L'objectif du travail de recherche mené concerne l'élaboration des nouveaux matériaux d'électrodes modifiés pour des applications dans le domaine des biocapteurs. Le travail a été subdivisé en trois parties portant sur le greffage du sel de diazonium pour application immunocapteur, l'électroadressage des d'anticorps et l'électrodépôt d'un espaceur pour application aptacapteur. Dans la première partie de ce travail, nous nous sommes consacrés d'abord à l'électrogreffage du nitrobenzène diazonium sur la surface d'or pour le développement de capteurs immunologiques destinés à la détection de la bactérie Staphylococcus aureus. Une limite de détection de 10 UFC/mL a été atteinte. Dans la deuxième partie, la détection de l'ochratoxine A est présentée, basée sur l'électroadressage covalent de l'anticorps modifié par la fonction diazonium sur des électrodes de Diamant Dopé Bore (BDD). Une limite de détection de 0.007ng/mL a été obtenue et l'immunocapteur a été testé sur des échantillons réels. Enfin, on a développé un aptacapteur basé sur le greffage d'un espaceur (PEG) sur la surface des microcellules BDD pour la quantification de la biotoxine OTA. Une limite de détection de 0,01ng/L a été obtenue et application à un échantillon réel (le riz) a été démontrée. Les résultats obtenus, basés sur des méthodes électrochimiques de détection (variation de l'impédance ou du courant d'une sonde redox) sont encourageantes en termes de sensibilité, limite de détection, reproductibilité et spécificité / The objective of the research work was to the development of modified electrode materials for biosensor application. The work was devided into three parts: electrografting of diazonium salt for immunosensor application, electroadressing of antibodies and electrodeposition of PEG spacer for aptasensor application. In the first part of this work, the modification of gold surfaces with nitrobenzene diazonium cation was investigated in order to develop an immunosensors for the detection of Staphylococcus aureus. A detection limit of 10 CFU/mL has been obtained. The second part was focused on the electrically addressable deposition of diazonium functionalized antibodies on boron-doped diamond (BDD) microcells for the detection of OTA. A detection limit of 0.007ng/mL has been obtained and the immunosensor was tested on real samples. Finally, we developed an amperometric aptasensor based on electrochemical grafting of a PEG-COOH spacer on a BDD microcell for the detection of OTA biotoxin. A detection limit of 0.01 ng/L has been obtained and application to a real sample (rice) has been demonstrated. The amperometric and impedimetric techniques used in this work lead to promising results in terms of sensitivity, specificity and reproductibility

[pt] O pH constitui um dos parâmetros de controle de qualidade do etanol combustível, sendo estabelecido pela norma brasileira ABNT NBR 10891, cujo escopo é específico para etanol hidratado combustível, e pela norma americana ASTM D 6423, a qual o foco é o etanol anidro combustível. Neste contexto, o presente estudo apresenta uma análise crítica à composição dos eletrodos utilizados pelos diferentes sistemas de medições para pH de etanol, devido à presença de água na composição do eletrodo de vidro. Com isso, o objetivo do presente estudo consistiu em uma proposta de um novo sistema para medição de pH de etanol hidratado combustível, o qual foi o único solvente utilizado, empregando como referência indicadores ácido-base. Por meio do planejamento de experimentos Box-Behnken foi possível determinar a condição otimizada esperada para o novo sistema de medição, o qual foi comparado com os sistemas propostos pelos referenciais normativos e posteriormente com o intervalo de pH definido pelos indicadores. Os resultados revelaram que os valores de pH obtidos pelos diferentes sistemas utilizados, incluindo o proposto pelo presente estudo, são estatisticamente diferentes entre si, e que somente os valores obtidos pelo novo sistema de medição se adequa à faixa de pH encontrada pelos indicadores. O eletrodo otimizado apresentou uma sensibilidade de resposta adequada à equação de Nernst, tendo um comportamento operacional adequado ao novo sistema de medição proposto pelo presente estudo. / [en] The pH is one of the quality control parameters of fuel ethanol, established by the Brazilian standard ABNT NBR 10891, whose scope is specific for hydrated fuel ethanol, and by the American standard ASTM D 6423, which focuses on anhydrous ethanol fuel. In this context, the present study presents a critical analysis of the composition of the electrodes used by the different measurement systems for ethanol pH, due to the presence of water in the composition of the glass electrode. Thus, the objective of the present study was to propose a new system for measuring the pH of hydrated fuel ethanol, which was the only solvent used, using acid-base indicators as a reference. Box-Behnken Design made possible to determine the optimal condition expected for the new measurement system, which was compared with the systems proposed by the normative references and later with the pH range defined by the indicators. The results revealed that the pH values obtained by the different systems used, including the one proposed by the present study, are statistically different from each other, and that only the values obtained by the new measurement system are suitable for the pH range found by the indicators. The optimized electrode presented an adequate response sensitivity to the Nernst equation, having an operational behavior adequate to the new measurement system proposed by the present study.

