This research investigated the mechanism, kinetics and feasibility of nitrate, arsenate, and trichloroethylene inactivation on zerovalent iron (ZVI), mixed-valent iron oxides, and boron doped diamond film electrode surfaces, respectively. Nitrate ( ) is a common co-contaminant at sites remediated using permeable reactive barriers (PRBs). Therefore, understanding nitrate reactions with ZVI is important for understanding the performance of PRBs. This study investigated the reaction mechanisms of with ZVI under conditions relevant to groundwater treatment. Tafel analysis and electrochemical impedance spectroscopy were used to probe the surface reactions. Batch experiments were used to study the reaction rate of with freely corroding and cathodically protected iron wires. The removal kinetics for the air formed oxide (AFO) were 2.5 times slower than that of water formed oxide (WFO).This research also investigated the use of slowly corroding magnetite (Fe3O4) and wustite (FeO) as reactive adsorbent media for removing As(V) from potable water. Observed corrosion rates for mixed valent iron oxides were found to be 15 times slower than that of zerovalent iron under similar conditions. Electrochemical and batch and column experiments were performed to study the corrosion behavior and gain a deeper understanding on the effects of water chemistry and operating parameters, such as, empty bed contact times, influent arsenic concentrations, dissolved oxygen levels and solution pH values and other competing ions. Reaction products were analyzed by X-Ray diffraction and XPS to determine the fate of the arsenic.This research also investigated use of boron doped diamond film electrodes for reductive dechlorination of trichloroethylene (TCE). TCE reduction resulted in nearly stoichiometric production of acetate. Rates of TCE reduction were found to be independent of the electrode potential at potentials below -1 V with respect to the standard hydrogen electrode (SHE). However, at smaller overpotentials, rates of TCE reduction were dependent on the electrode potential. Short lived species analysis and density functional simulations indicate that TCE reduction may occur by formation of a surface complex between TCE and carbonyl groups present on the surface.

Este trabalho investigou a oxidação eletroquímica do ácido tânico em eletrodos do tipo Ânodo Dimensionalmente Estáveis (ADE) a base de SnO2 e IrO2 e eletrodos de Diamante Dopado com Boro (BDD). As eletrólises foram feitas em modo galvanostático em função de parâmetros como densidade de corrente e concentração de cloreto. A oxidação eletroquímica do ácido tânico foi capaz de promover a diminuição da concentração de fenóis totais, Carbono Orgânico Total (COT) e Demanda Química de oxigênio (DQO). Para os ADE os melhores resultados de remoção de Carbono Orgânico Total (COT) foram nas condições em que se utilizou 300 mg L-1 de cloreto e densidade de corrente de 25 mA cm-2. No entanto houve a formação de compostos organoclorados que não foram degradados com maiores tempo de reação. Para os eletrodos de BDD, obteve-se a remoção de aproximadamente 98% de COT após 10 horas de reação à 75 mA cm-2, na ausência de cloreto. Maiores remoções de COT são obtidas com o aumento da densidade de corrente. Eletrólises na presença de cloreto removeram quase 100% do COT em tempos menores de reação. Análises de compostos organohalogenados (AOX) mostraram que não houve a formação de compostos organoclorados. Menores densidades de corrente apresentaram maiores Eficiência de Corrente (EC) e menor Consumo de Energia (CE). As eletrólises na presença de cloro apresentaram melhores resultados de EC que na ausência do mesmo. A oxidação fotoeletroquímia do ácido tânico em eletrodos do tipo ADE de composição nominal Ti/ Sn0,7 Ir0,3 O2 também foi investigada nesse trabalho. O tratamento fotoeletroquímico foi realizado utilizando uma lâmpada de vapor de mercúrio de alta pressão de 125 W como fonte de irradiação. A variação da corrente não mostrou diferença significativa na oxidação do ácido tânico. A variação da concentração de