Devido à alta toxicidade do mercúrio, os eletrodos contendo este metal vêm sendo substituídos por eletrodos modificados, dentre eles o filme de bismuto (f-Bi) tem demonstrado ser uma boa alternativa, pois apresentam comportamento e desempenho semelhante aos eletrodos de mercúrio, além de baixa toxicidade. A fim de se determinar os metais Cd2+ e Pb2+ em amostras de água do Rio Tietê, um eletrodo de f-Bi depositado de forma ex situ foi desenvolvido. As condições para a formação do f-Bi foram otimizadas e as melhores condições foram alcançadas utilizando uma solução de tampão acetato 0,2 mol L-1 pH 4,5 contendo 1,0x10-3 mol L-1 de Bi3+, aplicando um potencial de deposição de -0,50 V por 200 s. A determinação dos metais foi realizada através da voltametria de onda quadrada de redissolução anódica (SWASV - do inglês Square Wave Anodic Stripping Voltammetry), seus parâmetros foram otimizados e as melhores condições encontradas foram: frequência de 100 Hz; amplitude de pulso de 20 mV; step potential de 1 mV; potencial de pré-concentração de -0,925 V e tempo de pré- concentração de 450 s. Após a otimização dos parâmetros da SWASV foi construída uma curva analítica para os íons Cd2+ e Pb2+ na faixa de concentração de 5,0x10-8 a 3,0x10-6 mol L-1. As curvas analíticas apresentaram um aumento linear da corrente de pico em função da concentração dos metais com limite de detecção de 1,21 x10-7 e 1,13 x10-7 mol L-1 para o Cd e Pb, respectivamente. O método desenvolvido foi aplicado em amostras de água do rio Tietê e o f-Bi detectou Pb em concentração na ordem de 10-8 mol L-1. / Since Mercury is highly toxic, electrodes made with metal have been replaced by modified electrodes, among with bismuth film electrodes (f-Bi), and these latter ones have shown to be a good alternative, because they present both behavior and performance similar to the mercury electrodes, along with low toxicity. In order to determine Cd2+ and Pb2+ in water samples from the Tietê River, an f-Bi electrode laid up ex situ was developed. The conditions for the f-Bi formation were optimized and the best conditions were reached by using a solution of 0,2 mol L-1 acetate buffer with pH 4,5 containing 1,0 x10-3 mol L-1 of Bi3+, applying a deposition potential of -0,50 V for 200 s. Determinations of the metals was done by the square wave voltammetry anodic stripping voltammetry technique (SWASV), its parameters were optimized and the best conditions found were: 100 Hz frequency; 20 mV pulse amplitude; 1 mV step potential; -0,925 V pre-concentration potential and 450 s pre-concentration time. After the optimization of the technique an analytical curve was built with the addition of Cd2+ e Pb2+ metals in the concentration range between 5,0 x10-8 and 3,0 x10-6 mol L-1. The analytical curves showed a linear increase for the peak current in function of the concentration of the metals with detection limit of 1,21 x10-7 e 1,13 x10-7 mol L-1 for Cd and Pb, respectively. The developed method was applied in water samples from the Tietê River and the f-Bi detected Pb in a concentration of 10-8 mol L-1 order.

Devido à alta toxicidade do mercúrio, os eletrodos contendo este metal vêm sendo substituídos por eletrodos modificados, dentre eles o filme de bismuto (f-Bi) tem demonstrado ser uma boa alternativa, pois apresentam comportamento e desempenho semelhante aos eletrodos de mercúrio, além de baixa toxicidade. A fim de se determinar os metais Cd2+ e Pb2+ em amostras de água do Rio Tietê, um eletrodo de f-Bi depositado de forma ex situ foi desenvolvido. As condições para a formação do f-Bi foram otimizadas e as melhores condições foram alcançadas utilizando uma solução de tampão acetato 0,2 mol L-1 pH 4,5 contendo 1,0x10-3 mol L-1 de Bi3+, aplicando um potencial de deposição de -0,50 V por 200 s. A determinação dos metais foi realizada através da voltametria de onda quadrada de redissolução anódica (SWASV - do inglês Square Wave Anodic Stripping Voltammetry), seus parâmetros foram otimizados e as melhores condições encontradas foram: frequência de 100 Hz; amplitude de pulso de 20 mV; step potential de 1 mV; potencial de pré-concentração de -0,925 V e tempo de pré- concentração de 450 s. Após a otimização dos parâmetros da SWASV foi construída uma curva analítica para os íons Cd2+ e Pb2+ na faixa de concentração de 5,0x10-8 a 3,0x10-6 mol L-1. As curvas analíticas apresentaram um aumento linear da corrente de pico em função da concentração dos metais com limite de detecção de 1,21 x10-7 e 1,13 x10-7 mol L-1 para o Cd e Pb, respectivamente. O método desenvolvido foi aplicado em amostras de água do rio Tietê e o f-Bi detectou Pb em concentração na ordem de 10-8 mol L-1. / Since Mercury is highly toxic, electrodes made with metal have been replaced by modified electrodes, among with bismuth film electrodes (f-Bi), and these latter ones have shown to be a good alternative, because they present both behavior and performance similar to the mercury electrodes, along with low toxicity. In order to determine Cd2+ and Pb2+ in water samples from the Tietê River, an f-Bi electrode laid up ex situ was developed. The conditions for the f-Bi formation were optimized and the best conditions were reached by using a solution of 0,2 mol L-1 acetate buffer with pH 4,5 containing 1,0 x10-3 mol L-1 of Bi3+, applying a deposition potential of -0,50 V for 200 s. Determinations of the metals was done by the square wave voltammetry anodic stripping voltammetry technique (SWASV), its parameters were optimized and the best conditions found were: 100 Hz frequency; 20 mV pulse amplitude; 1 mV step potential; -0,925 V pre-concentration potential and 450 s pre-concentration time. After the optimization of the technique an analytical curve was built with the addition of Cd2+ e Pb2+ metals in the concentration range between 5,0 x10-8 and 3,0 x10-6 mol L-1. The analytical curves showed a linear increase for the peak current in function of the concentration of the metals with detection limit of 1,21 x10-7 e 1,13 x10-7 mol L-1 for Cd and Pb, respectively. The developed method was applied in water samples from the Tietê River and the f-Bi detected Pb in a concentration of 10-8 mol L-1 order.