Nos últimos anos, materiais baseados em grafeno têm atraído grande interesse na área eletroquímica devido às suas excelentes propriedades eletrônicas. Neste trabalho, apresentamos a obtenção de óxido de grafeno reduzido utilizando métodos eletroquímicos. A redução eletroquímica do óxido de grafeno (OG) foi realizada na superfície de um eletrodo de carbono vítreo (ECV) utilizando voltametria cíclica. O óxido de grafeno reduzido eletroquimicamente (OG-RE) foi caracterizado utilizando espectroscopia Raman, microscopia eletrônica de varredura (MEV), microscopia de força atômica (MFA), espectroscopia de fotoelétrons excitados por raios-X (XPS) e espectroscopia de impedância eletroquímica. A relação ID/IG obtida através dos espectros Raman do OG e do OG-RE foram de 0,98 e 1,15, respectivamente, indicando que o processo de redução resultou em uma maior desorganização estrutural. A espectroscopia de fotoelétrons de raios-X mostrou que a proporção entre C e O no OG foi de 45,7% e, que após a redução eletroquímica essa relação diminuiu para 38,5%. O eletrodo modificado com OG-RE foi empregado para quantificação de furosemida (FUR) em amostras farmacêuticas utilizando voltametria de pulso diferencial e análise por injeção em fluxo com detecção amperométrica. Os limites de detecção e quantificação calculados para o método proposto foram de 0,35 e 1,18 µmol L-1, respectivamente. Visando à aplicação em amostras de interesse clínico, fabricou-se um sensor descartável e de baixo custo para a detecção de FUR utilizando papel sulfite pintado com lápis de desenho e ativado por laser de CO2. Os estudos voltamétricos utilizando o [Ru(NH3)6]Cl3 mostraram que o transporte de massa neste dispositivo foi governado por difusão e que o tratamento com laser diminui a resistência a transferência de carga, assim como resultou em um menor problema relacionado ao envenenamento da superfície do eletrodo / In recent years, graphene-based materials have attracted great interest in the area of electrochemistry due to its excellent electronic properties. In this work, we present the production of reduced graphene oxide using electrochemical methods. The electrochemical reduction of graphene oxide (GO) was carried out on the surface of a glassy carbon electrode (GCE) using the cyclic voltammetry technique. Electrochemically reduced graphene oxide (ER-GO) was characterized using Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), Xray excited photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). ID / IG ratio obtained through Raman spectra of GO and ER-GO were 0.98 and 1.15, respectively, indicating that the reduction process resulted in greater structural disorganization. XPS showed that the ratio between C and O in the GO was 45.7% and that after electrochemical reduction this ratio decreased to 38.5%. The ER-GO modified electrode was used as a sensor for furosemide (FUR) in pharmaceutical samples using the techniques of differential pulse voltammetry and flow injection analysis with amperometric detection. The limits of detection and quantification for the proposed method were 0.35 and 1.18 µmol L-1, respectively. Aiming to the application in clinical samples a disposable, low-cost paper-based sensor for the detection of FUR was fabricated using office paper painted with drawing pencil and activated by CO2 laser. Voltammetric studies using [Ru(NH3)6]Cl3 have shown that mass transport in this device was controlled by diffusion and the laser decreases resistance to charge transfer, as well as, avoided the problem with electrode surface poisoning

Made available in DSpace on 2017-07-24T19:37:55Z (GMT). No. of bitstreams: 1 Silvane Machado.pdf: 3592159 bytes, checksum: eb40ce07788b3e465452f6695e411555 (MD5) Previous issue date: 2016-08-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this work the ruthenium arene complex of general formula [Ru(6-p-cymene)(ampy)Cl]+ (Ru-ampy) containing the 2-aminomethylpiridine ligand was obtained from the cleavage of the chloride bridges of the [Ru(6-p-cimeno)(-Cl)Cl]2 complex. The structure of the Ru-ampy was elucidated by X-ray diffraction, which was compared to the optimized structure DFT theoretical level and there was distinct values of length of Ru-N bond, proving that Ru is coordinated to the ampy ligand by atom of nitrogen N-pyridine ring as the amine nitrogen atom. Experimental electronic spectra, and the theoretical spectra obtained by TDDFT method performed in various solvents showed a