cloreto no eletrólito suporte influenciou de forma acentuada a oxidação do ácido tânico. O tratamento fotoeletroquímico se mostrou mais eficiente na remoção de COT que os tratamentos eletroquímico e fotoquímico. No tratamento fotoeletroquímico ocorreu a formação de AOX no início da reação, no entanto com o passar do tempo esses compostos foram degradados. / This study investigated the electrochemical oxidation of tannic acid on electrodes of the Dimensionally Stable Anode (DSA) type based on SnO2 and IrO2 as well as on boron doped diamond (BDD) electrodes. The electrolyses were performed in the galvanostatic mode, as a function of such parameters as current density and chloride concentration. The electrochemical oxidation of tannic acid was able to promote the reduction of the concentration of total phenolics, total organic carbon (TOC), and chemical oxygen demand (COD). For the DSA the best results of Total Organic Carbon (TOC) removal were achieved at 300 ppm chloride and current density of 25 mA cm-2. However, organochlorine compounds were formed and were not degraded with increased reaction times. For the BDD electrodes, the removal of approximately 98% TOC was obtained after 10 hours of reaction at 75 mA cm-2, in the absence of chloride. Major TOC removals were obtained with increasing current density. Electrolyses in the presence of chloride removed almost 100% TOC in shorter reaction times. Analysis of organohalogen compounds (AOX) showed no formation of organochlorine compounds. Lower current densities led to higher current efficiency (CE) and lower Energy Consumption (EC). The electrolyses in the presence of chlorine produced better CE results than those performed in the absence of chlorine. The photoelectrochemical oxidation of tannic acid in ADE-type electrodes of nominal composition Ti / Sn0.9 Ir0.3 O2 was also investigated in this work. The photoelectrochemical treatment was performed using a high pressure mercury vapor lamp 125 W as the source of irradiation. The variation in current revealed no significant difference in the oxidation of tannic acid. The variation in chloride concentration in the electrolyte markedly influenced the oxidation of tannic acid. The photoelectrochemical treatment was more efficient for TOC removal than the electrochemical and photochemical treatments. Formation of AOX occurred at the beginning of the photoelectrochemical treatment, but over time these compounds were degraded.

Este trabalho investigou a oxidação eletroquímica do ácido tânico em eletrodos do tipo Ânodo Dimensionalmente Estáveis (ADE) a base de SnO2 e IrO2 e eletrodos de Diamante Dopado com Boro (BDD). As eletrólises foram feitas em modo galvanostático em função de parâmetros como densidade de corrente e concentração de cloreto. A oxidação eletroquímica do ácido tânico foi capaz de promover a diminuição da concentração de fenóis totais, Carbono Orgânico Total (COT) e Demanda Química de oxigênio (DQO). Para os ADE os melhores resultados de remoção de Carbono Orgânico Total (COT) foram nas condições em que se utilizou 300 mg L-1 de cloreto e densidade de corrente de 25 mA cm-2. No entanto houve a formação de compostos organoclorados que não foram degradados com maiores tempo de reação. Para os eletrodos de BDD, obteve-se a remoção de aproximadamente 98% de COT após 10 horas de reação à 75 mA cm-2, na ausência de cloreto. Maiores remoções de COT são obtidas com o aumento da densidade de corrente. Eletrólises na presença de cloreto removeram quase 100% do COT em tempos menores de reação. Análises de compostos organohalogenados (AOX) mostraram que não houve a formação de compostos organoclorados. Menores densidades de corrente apresentaram maiores Eficiência de Corrente (EC) e menor Consumo de Energia (CE). As eletrólises na presença de cloro apresentaram melhores resultados de EC que na ausência do mesmo. A oxidação fotoeletroquímia do ácido tânico em eletrodos do tipo ADE de composição nominal Ti/ Sn0,7 Ir0,3 O2 também foi investigada nesse trabalho. O tratamento fotoeletroquímico foi realizado utilizando uma lâmpada de