Šiame darbe tiriama galio ir bismuto plėvelinių elektrodų formavimo in situ ir ex situ metodais ypatumai skirtingose sistemose. Optimizuotos bismuto ir galio plėvelinių elektrodų panaudojimo sąlygos sunkiųjų metalų koncentracijos nustatymui. Atliekant bismuto plėvelės nusodinimą ant stikliškosios anglies elektrodo nustatyta, kad papildomas Br- pridėjimas į tiriamąjį tirpalą keičia bismuto plėvelės morfologines savybes ir formuojasi tolygesnė bismuto plėvelė sudarydama kristalines struktūras. Reoksidacinė bismuto smailė pasislenka į neigiamesnių potencialo verčių pusę, kas rodo elektrokatalizinį Br- efektą bismuto plėvelės formavimuisi. Nustatyta, kad Cd(II) pridėjimas į tiriamąjį tirpalą lemia lėtesnį bismuto plėvelės nusodinimą, o Pb(II) pridėjimas katalizuoja bismuto plėvelės nusodinimą. Taip pat nustatyta, kad Pb(II) katalizuoja ir kitų metalų jonų nusodinimą. Bismuto plėvelinis elektrodas sėkmingai pritaikytas sunkiųjų metalų Cu(II), Zn(II), Pb(II), Cd(II) koncentracijos nustatymui pramoniniuose vandens mėginiuose. Gautos Zn(II), Cd(II), Cu(II) ir Pb(II) kalibravimo kreivės, kurių korealiacijos koeficientai atitinkamai yra 0,997, 0,997, 0,999 ir 0,998. Optimizuotos galio plėvelės nusodinimo sąlygos ant stikliškosios anglies elektrodo. Geriausi rezultatai gauti atliekant galio plėvelės nusodinimą 0,1 M acetatiniame buferyje (pH = 4,5) 40o C temperatūroje. Optimizuotas nusodinimo laikas ir potencialas atitinkamai yra 120 s ir -1,7 V. Tiriant galio jonų įtaką Pb(II) ir... [toliau žr. visą tekstą] / In this work the gallium and bismuth film plating in situ and ex situ processes were investigated. The metal film plating conditions for determination of heavy metals in water samples were optimized. When depositing Bi films on glassy carbon electrode it was found, that the addition of Br-1 changes the BiFE morphology making it more uniform and forming crystalline aggregates. The reoxidation peak of Bi was shifted to more negative potentials showing the electrocatalytic effect of bromide for the bismuth film. The addition of the other metal ions to the deposition solutions caused changes in the morphology of the Bi film It has been shown, that Cd was slowing the Bi film deposition and Pb was catalyzing this deposition. Zn(II), Cd(II), Cu(II) and Pb(II) ions were determined in the water samples using bismuth film electrode. The linear calibration curve of each metal was obtained. Good linear responses of the peak area vs. concentration were obtained for Zn(II), Cd(II), Pb(II) and Cu (II) with correlation coefficients of 0.997, 0.997, 0.999 and 0.998 respectively. The possibilities of gallium film plating were studied. The glassy carbon substrate was chosen for optimization. The optimized deposition conditions were: supporting electrolyte 0.1 M acetate buffer, deposition potential -1.7 V, deposition time 120 s, deposition temperature 40oC. The gallium influence on Pb(II) and Cd(II) deposition at the glassy carbon electrode was studied. It has been shown that Pb(II) and Cd(II)... [to full text]

