Several methods have been used for the characterisation of minerals in powders and in rocks. Particular emphasis has been directed towards the use of chemical probes to elucidate the surface mineralogy in order to provide detection profiles suitable for both qualitative and quantitative chemometric analysis. The first probe evaluated was cyclohexylamine (CHA). Ni[2+]- and Al[2+]-exchanged montmorillonite (SWy-2 -Wyoming, USA), were exposed to cyclohexylamine vapour (CHA). The samples were characterised by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and evolved gas analysis (EGA), which included TGA, real time gas phase FTIR (RT-GP-FTIR), real time mass spectrometry (RT-MS) and organic trap module-gas chromatography-mass spectrometry (OTM-GC-MS). CHA decomposed along different routes via interrelated mechanisms that were cation dependent. Over Al[3+]-SWy-2 hydrodenitrogenation via the Hofmann degradation was the predominant route whereas ring dehydrogenation to aniline either directly from CHA or possibly via cyclohexylimine was significant over Ni[2+]-SWy-2. Very little unmodified cyclohexylamine was detected in the evolved gases which means that the desorption of CHA cannot be used as a quantitative measure of the acidity of cation-exchanged clays. Nonetheless, as a qualitative probe, CHA has the potential to distinguish the difference between Ni[2+] and Al[3+]-SWy-2.The second probe evaluated was 3-cyanopyridine (3CYP). TGA has shown that temperature programmed desorption (TPD) of 3CYP is capable of distinguishing between the Ni[2+]- and Al[3+] exchanged forms of SWy-2. 3CYP was found to be unsuitable for a variety of reasons highlighted by its ability to condense within the EGA system and the long incubation times necessary to produce detectable thermal events. The most suitable probe used so far is Dimethylformamide (DMF), being able to intercalate quickly and showing no evidence of modification. Principal component analysis (PCA) and partial least squares (PLS) modelling techniques were applied to the EGA DMF detection profiles of four clay mineral groups. Each group was successfully characterised and provided valuable information about intra and inter group relationships. The use of RT-MS detection profiles for ions m/z =18 and 73 (DMF parent ion) were shown to have the most potential for more sensitive quantitative applications. Application of quantitative PLS modelling to mixed mineral standards has shown that it is possible to estimate the clay mineral constituents in both powders and rocks. The use of the ion m/z = 73 provided an R[2] value of 0.98. Use of ion m/z =18 (H[2]O) has perhaps shown most potential, due to its ability to produce training sets with excellent correlation coefficients of 0.95 for SWy-2, 0.97 for KGa-2 and 0.95 for CCa-1. However, because SWy-2 and 1-Mt (illite) demonstrate overlapping detection of DMF (where uptake of DMF by 1-Mt is comparatively small), it is impossible to directly separate their relative contributions at the concentration levels under study. The use of mass spectrometry has shown that it is possible to detect to levels of 1% with considerable scope for detecting smaller levels. Environmental scanning electron microscope (ESEM) and energy dispersive X-ray analysis (EDX) of cation exchanged SWy-2 and a sandstone rock exposed to 2-bromopyridine (2BPY) have shown the potential of using the bromine functional group as a tag to locate the presence of swelling minerals in rocks by EDX.

No description available.

Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2016-08-29T13:03:19Z No. of bitstreams: 1 PDF - José Celson Braga Fernandes.pdf: 4224214 bytes, checksum: c224aab992d418111936ca2d4f0143ed (MD5) / Approved for entry into archive by Secta BC (secta.csu.bc@uepb.edu.br) on 2016-08-29T17:03:12Z (GMT) No. of bitstreams: 1 PDF - José Celson Braga Fernandes.pdf: 4224214 bytes, checksum: c224aab992d418111936ca2d4f0143ed (MD5) / Made available in DSpace on 2016-08-29T17:03:12Z (GMT). No. of bitstreams: 1 PDF - José Celson Braga Fernandes.pdf: 4224214 bytes, checksum: c224aab992d418111936ca2d4f0143ed (MD5) Previous issue date: 2016-04-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / With the great demand for renewable energy sources, biodiesel stands out as promising in this business presenting character of sustainability, it is promising in this area and it is recommended by public policies its use with diesel, but its quality is of utmost importance since, with tamper product quality result in serious damage to the end consumer, damage to equipment as well as contributing to pollution. Therefore, this study aimed to use tools that help and contribute in determining the physical-chemical parameters of blends of biodiesels castor and peanut, facilitating adoption of techniques to better performance of its implementation in the laboratory activities and adoption of non-destructive techniques , it was soon made conventional chemical physical readings and applied to these one desirability function and chemometric techniques with readings in the NIR and later applied the Ispa-PLS algorithm to determine the best conditions of mixtures of biodiesels. According to the techniques used, it can be determined that the best conditions for biodiesel blends, castor peanuts were to mix consisting of 25% castor oil 75% peanut, with a = 0.67 and D according to the algorithm iSPA- PLS were the best conditions (MSC) global PLS, with a RMSECV 0.16 and 0.88 R2 for predicting with 9 latent variables. Thus, it can be concluded that the proposed methodologies are promising analytical tools for monitoring biodiesel quality in terms of their physical and chemical parameters. / Com as grandes demandas por fontes de energias renováveis, o biodiesel destaca-se como promissor nesse ramo, apresentando caráter de sustentabilidade. Através de políticas públicas é recomendado a sua inserção junto ao diesel, porém a sua qualidade é de extrema importância, uma vez que, havendo adulteração na qualidade do produto resultará em sérios danos ao consumidor final, com a danificação de equipamentos, bem como, contribuindo para a poluição. Portanto, este trabalho objetivou usar ferramentas que auxiliem e que contribuam na determinação dos parâmetros físico-químicos e relação à preservação das amostras e tempo gasto de misturas de biodieseis de mamona e amendoim, facilitando adoção de técnicas, que visam um melhor desempenho de sua execução nas atividades laboratoriais, bem como adoção de técnicas não destrutivas. Logo, foram realizadas, leituras físico-químicas convencionais e aplicado a estas, uma função de desejabilidade e técnicas quimiométricas com leituras no NIR e posteriormente aplicado o algoritmo iSPA-PLS, para determinação de melhores condições das misturas de biodieseis. De acordo com as técnicas empregadas, pode-se determinar as melhores misturas de biodieseis, mamona amendoim onde resultou na mistura composta por 25% de mamona 75% amendoim, apresentando uma D=0,67 e de acordo com o algoritmo iSPA-PLS a 2 melhor modelo foi o (MSC) PLS global, apresentando um RMSECV 0,16 e um R 0,88 para predição com 9 variáveis latentes. Assim, pode-se concluir que as metodologias propostas são ferramentas analíticas promissoras, para a monitorização da qualidade do biodiesel, em termos de seus parâmetros físico-químicos.

The ultimate goal of this research is to provide a low cost, efficient, reproducible, quantitative, non-invasive screening method to diagnose diseases at an early stage through identification of volatile biomarkers of disease. Progress has been made in the areas towards development of an analytical system that can provide a rapid and specific assay for above mentioned Volatile Organic Compounds (VOCs). (i) Methods have been designed for the collection, concentration, identification and quantification of volatile biomarkers. (ii) Advanced signal processing evaluation of data has tentatively identified key VOCs patterns with breath and body odor. (iii) Novel absorbent coatings have been studied for use with miniature chemical sensors that one day may be part of a portable analytical system. Both breath and body odor contain a complex mixture of chemicals, which are influenced by many internal and external factors. Breath and skin odor samples were collected with minimum external contaminations using traditional SPME and active SPME GCMS techniques. Body odor from 65 human subjects was tested with and without selected scent removal products. Breath samples were collected from 21 canine subjects. The VOCs profiles of these samples were determined and then statistically treated with principal component analysis, discriminant analysis, and tree regression techniques to simplify and interpret the complex mixtures. While much of our work has utilized large bench-top equipment, our over-arching goal is to provide a portable device that can diagnose diseases at an early stage. Concurrent work was done to enhance the performance of a miniaturized detector for the detection of potential biomarkers. Two organic polymers mixed with conductive carbon nanoparticles were deposited between the microcapacitor plates of microsensors using ink-jet technology. Microsensors were also fabricated using conducting ionic liquids. The performances of the individual chemicapacitive sensors were characterized through exposure to different concentrations of varied volatile organic compounds with different functional groups in a climate-controlled vapor delivery system.