vapor de mercúrio de alta pressão de 125 W como fonte de irradiação. A variação da corrente não mostrou diferença significativa na oxidação do ácido tânico. A variação da concentração de cloreto no eletrólito suporte influenciou de forma acentuada a oxidação do ácido tânico. O tratamento fotoeletroquímico se mostrou mais eficiente na remoção de COT que os tratamentos eletroquímico e fotoquímico. No tratamento fotoeletroquímico ocorreu a formação de AOX no início da reação, no entanto com o passar do tempo esses compostos foram degradados. / This study investigated the electrochemical oxidation of tannic acid on electrodes of the Dimensionally Stable Anode (DSA) type based on SnO2 and IrO2 as well as on boron doped diamond (BDD) electrodes. The electrolyses were performed in the galvanostatic mode, as a function of such parameters as current density and chloride concentration. The electrochemical oxidation of tannic acid was able to promote the reduction of the concentration of total phenolics, total organic carbon (TOC), and chemical oxygen demand (COD). For the DSA the best results of Total Organic Carbon (TOC) removal were achieved at 300 ppm chloride and current density of 25 mA cm-2. However, organochlorine compounds were formed and were not degraded with increased reaction times. For the BDD electrodes, the removal of approximately 98% TOC was obtained after 10 hours of reaction at 75 mA cm-2, in the absence of chloride. Major TOC removals were obtained with increasing current density. Electrolyses in the presence of chloride removed almost 100% TOC in shorter reaction times. Analysis of organohalogen compounds (AOX) showed no formation of organochlorine compounds. Lower current densities led to higher current efficiency (CE) and lower Energy Consumption (EC). The electrolyses in the presence of chlorine produced better CE results than those performed in the absence of chlorine. The photoelectrochemical oxidation of tannic acid in ADE-type electrodes of nominal composition Ti / Sn0.9 Ir0.3 O2 was also investigated in this work. The photoelectrochemical treatment was performed using a high pressure mercury vapor lamp 125 W as the source of irradiation. The variation in current revealed no significant difference in the oxidation of tannic acid. The variation in chloride concentration in the electrolyte markedly influenced the oxidation of tannic acid. The photoelectrochemical treatment was more efficient for TOC removal than the electrochemical and photochemical treatments. Formation of AOX occurred at the beginning of the photoelectrochemical treatment, but over time these compounds were degraded.

L'usage intensif de pesticides dans l'agriculture engendre une contamination sans précédent des eaux de surface et des nappes phréatiques. Les traitements classiques appliqués aux eaux usées contenant des produits organiques polluants sont basés sur la biodégradation ou sur des méthodes physiques de transfert de masse (décantation, filtration, adsorption des polluants sur du charbon actif) ou des procédés chimique tels que l'oxydation à l'ozone ou au chlore. Cependant, ces procédés demeurent inefficaces dans le cas de traitement des eaux contaminées par les polluants organiques persistants (POPs). Les procédés d'oxydation avancés sont mis en œuvre pour dégrader ou même minéraliser ces polluants. Ce travail a donc pour objectif de déterminer un protocole expérimental pour détruire efficacement les pesticides, produits chimiques largement utilisés dans l'agriculture au Maroc, tels que le monochloro-benzène, le 1,2-dichlorobenzène, l'acide 2,4,5-trichlorophénoxy-acétique, et l'imazalil en utilisant les procédés d'oxydation avancée électro-Fenton et oxydation anodique avec différentes anodes telles que BDD, Pt et DSA. Ainsi, nous avons trouvé que le taux de minéralisation par procédé électro-Fenton avec l'anode BDD était de 92%, 95%, 92% et 97%pour le monochloro-benzène, le 1,2-dichlorobenzène, l'acide 2,4,5-trichlorophénoxy-acétique, et l'imazalil, respectivement, après 4 h de traitement. Ces résultats confirment l'efficacité des