small displacement of the bands due to the solvation caused by the nature of the solvent to the complex. From the composition analysis of the orbital, bands observed at 320 and 450 nm were attributed to metal charge transfer transitions to the ligand. In the vibrational spectra observed a shift of the bands of ampy and arene ligands for smaller wavenumber values when they are coordinated to pyridine complex, which results corroborated with the NMR 1H results where there was an increase in shielding of the hydrogen of the p-cymene of the complex Ru-ampy compared with the proton of the precursor. In the electrochemical behavior of Ru-ampy obtained by cyclic voltammetry in CH3CN it was found that a chemical step occurs with the arene labilization and replacement of the solvent after the oxidation of [Ru(6-p-cimeno)(ampy)Cl]+ to [Ru(6-p-cimeno)(ampy)Cl]2+ at 1.5 V, forming the species [Ru(CH3CN)3(ampy)Cl]2+. In order to explore the electrochemical potentiality of Ru-ampy, this was used as a ceramic carbon electrode modifier (CCE-Ru). The cyclic voltammogram of CCE-Ru in Britton-Robinson buffer (pH 7.0) showed only an almost reversible process with oxidation and reduction peaks at 0.39 and 0.35 V vs. Ag/AgCl, respectively, characterized by diffusion process on the electrode surface. With instrumental parameters square wave voltammetry (SWV) optimized (f = 20 s-1, a = 80 mV, ΔEs= 1 mV) analytical curves were constructed in the presence of paracetamol in the concentration intervals 1.99x10-6 - 3.10 x10-5 mol L-1 (R = 0.997), the values detection limit and quantification limit obtained, 1.94 x 10-6 and 5.83 x 10-7mol L-1 respectively are similar to electrodes reported in literature. The proposed method was successfully applied to determination of paracetamol in commercial pharmaceutical formulations (tablets and oral solution), the obtained results are in good agreement with the standard UV-Vis method at a 95% confidence level. / Neste trabalho o complexo de rutênio-areno coordenado ao ligante 2-aminomeltipiridina de fórmula [Ru(6-p-cimeno)(ampy)Cl]PF6 (Ru-ampy) foi obtido a partir da clivagem das pontes do clorido do complexo binuclear [Ru(6-p-cimeno)(-Cl)Cl]2. A estrutura do Ru-ampy foi elucidada por técnica de difração de raios X e comparada à estrutura otimizada em nível da teoria DFT. A combinação dsses resultados comprova a coordenação do ampy ao Ru pelo átomo de nitrogênio do anel N-piridínico e amínico. Os espectros eletrônicos experimentais e teóricos obtidos por método TDDFT, realizados em diferentes solventes, apresentaram um deslocamento das bandas devido à solvatação causada pela natureza do solvente ao complexo. A partir da análise de composição dos orbitais, as bandas observadas foram atribuídas à transição intraligante e transferência de carga do metal para o ligante. Nos espectros vibracionais constatou-se um deslocamento das bandas do ligante ampy e areno deslocam para menores valores de número de onda em relação aos ligantes coordenados. Este resultado corrobora com o aumento da blindagem dos átomo de hidrogênio do 6-p-cimeno em comparação com os prótons do complexo precursor observado por RMN de 1H. No estudo eletroquímico do Ru-ampy obtido por voltametria cíclica em CH3CN constatou-se que uma etapa química ocorre com a labilização do areno e substituição do solvente após a oxidação do [Ru(6-p-cimeno)(ampy)Cl]+ a [Ru(6-p-cimeno)(ampy)Cl]2+ em 1,57 V, formando a espécie [Ru(CH3CN)3(ampy)Cl]2+. O Ru-ampy foi utilizado como modificador de eletrodo de carbono cerâmico (ECC-Ru) a fim de explorar sua potencialidade eletrocatalítica na determinação de paracetamol em tampão Britton–Robinson (pH 7,0). O ECC-Ru apresentou um processo quase-reversível com picos de oxidação e redução em 0,39 e 0,35 V vs. Ag/AgCl, respectivamente, caracterizados por processo difusional na superfície do eletrodo. Os parâmetros instrumentais da voltametria de onda quadrada (VOQ) foram otimizados (f = 20 s-1, a = 80 mV, ΔEs= 1 mV) e as curvas analíticas construídas na presença de paracetamol no intervalo de 1,99x10-6 a 3,10 x10-5 mol L-1 (R=0,997) apresentaram valores de limites de detecção e de quantificação de 5,83 x 10-7 mol L-1 e 1,94 x 10-6mol L-1, respectivamente. O ECC-Ru foi aplicado para determinação de paracetamol em diferentes amostras (comprimido e solução oral) por VOQ e quando comparados aos resultados obtidos pelo método farmacopeico (UV-Vis) não apresentam diferença significativa em um nível de confiança de 95%.