<p>Coeliac disease (CD) is a gluten intolerance condition that results in the flattening of the villi, which line the bowel. It is the most common cause of malabsorption of food nutrients. This inability to absorb sufficient levels of nutrients causes many of the common symptoms experienced by CD patients. Some of the symptoms, which lead to an increase in mortality rate, include chronic diarrhea, fatigue, iron-deficient anemia and osteoporosis. People with CD have higher than normal levels of certain antibodies in their blood. Thus, the concentration of anti-transglutaminase antibody (anti-tTG) in human sera is an important analytical marker for the diagnosis of CD. An immunosensor is a type of biosensor that has an antigen or antibody fragment as its biological recognition component. The specificity of the molecular recognition of antigens by antibodies to form a stable complex is the basis of immunosensor technology. In this work, overoxidized polypyrrole (OvoxPpy) was electrosynthesized as a noval sensor platform on a glassy carbon electrode (GCE). The OvoxPpy was then doped with gold-nanoparticles (GNP) by electrodeposition using cyclic voltammetry to form GNP|OvoxPpy||GCE electrode system. Morphology and size of the GNP|OvoxPpy||GCE nanocomposite were determined using scanning electron microscopy. The electrochemical immunosensor for anti-tTG antibodies was prepared by immobilizing transglutaminase antigen (tTG-antigen) onto the GNP|OvoxPpy||GCE by drop coating and allowed to incubate for 2 hrs. The electrochemical characterization of the nanocomposite platform and immunosensor were studied by voltammetry and electrochemical impedance spectroscopy (EIS)...</p>

<p>In this study two medicinal plant species, namely Galenia africana and Elytropapus rhinocerotis, the former belonging to the family Aizoceae and the latter belonging to the family Asteraceae, have been investigated and different compounds isolated and characterized. Both species are important plants used in traditional medicine in Africa and particularly in South Africa. Flavanoids are secondary metabolites found in plants. They have a protective function against UV radiation and have a defence against invading illnesses due to their important antioxidant activity. Much of the food we eat and some beverages we drink contain flavonoids. The aim of this study was to investigate the electrochemistry of flavanoids isolated from these species.</p>

This study reports the synthesis of graphene by oxidizing graphite to graphite oxide using H2SO4 and KMnO4 and reducing graphene oxide to graphene by using NaBH4. Graphene was then characterized using FT-IR, TEM, AFM, XRD, Raman spectroscopy and solid state NMR. Nafion-Graphene in combination with a mercury film electrode, bismuth film electrode and antimony film electrode was used as a sensing platform for trace metal analysis in 0.1 M acetate buffer (pH 4.6) at 120 s deposition time, using square-wave anodic stripping voltammetry (SWASV). Detection limits were calculated using 3σblank/slope. For practical applications recovery studies was done by spiking test samples with known concentrations of metal ions and comparing the results to inductively coupled plasma mass spectrometry (ICPMS). This was then followed by real sample analyses.

The main objective of this work was to develop simple and sensitive electrochemical sensors for the detection of bisphenol A. To investigate the electrochemical behavior of BPA on a bare glassy carbon electrode. To apply the developed biosensor for the determination BPA by differential pulse voltammetry, electrochemical impedance spectrometry, square wave voltammetry and steady-state amperometry. To characterize the synthesized PDMA-PSS by cyclic voltammetry (CV), UV-Vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM).