Orientador: Ronei Jesus Poppi / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-22T20:20:45Z (GMT). No. of bitstreams: 1 Terra_LucianaAssis_M.pdf: 5662002 bytes, checksum: 969f678029bf9ac1f5d8f5fadf9727f9 (MD5) Previous issue date: 2013 / Resumo: A Espectroscopia de Imagem na região do Infravermelho Próximo juntamente com ferramentas quimiométricas foi utilizada para estudar a transformação polimórfica do fármaco carbamazepina (forma III para forma I) em formulações farmacêuticas do comprimido, geradas por aquecimento. Os mapas de distribuição de concentração das formas polimórficas I e III da carbamazepina no comprimido foram estimados por Mínimos Quadrados Parciais (PLS), Resolução Multivariada de Curvas (MCR) e Análise de Fatores Paralelos (PARAFAC), assim como o perfil de concentração em função do tempo durante o aquecimento, comparando os resultados obtidos quanto à eficácia na quantificação das formas polimórficas. Para o estudo da homogeneidade da distribuição do fármaco ao longo do comprimido, foram construídos histogramas. O trabalho está dividido em duas partes: na primeira parte foi realizado o mapeamento completo de um comprimido antes e após o aquecimento a 160 ºC, por 3 horas e os dados foram analisados por MCR. Na segunda parte do trabalho estudou-se a transformação polimórfica com o tempo a 140 ºC, em que foi realizado o mapeamento da parte central do comprimido, sendo nesse caso obtidas imagens a cada hora, com tempo total de 7 horas. Os resultados mostraram que os métodos PLS, MCR e PARAFAC foram capazes de obter informações sobre a transformação polimórfica, sendo MCR e PARAFAC capazes de estudar o processo dinâmico envolvido. Além disso, o MCR também foi capaz de fornecer os mapas de distribuição de concentrações em cada tempo de aquisição de dados, acompanhando a transformação polimórfica na superfície do comprimido / Abstract: The Near Infrared Chemical Imaging in conjunction with chemometric tools was used to study the polymorphic transformation of the drug carbamazepine (form III to form I) in pharmaceutical formulations tablets, generated by heating. The concentration distribution maps of the polymorphic forms I and III of carbamazepine in the tablet were estimated by Partial Least Squares (PLS), Multivariate Curve Resolution (MCR) and Parallel Factor Analysis (PARAFAC), as well as the concentration profile as a function of the heating time and the results were compared regarding the efficacy in quantification of the polymorphic forms. For the study of the homogeneity of distribution of the drug in the tablet, histograms were built. The work was divided into two parts: in the first part, it was conducted the mapping of the whole tablet before and after heating at 160 ºC for 3 hours and the data were analysed by MCR. In the second part, it was studied the polymorphic transformation over the time at 140 °C. Images of the central part of the tablet were obtained every hour during 7 hours. The results showed that the PLS, MCR and PARAFAC were able to obtain information about the polymorphic transformation and the MCR and PARAFAC were able to study the dynamic process involved as well. Furthermore, the MCR provided the concentration distribution map at each time of data acquisition, providing the polymorphic transformation on the tablet surface / Mestrado / Quimica Analitica / Mestra em Química

De nombreux systèmes biologiques sont intrinsèquement polydispersés, présentant de multiples espèces coexistantes, de taille, de forme ou de conformation différentes (c'est-à-dire, mélanges oligomèriques, des complexes faiblement liés se dissociant en composantes individuelles ou des espèces apparaissant lors de processus amyloïdogéniques). L'étude de tels systèmes complexes est une tâche difficile en raison de l'instabilité des espèces concernées, de leurs concentrations relatives faibles et interdépendantes et des difficultés rencontrées pour l'isolation des composantes pures. Dans cette thèse, j'ai développé des approches méthodologiques pour appliquer la diffusion des rayons X aux petits angles (SAXS), une technique de biologie structurale, à l'étude de systèmes polydispersés. SAXS est une technique additive et par conséquent, le diagramme de diffusion mesuré pour un échantillon polydispersé correspond à la somme pondérée en concentration des contributions de chacune des composantes individuelles du mélange. Cependant, la décomposition des données de SAXS en des spectres spécifiques des espèces et de leurs concentrations relatives est extrêmement laborieuse et ambigue. Dans cette thèse, je présente d'abord une approche objective pour solidement décomposer les jeux de données de SAXS en composantes individuelles. Cette approche adapte la méthode chimiométrique « Multivariable Curve Resolution Alternate Least Squares » (MCR-ALS) aux spécificités des données de