Nos últimos anos, materiais baseados em grafeno têm atraído grande interesse na área eletroquímica devido às suas excelentes propriedades eletrônicas. Neste trabalho, apresentamos a obtenção de óxido de grafeno reduzido utilizando métodos eletroquímicos. A redução eletroquímica do óxido de grafeno (OG) foi realizada na superfície de um eletrodo de carbono vítreo (ECV) utilizando voltametria cíclica. O óxido de grafeno reduzido eletroquimicamente (OG-RE) foi caracterizado utilizando espectroscopia Raman, microscopia eletrônica de varredura (MEV), microscopia de força atômica (MFA), espectroscopia de fotoelétrons excitados por raios-X (XPS) e espectroscopia de impedância eletroquímica. A relação ID/IG obtida através dos espectros Raman do OG e do OG-RE foram de 0,98 e 1,15, respectivamente, indicando que o processo de redução resultou em uma maior desorganização estrutural. A espectroscopia de fotoelétrons de raios-X mostrou que a proporção entre C e O no OG foi de 45,7% e, que após a redução eletroquímica essa relação diminuiu para 38,5%. O eletrodo modificado com OG-RE foi empregado para quantificação de furosemida (FUR) em amostras farmacêuticas utilizando voltametria de pulso diferencial e análise por injeção em fluxo com detecção amperométrica. Os limites de detecção e quantificação calculados para o método proposto foram de 0,35 e 1,18 µmol L-1, respectivamente. Visando à aplicação em amostras de interesse clínico, fabricou-se um sensor descartável e de baixo custo para a detecção de FUR utilizando papel sulfite pintado com lápis de desenho e ativado por laser de CO2. Os estudos voltamétricos utilizando o [Ru(NH3)6]Cl3 mostraram que o transporte de massa neste dispositivo foi governado por difusão e que o tratamento com laser diminui a resistência a transferência de carga, assim como resultou em um menor problema relacionado ao envenenamento da superfície do eletrodo / In recent years, graphene-based materials have attracted great interest in the area of electrochemistry due to its excellent electronic properties. In this work, we present the production of reduced graphene oxide using electrochemical methods. The electrochemical reduction of graphene oxide (GO) was carried out on the surface of a glassy carbon electrode (GCE) using the cyclic voltammetry technique. Electrochemically reduced graphene oxide (ER-GO) was characterized using Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), Xray excited photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). ID / IG ratio obtained through Raman spectra of GO and ER-GO were 0.98 and 1.15, respectively, indicating that the reduction process resulted in greater structural disorganization. XPS showed that the ratio between C and O in the GO was 45.7% and that after electrochemical reduction this ratio decreased to 38.5%. The ER-GO modified electrode was used as a sensor for furosemide (FUR) in pharmaceutical samples using the techniques of differential pulse voltammetry and flow injection analysis with amperometric detection. The limits of detection and quantification for the proposed method were 0.35 and 1.18 µmol L-1, respectively. Aiming to the application in clinical samples a disposable, low-cost paper-based sensor for the detection of FUR was fabricated using office paper painted with drawing pencil and activated by CO2 laser. Voltammetric studies using [Ru(NH3)6]Cl3 have shown that mass transport in this device was controlled by diffusion and the laser decreases resistance to charge transfer, as well as, avoided the problem with electrode surface poisoning

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No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Bruno_Regis_Lyrio_Ferraz.PDF: 3015137 bytes, checksum: d479e9335e2f200939b52075f9b84382 (MD5) Previous issue date: 2016 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Funda??o de Amparo a Pesquisa do Estado de Minas Gerais (FAPEMIG) / RESUMO Etionamida e pirazinamida s?o antibi?ticos ?teis no tratamento da tuberculose multirresistente. O presente trabalho descreve o desenvolvimento e valida??o de metodologias eletroanal?ticas para determina??o de etionamida e pirazinamida em formula??es farmac?uticas e em urina humana empregando um eletrodo de diamante dopado com boro e um eletrodo de carbono v?treo modificado comum filme de poli glicina. Durante o desenvolvimento de ambas as metodologias, a voltametria c?clica foi empregada para verificar a influ?ncia do pH, da velocidade de varredura e do eletr?lito suporte no comportamento eletroqu?mico de ambos os analitos, bem como foram calculados os n?meros de pr?tons e el?trons envolvidos em cada uma das rea??es eletroqu?micas. A voltametria de onda quadrada com os par?metros otimizados foi utilizada para construir curvas anal?ticas para a ETO e PZA. Para a ETO foi obtido um intervalo linear de 1,0 a 80,0 ?mol L?1, com LOD e LOQ iguais a 0,294 e 0,980 ?mol L?1, respectivamente. Para a PZA foi obtido um intervalo linear de 0,47 a 6,16 ?mol L?1, com LOD e LOQ iguais a 0,035 e 0,12 ?mol L?1, respectivamente. A precis?o foi avaliada pelo registro de voltamogramas