procédés d'oxydation avancés électrochimiques dans le traitement des eaux polluées par des pesticides / The intensive use of pesticides in agriculture generates, nowadays, an unprecedented contamination of surface water and groundwater. Conventional treatments applied to waste water containing organic pollutants are based on biological treatments méthods or physical mass transfer methods (decantation, filtration, adsorption of the pollutants on activated carbon), chemical oxidation with ozone, chlorine, etc. However, these methods remain ineffective for the treatment of water polluted by persistent organic pollutants (POPs). Advanced oxidation processes are implemented to degrade and mineralize these pollutants. This PhD thesis work aims to establish an experimental protocol to degrade and mineralize pesticides, chemicals widely used in agriculture in Morocco, such as monochlorobenzene, 1,2-dichlorobenzene, 2,4,5-trichlorophenoxy-acetic acid , and imazalil using the electro-Fenton and anodic oxidation processes with DD Pt or DSA anodes. Thus, the rate of mineralization was 92%, 95%, 92% and 97% for the monochloro-benzene, the 1,2-dichlorobenzene, the 2,4,5-trichlorophenoxyacetic acid , and the imazalil, respectively, after 4 h treatment by electro-Fenton process. These results confirm the effectiveness of electrochemical advanced oxidation processes for treating water polluted by pesticides

<p>In electrochemical oxidation treatment of wastewater, the electrode material is an important parameter in optimizing oxidative electrochemical processes, since the mechanism and products of several anodic reactions are known to depend on the anode material. The electrochemical oxidation of benzaldehyde, nitrobenzene and m-cresol on bare boron-doped diamond (BDD) electrode was investigated. Cytochrome c was then electrochemically immobilsed onto the functionalized BDD electrode by cyclic voltammetry. Oxidation and reduction reaction mechanism of each flavonoid was studied. There was one oxidation and reduction peaks for quercitin and catechin respectively, and two oxidation and two reduction peaks for rutin. The cytochrome c modified BDD electrode showed good sensitivity for all three flavonoids and low detection limits i.e. 0.42 to 11.24 M as evaluated at oxidation and reduction peaks, respectively.</p>

<p>In electrochemical oxidation treatment of wastewater, the electrode material is an important parameter in optimizing oxidative electrochemical processes, since the mechanism and products of several anodic reactions are known to depend on the anode material. The electrochemical oxidation of benzaldehyde, nitrobenzene and m-cresol on bare boron-doped diamond (BDD) electrode was investigated. Cytochrome c was then electrochemically immobilsed onto the functionalized BDD electrode by cyclic voltammetry. Oxidation and reduction reaction mechanism of each flavonoid was studied. There was one oxidation and reduction peaks for quercitin and catechin respectively, and two oxidation and two reduction peaks for rutin. The cytochrome c modified BDD electrode showed good sensitivity for all three flavonoids and low detection limits i.e. 0.42 to 11.24 M as evaluated at oxidation and reduction peaks, respectively.</p>

L'usage intensif de pesticides dans l'agriculture engendre une contamination sans précédent des eaux de surface et des nappes phréatiques. Les traitements classiques appliqués aux eaux usées contenant des produits organiques polluants sont basés sur la biodégradation ou sur des méthodes physiques de transfert de masse (décantation, filtration, adsorption des polluants sur du charbon actif) ou des procédés chimique tels que l'oxydation à l'ozone ou au chlore. Cependant, ces procédés demeurent inefficaces dans le cas de traitement des eaux contaminées par les polluants organiques persistants (POPs). Les procédés d'oxydation avancés sont mis en œuvre pour dégrader ou même minéraliser ces polluants. Ce travail a donc pour objectif de déterminer un protocole expérimental pour détruire efficacement les pesticides, produits chimiques largement