SAXS. Notre méthode permet une décomposition rigoureuse et robuste des données de SAXS en introduisant simultanément différentes représentations de ces données et par conséquent, en mettant l'accent sur des changements moléculaires à différentes plages de temps et de résolution structurale. Nous avons appliqué cette approche, que nous appelons COSMiCS (Analyse structurelle objective complexe des systèmes multi-composants) pour étudier deux systèmes polydispersés: la fibrillation des protéines, et les fluctuations conformationnelles de protéines grâce à l'analyse de données obtenues à l'aide d’une technique de couplage de chromatographie d'exclusion de taille (SEC) avec le ligne de SAXS (SEC-SAXS). L'importance d'étudier les processus de fibrillation réside dans leur implication dans des pathologies amyloïdogéniques telles que les maladies de Parkinson ou d'Alzheimer. Il existe de fortes indications que les espèces oligomériques solubles, et non les fibrilles matures, sont la cause principale de la cytotoxicité et des dommages neuronaux. Cette observation souligne l'importance de caractériser les premiers stades des processus de fibrillation. Notre approche COSMiCS a permis d'étudier les processus amyloïdogéniques de l'insuline et du mutant familial E46K de l'α-synucléine, une protéine associée à la maladie de Parkinson. Cette analyse permet la caractérisation structurale des espèces présentes (y compris les espèces oligomériques) et la caractérisation cinétique de leurs transformations.La deuxième partie de la thèse est consacrée à l'utilisation de COSMiCS pour analyser des données de SEC-SAXS. Le SEC-SAXS est extrêmement populaire et a été implémenté sur plusieurs lignes de SAXS à travers le monde. En utilisant des données synthétiques, je démontre la capacité des approches chimiométriques à décomposer des profils chromatographiques complexes. À l'aide de cette approche, j'ai décomposé l’ensemble des données SEC-SAXS mesurés pour la Prolyl OligoPeptidase (POP).En résumé, cette thèse présente une nouvelle approche chimiométrique qui peut être généralement appliquée à tout mélange macromoléculaire pouvant subir une modifacation de son équilibre et pouvant être abordé par SAXS. Les complexes biomoleculaires transitoires, les processus de repliement, les réarrangements structuraux dépendants d’un ligand ou la formation de grands ensembles supramoleculaires peuvent être sondés de façon structurale en utilisant l'approche COSMiCS. / Many biological systems are inherently polydisperse, presenting multiple coexisting species differing in size, shape or conformation (i.e. oligomeric mixtures, weakly bound complexes, and species appearing along amyloidogenic processes). The study of such complex systems is challenging due to the instability of the species involved, their low and interdependent relative concentrations, and the difficulties to isolate the pure components. In this thesis, I have developed methodological approaches to apply Small-Angle X-ray Scattering (SAXS), a low-resolution structural biology technique, to the study of polydisperse systems. As an additive technique, the SAXS pattern measured for a polydisperse sample corresponds to the concentration-weighted sum of the contributions from each of the individual components. However, decomposition of SAXS data into species-specific spectra and relative concentrations is laborious and burdened by ambiguity. In this thesis, I present an approach to decompose SAXS datasets into the individual components. This approach adapts the chemometrics Multivariate Curve Resolution Alternating Least Squares (MCR-ALS) method to the specificities of SAXS data. Our method enables the rigorous and robust decomposition of SAXS data by simultaneously introducing different representations of these data and, consequently, emphasizing molecular changes at different time and structural resolution ranges. We have applied this approach, which we name COSMiCS (Complex Objective Structural analysis of Multi-Component Systems), to study two polydisperse systems: amyloid fibrillation by analysing time-dependent SAXSdata, and conformational fluctuations through the analysis of data obtained using on-line size-exclusion chromatography coupled to SAXS (SEC-SAXS). The importance of studying fibrillation processes lies in their implication in amyloidogenic pathologies such as Parkinson’s or Alzheimer’s diseases. There exist strong indications that soluble oligomeric species, and not mature fibrils, are the main cause of cytotoxicity and neuronal damage emphasizing the importance of characterizing early stages of fibrillation. The first application of our COSMiCS approach has allowed the study of the amyloidogenic mechanisms of insulin and the familial mutant E46K of ↵-synuclein, a Parkinson’s disease related protein. The analysis enables the structural characterization