no mesmo dia e em dias diferentes, obtendo-se desvios padr?es relativos, inferiores a 5,0% em ambos os m?todos. Os resultados dos estudos de interferentes mostraram que nenhuma das subst?ncias testadas interferiu de maneira significativa na determina??o de ambos os f?rmacos. Os m?todos desenvolvidos foram comparados estatisticamente com os protocolos oficiais da farmacopeia atrav?s do teste-t e do teste-F, e os resultados mostraram que os valores de t e F calculados foram menores do que os valores de t e F cr?ticos, indicando que n?o houve diferen?a estat?stica entre as m?dias. A exatid?o de ambos os m?todos foi avaliada tamb?m por estudos de adi??o e recupera??o, obtendo-se como resultados percentuais de recupera??o pr?ximos a 100% para ambos os m?todos. A valida??o das metodologias desenvolvidas foi realizada pela avalia??o dos par?metros anal?ticos como sensibilidade, seletividade, limite de detec??o, limite de quantifica??o, faixa linear, exatid?o e precis?o e os resultados obtidos foram satisfat?rios. Portanto, os m?todos desenvolvidos podem ser aplicados com sucesso na determina??o dos f?rmacos ETO e PZA em medicamentos e urina humana. / Disserta??o (Mestrado) ? Programa de P?s-gradua??o em Ci?ncias Farmac?uticas, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2016. / ABSTRACT Ethionamide and pyrazinamide antibiotics are useful in the treatment of multidrugresistant tuberculosis. This work describes the development and validation of electroanalytical methodologies for determination of ethionamide and pyrazinamide in pharmaceutical formulation and human urine using boron-doped diamond electrode and poly glycine modified glassy carbon electrode, respectively. During the development of both methodologies, cyclic voltammetry was used to investigate the influence of pH, scan rate and the supporting electrolyte on the electrochemical behavior of both analytes, as well as the numbers of protons and electrons involved in each of the electrochemical reactions were calculated. Square wave voltammetry with optimized parameters were used to construct standard curves for ETO and PZA. For ETO a linear range from 1.0 to 80.0 ?mol L?1 was obtained with LOD and LOQ equal to 0.294 and 0.980 ?mol L?1, respectively. For PZA a linear range from 0.47 to 6.16 ?mol L?1was obtained with LOD and LOQ equal to 0.035 and 0.12 ?mol L?1, respectively. The precision was evaluated by voltammograms record on the same day and on different days, obtaining relative standard deviation less than 5.0% in both methods. The results of interfering studies showed that none of the tested substance interferes significantly in the determination of both drugs. The developed methods were statistically compared with the pharmacopoeia official protocols through the t-test and F-test, and the results showed that the calculated t and F values were lower than the critical t and F values indicating that there was no statistical difference between the averages. The accuracy of both methods was also evaluated by addition and recovery studies, obtaining results as percentage recovery close to 100% for both methods. The validation of the developed methodologies was carried out by the evaluation of analytical parameters such as sensitivity, selectivity, detection limit, quantification limit, linear range, accuracy and precision and the obtained results were satisfactory. Therefore, the developed methods can be applied successfully in the determination of ETO and PZA drugs in pharmaceuticals and human urine.

Le travail de thèse est consacré au développement d'électrodes composites à base d'argiles naturelles et à leur caractérisation électrochimique à des fins analytiques, notamment pour le dosage de cations métalliques (Cu2+) et de quelques substances à visée thérapeutique. Le premier chapitre expérimental est consacré à une étude comparée des caractéristiques chimiques, structurales et physico-chimiques de deux argiles naturelles extraites sur deux sites en Roumanie. Il apparaît que l'argile de Valea Chioarului, de type montmorillonite, présente les propriétés les plus intéressantes avec une surface spécifique importante (190 m2/g). Le deuxième chapitre fait état d'une analyse prospective des deux argiles comme matériaux d'électrodes en utilisant un film composite argile/poly-électrolyte. Trois molécules d'intérêt pharmaceutique ont été choisies pour cible, l'acide ascorbique, la riboflavine et l'acétaminophène. Cette dernière molécule peut être détectée soit par oxydation directe, soit via une réaction électro-enzymatique avec la peroxydase de raifort. Les troisième et quatrième chapitres sont consacrés à l'utilisation d'argiles échangées par des cations ammonium pour la détection du cuivre. Ainsi, l'argile de Valea Chioarului a été échangée partiellement avec du tétrabutylammumium. La perméabilité des films d'organo-argile recouverts d'un film de cellulose a été étudiée en utilisant différentes sondes électro-actives de charge différentes, Ru(NH3)63+, [Fe(CN)6]3-, Fc(MeOH)2. Les conditions expérimentales ont été ensuite optimisées pour la détection du Cu(II) et