aldehydes linéaires, qui conduisent généralement à l’acide dans de telles conditions. / Vetiver have been used from centuries in South India to prevent soil erosion and later on, the essential oil produced by distillation of this raw material has begun to been largely employed in perfume composition. This essential oil is now abundantly used in the confection of men perfumes for its pleasant fragrance of wood, earth, grapefruit and rose. However, paradoxically, the nature of its impact odorants still remains controversial. At first, we have realized the review of the volatile constituents identified in this material, and some discrepancies of the literature have been highlighted. Then, the analysis by GC × GC of vetiver oils from different origins has permitted to better understand the composition of these materials. Subsequently, the characterization of the impact odorants of Haitian vetiver essential oil and vetiveryl acetate has been performed by GC-O. To confirm some of the results of this investigation, several zizaane derivatives have been synthesized, and in the course of this study, we developed a new reaction of decarbonylation of aliphatic aldehydes using alkaline hydrogen peroxide. A new procedure for the large scale preparation of highly potent nor-zizaane odorants could then be developed. Moreover, when exploring the scope and limitations of this reaction, it appeared to be applicable on various aliphatic aldehydes. The best results were obtained with α-disubstituted substrates, and a surprisingly good selectivity of this reaction was noticed on linear aldehydes.

The grape is one of the oldest cultivated plants. It can be consumed as a fruit or it can be used as a raw material for making stews, juices or the cultivated drink – wine. Generations of wine-makers have been striving to improve both the cultivating conditions of vineyards and the quality of wine. Many harmful elements, such as herbivorous pests, diseases and storms are important factors that can have a negative impact on crop quality. To regulate the effects of these factors, an integrated protection system is used, incorporating agronomical measures, resistant varieties and a wide spectrum of pesticides. However, increasing the usage of pesticides brings certain dangers to both the production quality and the environment. This necessitates the monitoring of the negative effects, including the content of pesticide residues in the grapes. My thesis studies and experimentally assesses selected pesticide residues in certain wine samples.

Isoprenoids are important components of conifer resin and represent an important part of constituted defence system against herbivores and pathogens. Drought is one of the most important factors that influences the tree physiology and resitance. Due to decreased turgor of resin canal cells, the water insufficiency affects the pressure of the resin and thereby the ability of trees to physically prevent pathogen or herbivore invasion by effective outpouring of the resin. In addition, drought can also change the resin composition and thus can influence the quality of volatiles emitted by the tree. The Norway spruce, Picea abies, is the predominant species of production forests in moderate climate zone. Bark beetles, Ips typographus, represent the most important pest species of spruce. In general, pioneer bark beetles use host volatiles to orient themselves toward the tree suitable for colonization and in many species host volatiles synergize bark beetle aggregation pheromones. Thus the host volatile composition could affect significantly host colonization. This diploma thesis studied the influence of drought on the production and composition of isoprenoid volatile organic compounds in 80 - 100 years old spruce trees. Using I. typographus antennae as biological detectors, we also studied which resin...