Determination of bio-material by using enzyme, fluorophore or metal-nanoparticles as markers is very important. Generally, gold-nanoparticles have been used frequently as marker for increasing the sensitivity in bio-chemical assay. In this research, gold-nanoparticles were used as marker for immunoassay, DNA sequence assay, and protein analysis. However, the size of gold-nanoparticles affects directly the results of electrochemical detection. For improving the sensitivity of electrochemical method, enlargement of gold-nanoparticles was used in this study. By electroless deposition, Au will be deposited on the surface of gold-nanoparticles. The electrochemical response will thus be increased substantially. In immunoassay and DNA sequence assay, traditional 96-wells microtiter plate was used for immobilizing antibody or oligonucleotide, and the gold-nanoparticles were marked subsequently base on the immunoreaction or protein reaction of streptavidin and biotin. After gold-nanoparticles were enlarged, they were dissolved and transferred to an electrochemical cell for square wave stripping voltammetry¡]SWSV¡^analysis. Under optimal experimental condition, dynamic range of 1 ~ 500 pg/mL and 0.52 ~ 1300 aM were found respectively for RIgG and Target DNA analysis, and a good linear relationship¡]R2 = 0.9975 and 0.9982¡^. The relative standard deviation¡]R.S.D.¡^ of blank were 2.8 % and 2.4 %¡]n = 11¡^for immunoassay and DNA assay, respectively. And the variance was 2.4 %¡]n = 9¡^and 2.4 %¡]n = 12¡^for immunoassay and DNA assay, respectively. The detection limit¡]based on S/N = 3¡^of RIgG and DNA were 0.25 pg/mL and 0.52 aM, respectively. They are very competitive compared with similar results reported in the literature. Additional, a gold nanoelectrode ensemble¡]GNEE¡^coupled microchip system was developed for bio-electrochemical analysis. Due to the difference in mobility of urea and urease were mixed and allowed the enzymatic reaction to proceed in microchannel. The enzymatic product NH4+ was determined by the coupled GNEE at the outlet of the channel. Another experiment of streptavidin conjugated gold-nanoparticles¡]streptavidin-Au¡^, reductant and gold-ion¡]Au3+¡^solution was be applied here, too. The product, NH4+ or Au3+ was passed through downstream of microchannel and detected by GNEE of electrochemical system. Satisfactory linear relationship¡]R2 = 0.9778 and 0.9657¡^were found from 0.1 mM to 50 mM for NH4+ and urea in the range of 0.02 mM to 5.0 mM, respectively. The other satisfactory linear relationship¡]R2 = 0.9842 and 0.9507¡^ were found between 3.75 mg/mL and 3.75 g/mL for Au3+ and streptavidin-Au in the range of 0.2 ng/mL to 100 ng/mL, respectively. Variances of 2.5 %¡]n = 6¡^was found for analysis of with the microchip system.

[pt] O cloridrato de sibutramina está entre os sacietógenos mais prescritos para o controle da obesidade e tem sido adicionado, de forma não declarada, a alimentos protéicos para esportistas. Nenhuma metodologia analítica é descrita em compêndios oficiais para a determinação de sibutramina. O presente trabalho objetiva o desenvolvimento e a validação de métodos analíticos baseados na voltametria de pulso diferencial (DPV) e na voltametria de onda quadrada (SWV) para quantificação do cloridrato de sibutramina em fármacos e em alimentos protéicos. A influência dos parâmetros eletroquímicos foi estudada para selecionar as melhores condições de trabalho como: eletrólito suporte (tampão Mcllvaine) pH (4,0), velocidade de varredura (40 mV s(-1) para DPV e 240 mV s(-1) para SWV) e amplitude de pulso (50 mV). Não foi possível pré-concentrar a sibutramina no eletrodo de trabalho (gota de mercúrio). O comportamento eletroquímico desta substância no eletrodo de mercúrio também foi investigado a partir de estudos com voltametria cíclica. A redução da sibutramina é aparentemente reversível envolvendo a participação de 1 próton e 1 elétron. O potencial de pico da sibutramina é cerca de - 100 mV (Ag/AgCl 3 mol L-1). No processo de validação foram avaliadas as faixas de resposta linear (do limite de quantificação até 33,3 mg L(-1) em ambos os métodos), o limite de detecção (0,4 para DPV e 0,3 mg L(-1) para SWV), e o limite de quantificação (1,4 para DPV e 1,1 mg L(-1) para SWV). A precisão do método foi satisfatória. Testes de recuperação indicaram 90,4 % em ambos os métodos. O desempenho das técnicas voltamétricas foi comparado estatisticamente com a técnica CLAE e não houve diferença significativa entre os resultados obtidos. / [en] Sibutramine hydrochloride is among the most prescribed satiety inducer for obesity control and it has also been added, in a fraudulent way, in proteinrich food complement for athletes. There is no analytical method for sibutramine described in the official literature. The goal of this work is to develop and validate electroanalytical methods for the determination of sibutramine in pharmaceuticals and in protein-rich food complements. Differential pulse voltammetry (DPV) and square wave voltammetry (SWV) were the techniques employed. The influence of electrochemical parameters was studied in order to select the best working conditions such as supporting electrolyte (Mcllvaine buffer), pH (4.0), scan rate (40 mV s(-1) for DPV and 240 mV s(-1) for SWV) and pulse amplitude (50 mV). The pre-concentration of sibutramine in the working electrode (mercury drop) was not possible. The electrochemical behavior in the mercury electrode was also investigated using cyclic voltammetry. The reduction of sibutramine is probably reversible and involves of 1 proton and 1 electron. The peak potential of sibutramine is about - 100 mV (Ag/AgCl3 mol L(-1)). In the validation process, the linear range of the analytical response (from the limit of quantification to 33.3 mg L-1, in both methods), the limit of detection (0.6 for DPV and 0.4 mg L(-1) for SWV) and the limit of quantification (1.8 for DPV and 1.1 mg L(-1) for SWV) were evaluated. Satisfactory precision was achieved. Recovery tests produced results of 90.4% for both methods. These results were compared with the ones achieved by HPLC and no significant statistical difference was found between them.