Cd(II) avec ces électrodes modifiées en voltammétrie à vague carrée. Dans le dernier chapitre, une configuration originale d'électrode modifiée a été mise au point. Il s'agit d'électrodes composites argile-silice mésoporeuse préparée par électrodéposition en présence ou non d'un tensioactif, le cétyltriméthylammonium. La perméabilité des films a également été étudiée avec les mêmes molécules que précédemment. Il apparait que l'extraction du tensio-actif conduit à des films homogènes très poreux et stables qui présentent des propriétés d'accumulation du Cu(II) / The thesis is devoted to the development of composite electrodes based on natural clays and their electrochemical characterization for analytical purposes, in particular for the determination of metal cations (Cu2+) and some therapeutic substances. The first experimental chapter is devoted to a comparative study of the chemical, structural and physico-chemical properties of two natural clays extracted from two sites in Romania. It appears that Valea Chioarului clay, of montmorillonite type, has the most interesting properties with a high specific surface area (190 m2/g). The second chapter presents a prospective analysis of the two clays as electrode materials using a clay/polyelectrolyte composite film. Three target molecules of pharmaceutical interest have been selected: ascorbic acid, riboflavin, and acetaminophen. This last molecule can be detected either by direct oxidation or through an electro-enzymatic reaction with horseradish peroxidase. The third and fourth chapters are devoted to the use of clays exchanged by ammonium cations for copper detection. Thus, Valea Chioarului clay was partially exchanged with tétrabutylammumium. The permeability of the organoclay films coated with a cellulose membrane was studied by using different electroactive probes of different charging, Ru(NH3)63+, [Fe(CN)6]3-, Fc(MeOH)2. The experimental conditions were then optimized for the detection of Cu (II) and Cd (II) with the modified electrodes by square wave voltammetry. In the last chapter, an original modified electrode configuration was developed. This implies composite mesoporous silica-clay electrodes prepared by electrodeposition in the presence or absence of a surfactant, like cetyltrimethylammonium. The permeability of the films was also investigated with the above mentioned molecules. It appears that the extraction of the surfactant leads to very stable and homogeneous porous films that show Cu (II) accumulation properties

Submitted by GLÁUCIA TINOCO CORRÊA null (glauciacorrea_15@hotmail.com) on 2017-09-07T02:49:22Z No. of bitstreams: 1 tese versão online.pdf: 5660272 bytes, checksum: c8ac61b6a73153496fecaf76e1315c4d (MD5) / Approved for entry into archive by Monique Sasaki (sayumi_sasaki@hotmail.com) on 2017-09-11T20:12:56Z (GMT) No. of bitstreams: 1 correa_gt_dr_araiq.pdf: 5660272 bytes, checksum: c8ac61b6a73153496fecaf76e1315c4d (MD5) / Made available in DSpace on 2017-09-11T20:12:56Z (GMT). No. of bitstreams: 1 correa_gt_dr_araiq.pdf: 5660272 bytes, checksum: c8ac61b6a73153496fecaf76e1315c4d (MD5) Previous issue date: 2017-08-17 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Corantes de cabelo, provenientes principalmente da tintura comercial de cabelo em salões de beleza, quando não convenientemente descartados, podem gerar efluentes de difícil tratamento. Além disso, a análise de corante de cabelo em fios de cabelo tingidos, poderia favorecer informações úteis para análise forense. Em virtude de alto consumo de corantes de cabelo, que podem ser encontrados na forma de tinturas permanente, semipermantes e temporárias, com diferentes estruturas e comportamento físico-químico, a demanda por métodos analíticos sensíveis e robustos para sua quantificação é altamente pertinente. Diante disso, o presente trabalho descreve a construção de sensores eletroquímicos para quantificação de corantes de cabelo do tipo temporário, pois são classe de corantes facilmente removidos do cabelo e, consequentemente, podem ser liberados para o meio ambiente. O sensor eletroquímico consiste no desenvolvimento de um eletrodo compósito com partículas magnéticas modificadas como grupos carboxílicos (CFMP) para determinação dos corantes basic brown 16 (BB16), basic red 51 (BR51) e basic yellow 57 (BY57) em amostras de extratos de fios de cabelos, amostras comercias de tintura temporária, água de lavagem, amostras de água de rio e de torneira. Os três corantes apresentam grupos azos como cromóforos. No presente trabalho, investigou-se a oxidação de aminas e hidroxilas presentes como grupos auxocromos nos corantes. Os resultados mostraram que a oxidação do grupo funcional nos corantes sobre o eletrodo compósito modificados por grupos carboxílicos pode ocorrer em potenciais de 0,44 V, 0,86 V e 0,65, respectivamente para os corantes BB16, BR51 e BY57 e a corrente de pico aumenta significativamente em relação ao eletrodo sem modificação. A interação entre corante + CFMP foi comprovada por espectroscopia de UV/Vis e FTIR. Foram construídas curvas analíticas para os corantes BB16, BR51 e