A novel cyclopentadienylruthenium(II) thiolato Schiff base, [Ru(SC6H4NC(H)C6H4OCH2CH2SMe)(&eta / 5-C2H5]2 was synthesized and deposited as a selfassembled monolayer (SAM) on a gold electrode. Effective electronic communication between the Ru(II) centers and the gold electrode was established by electrostatically cycling the Shiff base-doped gold electrode in 0.1 M NaOH from -200 mV to +600 mV. The SAMmodified gold electrode (Au/SAM) exhibited quasi-reversible electrochemistry. The integrity of this electro-catalytic SAM, with respect to its ability to block and electro-catalyze certain Faradaic processes, was interrogated using Cyclic and Osteryoung Square Wave voltammetric experiments. The formal potential, E0', varied with pH to give a slope of about - 34 mV pH-1. The surface concentration, &Gamma / , of the ruthenium redox centers was found to be 1.591 x 10-11 mol cm-2. By electrostatically doping the Au/SAM/Horseradish peroxidase at an applied potential of +700 mV vs Ag/AgCl, a biosensor was produced for the amperometric analysis of hydrogen peroxide, cumene hydroperoxide and tert-butylhydroperoxide. The electrocatalytic-type biosensors displayed typical Michaelis-Menten kinetics with their limits of detection of 6.45 &mu / M, 6.92 &mu / M and 7.01 &mu / M for hydrogen peroxide, cumene hydroperoxide and tert-butylhydroperoxide respectively.

<p>In this study two medicinal plant species, namely Galenia africana and Elytropapus rhinocerotis, the former belonging to the family Aizoceae and the latter belonging to the family Asteraceae, have been investigated and different compounds isolated and characterized. Both species are important plants used in traditional medicine in Africa and particularly in South Africa. Flavanoids are secondary metabolites found in plants. They have a protective function against UV radiation and have a defence against invading illnesses due to their important antioxidant activity. Much of the food we eat and some beverages we drink contain flavonoids. The aim of this study was to investigate the electrochemistry of flavanoids isolated from these species.</p>

<p>Coeliac disease (CD) is a gluten intolerance condition that results in the flattening of the villi, which line the bowel. It is the most common cause of malabsorption of food nutrients. This inability to absorb sufficient levels of nutrients causes many of the common symptoms experienced by CD patients. Some of the symptoms, which lead to an increase in mortality rate, include chronic diarrhea, fatigue, iron-deficient anemia and osteoporosis. People with CD have higher than normal levels of certain antibodies in their blood. Thus, the concentration of anti-transglutaminase antibody (anti-tTG) in human sera is an important analytical marker for the diagnosis of CD. An immunosensor is a type of biosensor that has an antigen or antibody fragment as its biological recognition component. The specificity of the molecular recognition of antigens by antibodies to form a stable complex is the basis of immunosensor technology. In this work, overoxidized polypyrrole (OvoxPpy) was electrosynthesized as a noval sensor platform on a glassy carbon electrode (GCE). The OvoxPpy was then doped with gold-nanoparticles (GNP) by electrodeposition using cyclic voltammetry to form GNP|OvoxPpy||GCE electrode system. Morphology and size of the GNP|OvoxPpy||GCE nanocomposite were determined using scanning electron microscopy. The electrochemical immunosensor for anti-tTG antibodies was prepared by immobilizing transglutaminase antigen (tTG-antigen) onto the GNP|OvoxPpy||GCE by drop coating and allowed to incubate for 2 hrs. The electrochemical characterization of the nanocomposite platform and immunosensor were studied by voltammetry and electrochemical impedance spectroscopy (EIS)...</p>

A novel cyclopentadienylruthenium(II) thiolato Schiff base, [Ru(SC6H4NC(H)C6H4OCH2CH2SMe)(&eta / 5-C2H5]2 was synthesized and deposited as a selfassembled monolayer (SAM) on a gold electrode. Effective electronic communication between the Ru(II) centers and the gold electrode was established by electrostatically cycling the Shiff base-doped gold electrode in 0.1 M NaOH from -200 mV to +600 mV. The SAMmodified gold electrode (Au/SAM) exhibited quasi-reversible electrochemistry. The integrity of this electro-catalytic SAM, with respect to its ability to block and electro-catalyze certain Faradaic processes, was interrogated using Cyclic and Osteryoung Square Wave voltammetric experiments. The formal potential, E0', varied with pH to give a slope of about - 34 mV pH-1. The surface concentration, &Gamma / , of the ruthenium redox centers was found to be 1.591 x 10-11 mol cm-2. By electrostatically doping the Au/SAM/Horseradish peroxidase at an applied potential of +700 mV vs Ag/AgCl, a biosensor was produced for the amperometric analysis of hydrogen peroxide, cumene hydroperoxide and tert-butylhydroperoxide. The electrocatalytic-type biosensors displayed typical Michaelis-Menten kinetics with their limits of detection of 6.45 &mu / M, 6.92 &mu / M and 7.01 &mu / M for hydrogen peroxide, cumene hydroperoxide and tert-butylhydroperoxide respectively.