of all the species present as well as their kinetic transformations. The second part of the thesis is dedicated to the use of COSMiCS to analyze on-line SEC-SAXS experiments. Using synthetic data, I demonstrate the capacity of chemometric approaches to decompose complex chromatographic profiles. Using this approach, I have studied the conformational fluctuations in prolyl oligopeptidase (POP), a protein related to synaptic functions and neuronal development. In summary, this thesis presents a novel chemometrics approach that can be generally applied to any macromolecular mixture with a tuneable equilibrium that is amenableto SAXS. Transient biomolecular complexes, folding processes, or ligand-dependent structural rearrangements can be probed structurally using COSMiCS.

Soil contamination from petroleum spills is a frequent environmental problem in the world. It is obvious that petroleum exploration has contributed immensely to the economic growth of Nigeria, but over the last few decades, the Niger Delta of Nigeria has suffered grave human health risk and ecosystem degradation resulting from oil spillages, petroleum products leakages and other involuntary effluent discharges from oil exploration activities. This research seeks to develop and optimize GC-FID methods for the analysis of Petroleum hydrocarbons. Crude oil spillage contamination of soil from the Niger Delta was investigated 3 months after a crude oil-pipeline spillage. 47 Soil samples (300-500g) were collected at several points in the South-South Niger Delta. Control samples were taken from four unaffected sites within the vicinity of spillage with similar soil characteristics. Samples were collected at depths of 0-15 cm, 15-30 cm and 30-60 cm. The soil samples were prepared for analysis using solvent extraction methods, passed through column of sodium sulphate and Florisil® to aid in column performance, remove moisture and gross impurities. Samples were analysed using gas chromatography with a flame ionisation detector. Penetration and migration of C10-C26 and C26-C34 hydrocarbons through the soil layers were assessed by cluster analysis to determine the spatial distribution, penetration and chemical similarity of these compounds over the contaminated area. This information is a useful guide for bioremediation purpose. It was found that total petroleum hydrocarbon concentrations varied from 9-289 mgkg-1 topsoil, 8-318 mgkg-1 subsoil and 7-163 mgkg-1 at the greatest depth measured.The results show elevated levels of total hydrocarbon contents when compared with the reference sites. Drastic steps should be taken to carefully monitor and remediate the environment. Bioremediation with plants and micro-organisms is endorsed.

In the first part of this work, LC-MS data were used to calculate the in-vitro intrinsic clearances (CLint) for the metabolism of p-methoxyrnethamphetamine (PMMA) and fluoxetine by the CYP2D6 enzyme using a steady-state (SS) approach and a new general enzyme (GE) screening method. For PMMA, the SS experiment resulted in a CLint of 2.7 ± 0.2 µL pmol 2D6-1min-1 and the GE experiment resulted in a CLint of 3.0 ± 0.6 µL pmol 2D6-1min-1. For fluoxetine, the SS experiment resulted in a CLint of 0.33 ± 0.17 µL pmol 2D6-1min-1 and the GE experiment resulted in a CLint of 0.188 ± 0.013 µL pmol 2D6-1min-1. The inhibition of PMMA metabolism by fluoxetine was also demonstrated.In the second part of the work, target factor analysis was used as part of a library search algorithm for the identification of drugs in LC-DAD chromatograms. The ability to resolve highly overlapped peaks using the spectral data afforded by the DAD is what distinguished this method from conventional library searching methods. A validation data set of 70 chromatograms was used to calculate the sensitivity (correct identification of positives) and specificity (correct identification of negatives) of the method, which were 92% and 94% respectively.Finally, the last part of the work shows the development of data analysis methods for four-way data generated by two-dimensional liquid chromatography separations with DAD. Maize seedlings were analyzed, specifically focusing on indole-3-acetic acid (IAA) and related compounds. Window target testing factor analysis was used to identify the spectral groups represented by the standards in the mutant and wild-type chromatograms. Two curve resolution algorithms were applied to resolve overlapped components in the data and to demonstrate the quantitative potential of these methods. A total of 95 peaks were resolved. Of those peaks, 45 were found in both the mutant and wild-type maize, 16 peaks were unique to the mutants, 13 peaks were unique to the wild-types, and the remaining peaks were standards. Several IAA conjugates were quantified in the maize samples at levels of 0.3 - 2 µg/g plant material.