BY57, usando as condições otimizadas na técnica de voltametria de onda quadrada (VOQ): frequência de aplicação dos pulsos (f) = 30 s-1, amplitude de pulsos (a) = 50 mV e incremento de varredura (ΔEs) = 2 mV para os corantes. Relações lineares foram obtidas nos intervalos de 2,0 x 10-7 mol L-1 a 9,0 x 10-7 mol L-1, 1,5 x 10-6 mol L-1 a 5,5 x 10-5 mol L-1, 2,0 x 10-7 mol L-1 a 1,2 x 10-7 mol L-1 para os corantes BB16, BR51 e BY57, respectivamente. Foram obtidos limites de detecção de 1,01 x 10-8 mol L-1, 1,19 x 10-7 mol L-1 e 2,89 x 10-7 mol L-1 para os corantes BB16, BR51 e BY57, respectivamente. O método foi aplicado em amostras de extratos de fios de cabelo, água de lavagem, água de torneira e formulações comerciais. A determinação simultânea dos corantes BB16, BR51 e BY57 foi também proposto usando o método descrito e otimizado. O método foi aplicado em amostras de água de torneira e água de rio com recuperações de aproximadamente 100% e em amostra da tintura de cabelo comercial (COLOR EXPRESS (Vermelho intenso). O método eletroquímico foi comparado com o método de referência usando cromatografia líquida de alta eficiência com detector de arranjo de diodo (HPLC/DAD). / Hair dyes, mainly coming from commercial hair colorants in beauty salons, when not properly discarded, can generate effluents that are difficult to treat. In addition, hair dye analysis in dyed hair strands could be used as useful information for forensic analysis. Due to the high consumption of hair dyes, which can be found in the form of permanent, semipermanent and temporary dye, with different structures and physicochemical behavior, the demand for sensitive and robust analytical methods for their quantification is highly relevant. Therefore, the present work describes the construction of electrochemical sensors for the quantification of hair dyes of the temporary type, because they are class of dyes easily removed from the hair and, consequently, are released in great quantity for the environment. The electrochemical sensor consists of the development of a composite electrode using modified magnetic particles with carboxylic groups (CFMP) to determine the dyes basic brown 16 (BB16), basic red 51 (BR51), and basic yellow 57 (BY57) in samples of yarn extracts Hair samples, commercial samples of temporary tincture, wash water, samples of river water and tap water. The three dyes analyzed have azide groups as chromophores. In the present work, the oxidation of amines and hydroxyls present as auxochromic groups in the dyes was investigated. The results showed that the oxidation of the functional group in the dyes on the composite electrode modified by carboxylic groups can occur in Ea = 0.44 V, Ea = 0.86 V and Ea = 0.65, respectively for the dyes BB16, BR51, and BY57 and the peak current increases significantly with respect to the electrode without modification. The interaction between dye + CFMP was confirmed by UV/Vis and FTIR spectroscopy. Analytical curves for the BB16, BR51, and BY57 dyes were constructed using the optimized conditions in the square wave voltammetry (SWV) technique: pulse frequency (f) = 30 s-1, pulse amplitude (a) = 50 mV and scanning increment (ΔEs) = 2 mV for the dyes. Linear relationships were obtained at intervals of 2.0 x 10-7 mol L-1 to 9.0 x 10-7 mol L-1, 1.5 x 10-6 mol L-1 at 5.5 x 10-5 mol L-1, 2.0 x 10-7 mol L-1 to 1.2 x 10-7 mol L-1 for the dyes BB16, BR51, and BY57, in this order, using the SWV technique. Detection limits of 1.01 x 10-8 mol L-1, 1.19 x 10-7 mol L-1, 2.89 x 10-7 mol L-1 were obtained for the dyes BB16, BR51, and BY57, respectively. The method was applied to hair strands, wash water, tap water, and commercial formulation samples. The simultaneous determination of the dyes BB16, BR51, and BY57 was also proposed using the method described and optimized. The simultaneous determination of the dyes BB16, BR51 and, BY57 was also proposed using the method described and optimized. The method was applied to tap water and river water samples with approximately 100% recoveries and commercial hair dye sample (COLOR EXPRESS®). The electrochemical method was compared with the reference method using high performance liquid chromatography with diode arrangement detector (HPLC/DAD). / FAPESP: 2013/21542-6

Comme dans beaucoup de domaines, la sécurité dépend du développement de méthodes analytiques très sensibles et fiables pour pouvoir détecter des molécules dangereuses. C'est pourquoi il est important de développer des méthodes simples afin de diagnostiquer rapidement un composé dangereux dans notre environnement. Dans ce contexte, les techniques électrochimiques offrent une alternative intéressante puisqu'elles permettent d'atteindre de grandes sensibilités et une bonne sélectivité, elles sont peu coûteuses et facilement adaptables pour la création de dispositifs portables. Récemment, notre équipe a développé un nouveau concept basé sur de la voltammétrie par échantillonnage de courant sur un réseau d'électrodes (EASCV), lequel est compatible avec la miniaturisation. Ce système permet de renouveler la surface et la solution