utilisés dans l'agriculture au Maroc, tels que le monochloro-benzène, le 1,2-dichlorobenzène, l'acide 2,4,5-trichlorophénoxy-acétique, et l'imazalil en utilisant les procédés d'oxydation avancée électro-Fenton et oxydation anodique avec différentes anodes telles que BDD, Pt et DSA. Ainsi, nous avons trouvé que le taux de minéralisation par procédé électro-Fenton avec l'anode BDD était de 92%, 95%, 92% et 97%pour le monochloro-benzène, le 1,2-dichlorobenzène, l'acide 2,4,5-trichlorophénoxy-acétique, et l'imazalil, respectivement, après 4 h de traitement. Ces résultats confirment l'efficacité des procédés d'oxydation avancés électrochimiques dans le traitement des eaux polluées par des pesticides / The intensive use of pesticides in agriculture generates, nowadays, an unprecedented contamination of surface water and groundwater. Conventional treatments applied to waste water containing organic pollutants are based on biological treatments méthods or physical mass transfer methods (decantation, filtration, adsorption of the pollutants on activated carbon), chemical oxidation with ozone, chlorine, etc. However, these methods remain ineffective for the treatment of water polluted by persistent organic pollutants (POPs). Advanced oxidation processes are implemented to degrade and mineralize these pollutants. This PhD thesis work aims to establish an experimental protocol to degrade and mineralize pesticides, chemicals widely used in agriculture in Morocco, such as monochlorobenzene, 1,2-dichlorobenzene, 2,4,5-trichlorophenoxy-acetic acid , and imazalil using the electro-Fenton and anodic oxidation processes with DD Pt or DSA anodes. Thus, the rate of mineralization was 92%, 95%, 92% and 97% for the monochloro-benzene, the 1,2-dichlorobenzene, the 2,4,5-trichlorophenoxyacetic acid , and the imazalil, respectively, after 4 h treatment by electro-Fenton process. These results confirm the effectiveness of electrochemical advanced oxidation processes for treating water polluted by pesticides

Magister Scientiae - MSc / In electrochemical oxidation treatment of wastewater, the electrode material is an important parameter in optimizing oxidative electrochemical processes, since the mechanism and products of several anodic reactions are known to depend on the anode material. The electrochemical oxidation of benzaldehyde, nitrobenzene and m-cresol on bare boron-doped diamond (BDD) electrode was investigated. Cytochrome c was then electrochemically immobilsed onto the functionalized BDD electrode by cyclic voltammetry. Oxidation and reduction reaction mechanism of each flavonoid was studied. There was one oxidation and reduction peaks for quercitin and catechin respectively, and two oxidation and two reduction peaks for rutin. The cytochrome c modified BDD electrode showed good sensitivity for all three flavonoids and low detection limits i.e. 0.42 to 11.24 M as evaluated at oxidation and reduction peaks, respectively. / South Africa

Fundação de Amparo a Pesquisa do Estado de Minas Gerais / The present thesis demonstrates, for the first time, the possibility of using of the internal standard method in FIA or BIA systems with amperometric detection. The method allows to obtain accurate results in the presence of fluctuations in the system parameters (injected volume, dispensing rate, ionic strength and accidental insertion of air bubbles) and in the presence of contamination and/or gradual passivation of the working electrode surface. Methods for determination of diclofenac (DCF) using FIA with amperometric detection and simultaneous determination of DCF and codeine (CO) by BIA with amperometric detection have also been developed. The internal standard method was implemented in the flow injection analysis with multiple pulse amperometric detection (FIA-MPA) system by applying a sequence of potential pulses of the working electrode as a function of time. The analyte (+0.80 V/300ms) and internal standard (-0.05 V/400ms) were detected selectively, one at each potential pulse. Significant improvements were obtained in the accuracy of the system when