Métodos analíticos empregando técnicas eletroquímicas foram desenvolvidos para o monitoramento qualitativo e quantitativo de pesticidas carbamatos. O sensor utilizado no desenvolvimento dos métodos foi o eletrodo de diamante dopado com boro pré-tratado catodicamente. No desenvolvimento do método qualitativo, foi possível discriminar e classificar cinco pesticidas carbamatos (aldicarb, carbaril, carbofurano, metomil e propoxur) com a ajuda de ferramentas quimiométricas, tais como análise de componentes principais e do algoritmo dos k-vizinhos mais próximos. Nesse método, os valores de corrente, obtidos por voltametria de onda quadrada, para os pesticidas foram utilizados como dados de entrada nas ferramentas quimiométricas. Um método eletroquímico, utilizando voltametria de pulso diferencial, para a quantificação do pesticida propoxur foi desenvolvido. Após a otimização dos parâmetros da técnica e das condições experimentais, construiu-se uma curva analítica de 1,66 a 155 µmol L-1 (R2 = 0,9935) e limite de detecção estimado de 0,50 µmol L-1. A exatidão do método foi avaliada por adição e recuperação em amostras de águas naturais, onde se alcançou níveis de recuperação na faixa de 86,7 a 103%. Para o pesticida pirimicarbe, foi realizado um amplo estudo visando elucidar o comportamento eletroquímico de oxidação desse composto, o qual foi suportado por dados de espectrometria de massas. Na faixa de pH estudada (2 a 8), o pirimicarbe apresentou três sinais de oxidação irreversíveis, sendo os dois primeiros dependentes do pH. Por outro lado, em experimento realizado em meio orgânico, evidenciou a presença de apenas um sinal de oxidação para o pesticida. Também foi desenvolvido um método eletroquímico por voltametria de pulso diferencial para a quantificação do pirimicarbe. Os parâmetros da técnica de voltametria de pulso diferencial foram otimizados utilizando planejamento experimental. A curva analítica apresentou faixa de trabalho de 2,00 a 219 µmol L1-1 (R2 = 0,9982) e limite de detecção estimado de 1,24 µmol L-1. O método de adição e recuperação juntamente com calibração externa foram utilizados para avaliação da exatidão do método em amostras de águas naturais, obtendo-se recuperações entre 88,6 e 96,3%. Adicionalmente, um método para a quantificação do pesticida paraquate foi desenvolvida utilizando a técnica de voltametria de onda quadrada. O pesticida apresentou dois sinais de redução reversíveis e com magnitude de corrente semelhantes, portanto, sendo possível utilizar qualquer um dos dois sinais para sua quantificação. Com a otimização dos parâmetros da técnica e das condições experimentais, foi possível obter uma curva analítica na faixa de 0,800 a 167 µmol L-1 (R2 = 0,9990) e limite de detecção estimado em 70 nmol L1-1. O método foi aplicado em amostras de saliva humana e águas naturais e níveis de recuperação na faixa de 83,0 a 105% foram alcançados. Vale ressaltar que todos os métodos analíticos aqui propostos apresentaram simplicidade, confiança e podem ser considerados adequados tanto para análises de rotina quanto para aplicações em campo, devido à portabilidade apresentada pelos métodos eletroquímicos. / Electroanalytical methods were developed for the qualitative and quantitative monitoring of carbamate pesticides. The sensor used for the development of the proposed methods was the boron-doped diamond electrode cathodically pre-treated. In the development of the qualitative method, it was possible to discriminate and classify five carbamate pesticides (aldicarb, carbaryl, carbofuran, methomyl and propoxur) using chemometric tools such as principal component analysis and the k-nearest neighbors algorithm. In qualitative approach, current values obtained by square-wave voltammetry for pesticides were used as input data of the chemometric tools. An electrochemical method, using differential pulse voltammetry, for the quantification of pesticide propoxur was also developed. At the best conditions (parameters of the technique and the experimental conditions), an analytical curve from 1.66 to 155 µmol L-1 (R2 = 0.9935) and an estimated detection limit of 0.50 