au voisinage de l'électrode pendant l'analyse. Le projet de cette thèse a été d'étendre l'application de cette technique à des méthodes électrochimiques utilisant une étape de préconcentration. Une première étude, appliquée à la détection du phénol, a permis de montrer que l'EASCV offre une solution intéressante pour diminuer les phénomènes de passivation ayant lieu pendant l'analyse. En effet, une étude expérimentale associée à une étude théorique a montré que si un temps d'échantillonnage court était appliqué, le phénomène de passivation pouvait être évité. Enfin, pour la première fois, il a été possible de coupler la voltammétrie par échantillonnage de courant à la redissolution anodique. Cette étude, appliquée à la détection du plomb, a permis de mettre en place une courbe d'étalonnage et d'obtenir une intensité élevée de courant, 300 fois plus importante qu'avec les techniques classiques de redissolution anodique. Les premiers essais pour adapter ce nouveau concept aux méthodes pulsés se sont également montrés très encourageants. Afin d'améliorer la sensibilité et la sélectivité du capteur, le réseau d'électrodes a été fonctionnalisé. La modification dépend de la nature de l'espèce cible. Ainsi des polymères à empreintes moléculaires (pour des molécules comme la mélamine) ou des ligands (pour des ions comme le plomb) ont été testés. Dans les deux cas, une méthode d'électrogreffage a été mise au point pour fonctionnaliser la surface. Les premiers résultats obtenus sont encourageants puisqu'une courbe courant-potentiel a pu être tracée montrant une sensibilité 10 fois plus grande pour le plomb que celle obtenue avec une préconcentration par électrodépôt. / As in many fields, safety is primarily based on the development of reliable and highly sensitive analytical methods to detect hazardous molecules. Therefore there is a need for developing simple methods for the diagnosis of harmful molecules in our environment. In this context, electrochemical detection systems seems very promising because they are highly sensitive, require short analysis time, are easy to implement and economic to fabricate. Moreover, our team has recently developed a new concept of device based on sampled-current voltammetry performed on an electrode array (EASCV) which is compatible with miniaturization and portability. The system allows the renewal of the electrode surface and of the analytical solution during the analysis. The present project addresses these issues and aims to extend it to methods involving a preconcentration step. A first study, for the detection of phenol, showed that EASCV offers a versatile solution to decrease fouling effect during the analysis. Indeed experimental and theoretical studies show that the renewable of electrode surface and of the solution in the vicinity of the electrode associated with the use of a short sampled time can avoid electrode fouling. For the first time, it was possible to combine sampled-current voltammetry with anodic stripping voltammetry. In this study, we were able to create a calibration curve, for the detection of lead, and we obtained current intensities 300 times higher than with usual linear stripping voltammetry.First attempts to adapt this new concept to pulse methods were promising.. To increase the sensitivity and selectivity of the sensor, the electrode array is chemically modified. The nature of this modification depends on the nature of the analyte. Thus, molecular imprinted polymer (for molecules) or macrocyclic ligands (for ions) are tested In both cases, an electrografting method is achieved to functionalize the surface. The first results are promising since a current-potential curve is obtained with a sensibility ten times higher than with a preconcentration by electrodeposition.

The main objective of this Diploma Thesis is studying the possibility of detection of nitro derivatives of aromatic hydrocarbons by using chemically modified working electrodes in electrochemical analysis. Compounds analyzed in this work were 1-nitronaphthalene and 6- nitrochrysene - these compounds were chosen on previous experience with surface modified working electrodes (the chemical/physical properties of these substances). All the analyses were performed by using differential pulse voltammetry (DPV) on hanging mercury drop electrode (HMDE) in classic three-electrode system. The original premise of chemical modification of electrode surface is the change of its selectivity towards different compounds - meaning the change of the electrochemical response. The modification agent used in this thesis is 1-octanethiol. Its thiol group offers great potential of strong interaction with the metal surface of the mercury electrode. Voltammetric responses of both compounds were recorded in acidic, neutral and basic solutions (pH=2, pH=7, pH=12) including the responses when the electrode surface was modified. Next objective was the optimization of the modification procedure itself (transferring of the mercury drop from one media to another without damaging or tearing it off from the capillary orifice)....