the results before and after normalization (using the internal standard method), were compared. The following errors were calculated, respectively, before and after normalization of the results using the internal standard method. Change in flow rate from 3.0 to 1.0 ml min-1 (-57% e < 1%); volume injection from 300 to 100 &#956;L (-63% and 3%); ionic strength from 0.60 to 0.77 mol L-1 (-44 and 0,2%) and before and after the introduction of air bubbles into the system (-9,6% and 1,7%). A significant improvement was also obtained in the correlation coefficient of the calibration curve in the presence of problems of passivation or contamination of the working electrode. The correlation coefficient was calculated, respectively, as 0,975 and 0,998, before and after the normalization of the results by the IS method. The internal standard method was also applied to correct errors derived from the injection procedure (dispensing rate and injected volume) in batch injection analysis systems (BIA) with amperometric detection when disposable syringes were used. The results obtained before and after normalization of the results by the IS method were the following, respectively: repeatability test (RSD = 6.4 and 1.8%; n = 8), correlation coefficients (R=0.954 and 0.997) and errors obtained in analysis of synthetic samples (E = 9.4 ± 1.5 and 3.5 ± 0.7%; n = 8). The determination of DCF by FIA-MPA was implemented by applying two potential pulses to the BDD electrode using H2SO4 0.1 mol L-1 as supporting electrolyte: (i) + 1.2 V / 50 ms for oxidation and quantification of DCF, and (ii) 0.0 V / 50 ms for constant electrochemical cleaning of the electrode surface. The system showed good stability (RSD = 1.0%, n = 10) and high analytical frequency (135 injections h-1). The method showed a linear response between 5 and 50 &#956;mol L-1 and the detection and quantification limits were as 0.14 and 0.46 mmol L-1, respectively. The proposed method was applied to determine of DCF in pharmaceutical formulations and the obtained results were similar to those obtained by HPLC with a confidence level of 95%. The simultaneous determination of DCF and CO was performed using the following potential pulses: (i) +1.1 V / 50 ms: oxidation and quantification of DCF; (ii) +1.4 V / 50 ms: simultaneous oxidation of DCF and CO, (iii) 0.0 V / 200 ms: for constant electrochemical cleaning of the BDD electrode. The oxidation current from CO was obtained by the difference between currents detected at 1.4 and 1.1 V by using a correction factor. The system showed good stability (RSD = 0.9% and 1.1 for DCF and CO respectively, n = 10) and high analytical frequency (~ 300 injections h-1). The method showed a linear response between 10 and 50 &#956;mol L-1 for DCF and 7.1 and 35.7 &#956;mol L-1 for CO. The LQ and LD were calculated, respectively, at 1.1 and 3.7 &#956;mol L-1, for DCF and 1.0 and 3.3 mol L-1 for CO. The proposed method was applied for simultaneous determination of DCF and CO in pharmaceutical formulations and the obtained results were similar to those obtained by HPLC with a confidence level of 95%. Keywords: Multiple pulse amperometry, FIA, BIA, internal standard, simultaneous analysis, boron doped diamond (BDD), codeine, diclofenac. / Esta tese apresenta, pela primeira vez, a possibilidade de usar o método do padrão interno em sistemas FIA ou BIA com detecção amperométrica. O método permite a obtenção de resultados precisos na presença de flutuações em parâmetros dos sistemas (volume injetado, velocidade de injeção, força iônica e inserção acidental de bolhas de ar) e na presença de contaminação e/ou passivação gradual do eletrodo de trabalho. Métodos para determinação de diclofenaco (DCF) usando FIA com detecção amperométrica e simultânea de DCF e codeína (CO) por BIA com detecção amperométrica também foram desenvolvidos. O método do padrão interno foi implementado no sistema de análise por injeção em fluxo com detecção por amperometria de múltiplos pulsos (FIA-MPA) mediante a aplicação de uma sequência de pulsos de potenciais ao eletrodo de trabalho em