Made available in DSpace on 2016-08-19T12:56:44Z (GMT). No. of bitstreams: 1 Dissertacao Daniel.pdf: 1759359 bytes, checksum: 8e118ed0eeb57413abe7a81e44a65d3f (MD5) Previous issue date: 2013-06-03 / Despite the advantages of bismuth film electrode for the determination of trace metals and organic compounds, the Cu²⁺ is an element that has problems when measured with this electrode, since its potential is very close to the Bi³⁺, causing overlapping of peaks. This work presents an alternative to eliminate the interference of Bismuth in the determination of copper in using bismuth film electrodes (BiFE), prepared ex situ mode. The ethanol fuel samples without pre-treatment and biodiesel samples previously digested were used in order to evaluate this electroanalytical procedure. The optimization of the parameters was performed using a complete factorial design 2³ with center point. After several voltammetric experiments, optimal conditions for the determination of Cu²⁺ were the following: Edep = -1.3 V; tpre = 120s; Frequency: 60 Hertz. The voltammograms using anodic stripping voltammetry method in the square wave mode and their corresponding standard addition curves indicated that the bismuth film electrode provides a sensitive and useful procedure for the determination of Cu²⁺ in biofuels. Experiments carried out by the successive addition of aliquots of a standard solution of Cu²⁺, yielded a linear response of peak current to the concentration of metal ion. Good detection limits have been obtained for the determination of Cu²⁺ in ethanol fuel, soybean oil and tallow biodiesels respectively (4.9 x 10ˉ⁸ mol Lˉ¹; 5.60 x 10ˉ⁸ mol Lˉ¹, 1.79 x 10ˉ⁸ mol Lˉ¹). The accuracy was assessed through recovery test (recoveries of 85.6% to 97.05%) and the precision was expressed by the coefficient of variation that ranged from 10% to 18%. The method was successfully applied to two different samples of biodiesel and ethanol fuel and analyzed in triplicate. / Apesar das vantagens do Eletrodo de Filme de Bismuto (BiFE), na determinação de metais traços e compostos orgânicos, o Cu²⁺ é um elemento que apresenta problemas quando quantificado com este eletrodo, uma vez que seu potencial é muito próximo ao do Bi³⁺, causando a sobreposição de picos. Este trabalho apresenta uma alternativa para eliminação da interferência do bismuto na determinação de Cu²⁺ em biocombustíveis (etanol e biodiesel), usando um BiFE, preparado no modo ex situ. As amostras de etanol combustível foram usadas sem tratamento prévio, enquanto as amostras de biodiesel foram previamente digeridas. A otimização dos parâmetros foi realizada com o uso do planejamento fatorial completo 2³ com ponto central. Após vários experimentos voltamétricos, as condições ideais para a determinação de Cu²⁺ foram: Edep = -1,3 V; tpré = 120 s; Frequência: 60 Hertz. Os voltamogramas e suas correspondentes curvas de adição padrão indicaram que o uso do BiFE com a técnica Voltametria de Redissolução Anódica (ASV), no modo onda quadrada, indicaram que o procedimento é adequado, útil e sensível para a determinação de Cu²⁺ em biocombustíveis. Os experimentos realizados, pela adição sucessiva de alíquotas da solução padrão de Cu²⁺ proporcionaram uma resposta linear entre a corrente de pico e a concentração do íon metálico. Bons limites de detecção foram obtidos para a determinação do Cu²⁺ em Etanol combustível, biodiesel de óleo de soja e de sebo respectivamente (4,90x10ˉ⁸ mol Lˉ¹; 5,60x10ˉ⁸ mol Lˉ¹; 1,79x10ˉ⁸mol Lˉ¹). A exatidão foi avaliada através do teste de recuperação (recuperações de 85,6% a 97,05%). A precisão, expressa pelo coeficiente de variação (CV: entre 10% e 18%) foi considerada boa. O método foi aplicado com sucesso em amostras reais de biodiesel e Etanol combustível.