µmol L-1 were obtained. The accuracy of the method was evaluated by addition and recovery approach in natural waters samples and recovery levels ranging from 86.7 to 103% were reached. For the pesticide pirimicarb, a study was carried out to elucidate the electrochemical oxidation behavior of this compound, which was supported by mass spectrometry data. In the pH range (2 to 8) studied, the pirimicarb shown three irreversible oxidation signals, the first two were pH-dependent. On the other hand, in an experiment carried out in organic medium, it exhibited the presence of only one oxidation signal for the pesticide. An electrochemical method was also developed by differential pulse voltammetry for the quantification of pirimicarb. The parameters of the differential pulse voltammetry technique were optimized using experimental design. The analytical curve showed a working range from 2.00 to 219 µmol L-1 (R2 = 0.9982) and an estimated detection limit of 1.24 µmol L-1. The addition and recovery approach with external calibration were used to evaluate the accuracy of the method in natural water samples, obtaining recoveries values between 88.6 and 96.3%. In addition, a method for the quantification of the paraquat pesticide was developed using the square-wave voltammetry technique. The pesticide presented two reversible reduction signals with similar current magnitude, therefore, it is possible to use either of the two signals for its quantification. Under optimized parameters of the technique and the experimental conditions, it was possible to obtain an analytical curve in the range from 0.800 to 167 µmol L-1 (R2 = 0.9999) and detection limit estimated of 70 nmol L-1. This method was applied for human saliva and natural water samples and recovery levels ranging from 83.0 to 105% were achieved. It should be noted that all the analytical methods proposed here exhibited simplicity, reliability and can be considered adequate for routine analysis and in-field applications due to the portability characteristics of the electrochemical methods.

Métodos analíticos empregando técnicas eletroquímicas foram desenvolvidos para o monitoramento qualitativo e quantitativo de pesticidas carbamatos. O sensor utilizado no desenvolvimento dos métodos foi o eletrodo de diamante dopado com boro pré-tratado catodicamente. No desenvolvimento do método qualitativo, foi possível discriminar e classificar cinco pesticidas carbamatos (aldicarb, carbaril, carbofurano, metomil e propoxur) com a ajuda de ferramentas quimiométricas, tais como análise de componentes principais e do algoritmo dos k-vizinhos mais próximos. Nesse método, os valores de corrente, obtidos por voltametria de onda quadrada, para os pesticidas foram utilizados como dados de entrada nas ferramentas quimiométricas. Um método eletroquímico, utilizando voltametria de pulso diferencial, para a quantificação do pesticida propoxur foi desenvolvido. Após a otimização dos parâmetros da técnica e das condições experimentais, construiu-se uma curva analítica de 1,66 a 155 µmol L-1 (R2 = 0,9935) e limite de detecção estimado de 0,50 µmol L-1. A exatidão do método foi avaliada por adição e recuperação em amostras de águas naturais, onde se alcançou níveis de recuperação na faixa de 86,7 a 103%. Para o pesticida pirimicarbe, foi realizado um amplo estudo visando elucidar o comportamento eletroquímico de oxidação desse composto, o qual foi suportado por dados de espectrometria de massas. Na faixa de pH estudada (2 a 8), o pirimicarbe apresentou três sinais de oxidação irreversíveis, sendo os dois primeiros dependentes do pH. Por outro lado, em experimento realizado em meio orgânico, evidenciou a presença de apenas um sinal de oxidação para o pesticida. Também foi desenvolvido um método eletroquímico por voltametria de pulso diferencial para a quantificação do pirimicarbe. Os parâmetros da técnica de voltametria de pulso diferencial foram otimizados utilizando planejamento experimental. A curva analítica apresentou faixa de trabalho de 2,00 a 219 µmol L1-1 (R2 = 0,9982) e limite de detecção estimado de 1,24 µmol L-1. O método de adição e