função do tempo. O analito (+0,80 V/300ms) e o padrão interno (-0,05 V/400ms) foram detectados seletivamente, um em cada pulso de potencial. Melhoras significativas foram obtidas na precisão do método quando os resultados obtidos antes e após a normalização (usando o método do padrão interno) foram comparados. As seguintes variações foram calculadas, respectivamente, antes e após a normalização dos resultados usando o método do padrão interno. Variação na velocidade de vazão de 3,0 para 1,0 mL min-1 (-57% e < 1%); no volume de injeção de 300 para 100 &#956;L (-63% e 3%); força iônica de 0,60 para 0,77 mol L-1 (-44 e 0,2%) e antes e após a inserção de bolhas de ar no sistema (-9,6% e 1,7%). Uma melhora significativa também foi obtida no coeficiente de correlação da curva de calibração na presença de problemas de passivação ou contaminação do eletrodo de trabalho. O coeficiente de correlação foi calculado, respectivamente, em 0,975 e 0,998, antes e após a normalização dos resultados pelo método do PI. O método do padrão interno também foi aplicado para corrigir erros em sistemas de análise por injeção em batelada (BIA) com detecção amperométrica provenientes do procedimento de injeção (velocidade de injeção e volume injetado) quando seringas descartáveis foram utilizadas. Os resultados obtidos antes e após a normalização dos resultados pelo método do PI foram os seguintes, respectivamente: estudo de repetibilidade (DPR=6,4 e 1,8%; n = 8), coeficientes de correlação (R=0,954 e 0,997) e erros obtidos na análise de amostras sintéticas (9,4 ± 1,5% e 3,5 ± 0,7; n = 8). A determinação de DCF por FIA-MPA foi implementada através da aplicação de dois pulsos de potenciais ao eletrodo de BDD em meio de H2SO4 0,1 mol L-1 como eletrólito suporte: (i) +1,2 V / 50 ms para oxidação e quantificação do DCF e, (ii) 0,0 V / 50 ms para constante limpeza eletroquímica do eletrodo de trabalho. O sistema apresentou boa estabilidade (RSD = 1,0%; n=10) e elevada frequência analítica (135 injeções h-1). O método apresentou resposta linear entre 5 e 50 &#956;mol L-1 e os limites de detecção e quantificação foram calculados em 0,14 e 0,46 &#956;mol L-1, respectivamente. O método proposto foi aplicado na determinação de DCF em formulações farmacêuticas e os resultados obtidos foram similares ao obtidos por HPLC a um nível de confiança de 95%. A determinação simultânea de DCF e CO foi realizada usando os seguintes pulsos de potenciais: (i) +1,1 V / 50 ms: oxidação e quantificação de DCF; (ii) +1,4 V / 50 ms: para oxidação simultânea de DCF e CO; (iii) 0,0 V / 200 ms: para constante limpeza eletroquímica do eletrodo de BDD. A corrente de oxidação da CO foi obtida pela subtração entre as correntes detectadas em 1,4 e 1,1 V mediante uso de um fator de correção. O sistema apresentou boa estabilidade (RSD= 1,1 e 0,9% para DCF e CO, respectivamente, n=10) e elevada frequência analítica (~300 injeções h-1). O método apresentou resposta linear entre 10 e 50 &#956;mol L-1 para o DCF e entre 7,1 e 35,7 &#956;mol L-1 para CO. O LD e o LQ foram calculados, respectivamente, em 1,1 e 3,7 &#956;mol L-1, para DCF e 1,0 e 3,3 &#956;mol L-1 para CO. O método proposto foi aplicado na determinação simultânea de DCF e CO em formulações farmacêuticas e os resultados obtidos foram similares ao obtidos por HPLC a um nível de confiança de 95%. / Doutor em Química

In this work, an electrochemical method based on a cyt c biosensor has been developed, for the detection of selected arsenic and cyanide compounds. Boron Doped Diamond (BDD) electrode was used as a transducer, onto which cyt c was immobilised and used for direct determination of Prussian blue, potassium cyanide and arsenic trioxide by inhibition mechanism. The sensitivity as calculated from cyclic voltammetry (CV) and square wave voltammetry (SWV), for each analyte in phosphate buffer (pH= 7) was found to be (1.087- 4.488 ×10-9 M) and the detection limits ranging from 0.0043- 9.1 μM. These values represent a big improvement over the current Environmental Protection Agency (EPA) and World Health Organisation (WHO) guidelines.