The contamination of renal failure patients by metals can be associated to the presence of these metals in the medication, since they can be absorbed by the organism. The level of contamination caused by medication, in these cases, depends strongly on the quality of medication used in the treatment. Among the possible contaminants, there are metals such as aluminum, chromium and nickel. Therefore, the development of analytical methodologies for the quality control of medicaments used by anemic patients is of great importance. In the present work, the presence of Al, Cr and Ni as contaminants in erythropoietin formulations (EPO), a renal antianemic, was investigated by developing and optimizing an adsorptive cathodic stripping voltammetric (AdCSV) method. It involves the optimization of a pretreatment step of samples by using UV irradiation for decomposition of matrix organic components. The AdCSV method is based on the adsorptive deposition of the complex formed at the electrode surface and the subsequent reduction of ligand (or metal) during the cathodic potential scan. The results found for Al, Cr and Ni in the studied samples, after performing the pretreatment step, show the applicability of the method for the determination of Al, Cr and Ni as contaminants in this kind of samples. The developed voltammetric methods are advantageous in relation to other existing methods concerning the high sensitivity of measurement if associated to the pretreatment step by UV irradiation associated with the addition of H2O2. / A contaminação de pacientes com insuficiência renal por espécies metálicas pode estar associada à presença destas na medicação empregada, uma vez que estas espécies podem ser absorvidas pelo organismo do paciente. O nível de contaminação através da medicação, nestes casos, dependerá da qualidade da medicação utilizada no tratamento. Dentre os possíveis contaminantes, estão metais como alumínio, cromo e níquel. Desta forma, o desenvolvimento de metodologias analíticas adequadas ao controle de qualidade dos medicamentos administrados ao paciente é de grande importância. No presente trabalho, investigou-se a presença de Al, Cr e Ni como contaminantes em formulações de eritropoetina (EPO), um antianêmico renal, através do desenvolvimento e otimização de um método voltamétrico adsortivo de redissolução catódica (AdCSV) com a otimização de uma etapa de pré-tratamento das amostras empregando radiação UV para a decomposição dos componentes orgânicos da matriz. O método está baseado na deposição adsortiva do complexo formado (metal-ligante) na superfície do eletrodo e na redução do ligante ou do metal durante a varredura catódica dos potenciais. Os valores de Al, Cr e Ni encontrados nas amostras estudadas, após a etapa de pré-tratamento, demonstram a aplicabilidade do método para a determinação de Al, Cr e Ni como contaminantes neste tipo de matriz. O método voltamétrico desenvolvido é vantajoso em relação a outros métodos existentes, devido à alta sensibilidade da medida quando associada a uma etapa de pré-tratamento da amostra com radiação UV combinado com adição de H2O2.

Voltammetric methods for the determination amphenicol antibiotic chloramphenicol (CAP) and quinolone antibiotic Ofloxacin (OFL) were developed. TTechniques differential pulse voltammetry (DPV) and DC voltammetry (DCV) for determination of both substances at boron doped diamond film electrode (BDDFE) were used. The effect of pH of Britton-Robinson buffer was tested and the stability of the signal with repeated measurements was monitored. Optimal pH 6 was used for determining of CAP by both, DPV and DCV techniques. Media of pH 4 for determining of OFL by DPV and DCV was optimal. Under these conditions linear dependences in the calibration concentration region 1.10 -6 - 1.10-4 mol.l -1 were obtained. The limit of determination for the method for CAP by DPV at 3.10 mol.l , by -6 -1 DCV at 3.10 mol.l and for -6 -1 OFL by DPV at 1.10 mol.l -6 -1 and by DCV at 4.10 mol.l -7 -1 was found. The developed methods were used for the determination of CAP in the drug samples Spersadex comp. and OFL determination in drug samples Zanocin 200. Method for solid phase extraction of OFL from samples of urine with voltammetric detection was developed with limit of determination at 7.10 mol.l . -6 -1

Magister Scientiae - MSc (Chemistry) / In this study, graphene oxide was synthesized by oxidizing graphite using the modified Hummer's method. The graphene oxide was characterized by Raman Spectroscopy, Fourier Transform Infrared Spectroscopy, High Resolution Transmission Electron Microscopy, Scanning Electron Microscopy and X-Ray Diffraction for structural and morphological properties. The graphene oxide was electrochemically reduced on a carbon paste electrode followed by the in situ deposition of mercury thin films to achieve electrochemically reduced graphene oxide modified carbon paste metal film electrodes (ERGO-CP-MEs). The experimental parameters (amplitude, deposition time, deposition potential, frequency and rotation speed) were optimized, and the applicability of the modified electrode was investigated towards the simultaneous and individual determination of TI1+ and In3+ at the low concentration levels (?g L-1) in 0.1 M acetate buffer (pH 4.6) using square wave anodic stripping voltammetry (SWASV). The detection limit values for individual analysis at electrochemically reduced graphene oxide modified carbon paste mercury film electrode (ERGO-CP-HgE ) was 2.4 and 1.1 ?g L-1 for TI1+ and In3+, respectively. The detection limit values for simultaneous analysis at ERGO-CPE was 1.32 and 1.33 ?g L-1 and individual analysis was 0.975 and 1.04 ?g L-1 for TI1+ and In3+, respectively.

No description available.

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.