recuperação juntamente com calibração externa foram utilizados para avaliação da exatidão do método em amostras de águas naturais, obtendo-se recuperações entre 88,6 e 96,3%. Adicionalmente, um método para a quantificação do pesticida paraquate foi desenvolvida utilizando a técnica de voltametria de onda quadrada. O pesticida apresentou dois sinais de redução reversíveis e com magnitude de corrente semelhantes, portanto, sendo possível utilizar qualquer um dos dois sinais para sua quantificação. Com a otimização dos parâmetros da técnica e das condições experimentais, foi possível obter uma curva analítica na faixa de 0,800 a 167 µmol L-1 (R2 = 0,9990) e limite de detecção estimado em 70 nmol L1-1. O método foi aplicado em amostras de saliva humana e águas naturais e níveis de recuperação na faixa de 83,0 a 105% foram alcançados. Vale ressaltar que todos os métodos analíticos aqui propostos apresentaram simplicidade, confiança e podem ser considerados adequados tanto para análises de rotina quanto para aplicações em campo, devido à portabilidade apresentada pelos métodos eletroquímicos. / Electroanalytical methods were developed for the qualitative and quantitative monitoring of carbamate pesticides. The sensor used for the development of the proposed methods was the boron-doped diamond electrode cathodically pre-treated. In the development of the qualitative method, it was possible to discriminate and classify five carbamate pesticides (aldicarb, carbaryl, carbofuran, methomyl and propoxur) using chemometric tools such as principal component analysis and the k-nearest neighbors algorithm. In qualitative approach, current values obtained by square-wave voltammetry for pesticides were used as input data of the chemometric tools. An electrochemical method, using differential pulse voltammetry, for the quantification of pesticide propoxur was also developed. At the best conditions (parameters of the technique and the experimental conditions), an analytical curve from 1.66 to 155 µmol L-1 (R2 = 0.9935) and an estimated detection limit of 0.50 µmol L-1 were obtained. The accuracy of the method was evaluated by addition and recovery approach in natural waters samples and recovery levels ranging from 86.7 to 103% were reached. For the pesticide pirimicarb, a study was carried out to elucidate the electrochemical oxidation behavior of this compound, which was supported by mass spectrometry data. In the pH range (2 to 8) studied, the pirimicarb shown three irreversible oxidation signals, the first two were pH-dependent. On the other hand, in an experiment carried out in organic medium, it exhibited the presence of only one oxidation signal for the pesticide. An electrochemical method was also developed by differential pulse voltammetry for the quantification of pirimicarb. The parameters of the differential pulse voltammetry technique were optimized using experimental design. The analytical curve showed a working range from 2.00 to 219 µmol L-1 (R2 = 0.9982) and an estimated detection limit of 1.24 µmol L-1. The addition and recovery approach with external calibration were used to evaluate the accuracy of the method in natural water samples, obtaining recoveries values between 88.6 and 96.3%. In addition, a method for the quantification of the paraquat pesticide was developed using the square-wave voltammetry technique. The pesticide presented two reversible reduction signals with similar current magnitude, therefore, it is possible to use either of the two signals for its quantification. Under optimized parameters of the technique and the experimental conditions, it was possible to obtain an analytical curve in the range from 0.800 to 167 µmol L-1 (R2 = 0.9999) and detection limit estimated of 70 nmol L-1. This method was applied for human saliva and natural water samples and recovery levels ranging from 83.0 to 105% were achieved. It should be noted that all the analytical methods proposed here exhibited simplicity, reliability and can be considered adequate for routine analysis and in-field applications due to the portability characteristics of the electrochemical methods.