Dissertations / Theses on the topic 'Anodic stripping voltammetry'

This thesis describes the application of macro, micro, ultra-microelectrodes and microelectrode arrays to the measurement of trace concentrations of nickel and cobalt in sediment and natural waters by adsorptive cathodic stripping voltammetric methods. In addition the measurement of tin by adsorptive cathodic stripping voltammetry in sediment and natural waters is discussed. Also, the application of macroelectrodes and microelectrode arrays to the measurement of lead, cadmium and zinc in sediment and natural waters by anodic stripping voltammetry is considered. In all cases the determination of the six metals was optimised by investigating the influence of various significant parameters, such as in-situ mercury plating, complexing agent concentration, scan rate, pulse height, accumulation time and potential, buffer concentration and pH. The results obtained for these investigations are discussed in this thesis
Doctor of Philosophy (PhD)

Thesis (Ph. D) -- University of Western Sydney, Nepean, 1999.
A thesis presented for the degree of Doctor of Philosophy, Centre for Electrochemical Research and Analytical Technology, University of Western Sydney, Nepean. Includes bibliographical references.

This thesis describes a novel application of an artificial neural network and links together the two diverse disciplines of electroanalytical chemistry and information sciences. The artificial neural network is used to process data obtained from a Differential Pulse Anodic Stripping (DPAS) electroanalytical scan and produces as an output, predictions of lead concentration in samples where the concentration is less than 100 parts per billion. A comparative study of several post analysis processing techniques is presented, both traditional and neural. Through this it is demonstrated that by using a neural network, both the accuracy and the precision of the concentration predictions are increased by a factor of approximately two, over those obtained using a traditional, peak height calibration curve method. Statistical justification for these findings is provided Furthermore it is shown that, by post processing with a neural network, good quantitative predictions of heavy metal concentration may be made from instrument responses so poor that, if using tradition methods of calibration, the analytical scan would have had to be repeated. As part of the research the author has designed and built a complete computer controlled analytical instrument which provides output both to a graphical display and to the neural network. This instrument, which is fully described in the text, is operated via a mouse driven user interface written by the author.

>Magister Scientiae - MSc
Platinum Group Metals (PGMs), particularly palladium (Pd), platinum (Pt) and rhodium (Rh) have been identified as pollutants in the environment due to their increased use in catalytic converters and mining in South Africa (as well as worldwide). Joining the continuous efforts to alleviate this dilemma, a new electrochemical sensor based on a nanoparticle film transducer has been developed to assess the level of these metals in the environment. The main goal of this study was to exploit the capabilities of nanostructured material for the development and application of an adsorptive stripping voltammetric method for reliable quantification of PGMs in environmental samples. In the study reported in this thesis, glassy carbon electrode (GCE) and screen-printed carbon electrode (SPCE) surfaces were modified with conducting films of nanostructured reduced graphene oxide-antimony nanoparticles (rGO-SbNPs) for application as electrochemical sensors. The rGO-SbNPs nanocomposite was prepared by Hummer`s synthesis of antimony nanoparticles in reaction medium containing reduced graphene oxide. Sensors were constructed by drop coating of the surfaces of the carbon electrodes with rGO-SbNPs films followed by air-drying. The nanocomposite material was characterised by: scanning and transmission electron miscroscopies; FTIR, UV-Vis and Ramanspectrosocopies; dc voltammetry; and electrochemical impedance spectroscopy. The real surface area of both electrodes were studied and estimated to be 1.66 × 10⁶ mol cm⁻² and 4.09 × 10³ mol cm⁻² for SPCE/rGO-SbNPs and GCE/rGO-SbNPs, respectively. The film thickness was also evaluated and estimated to be 0.36 cm and 1.69 × 10⁻⁶ cm for SPCE/rGO-SbNPs and GCE/rGO-SbNPs, respectively. Referring to these results, the SPCE/rGO-SbNPs sensor had a better sensitivity than the GCE/rGO-SbNPs sensor. The electroanalytical properties of the PGMs were first studied by cyclic voltammetry followed by indepth stripping voltammetric analysis. The development of the stripping voltammetry methodology involved the optimisation of experimental conditions such as selection of adequate supporting electrolyte, choice of pH and /or concentration of supporting electrolytes, deposition potential, deposition time, stirring conditions. The detection of Pd(II), Pt(II) and Rh(III) in environmental samples were performed SPCE/rGO-SbNPs and GCE/rGO-SbNPs at the optimised experimental conditions For the GCE/rGO-SbNPs sensor, the detection limit was found to be 0.45, 0.49 and 0.49 pg L⁻¹ (S/N = 3) for Pd(II), Pt(II) and Rh(III), respectively. For the SPCE/rGO-SbNPs sensor, the detection limit was found to be 0.42, 0.26 and 0.34 pg L⁻¹ (S/N = 3) for Pd(II), Pt(II) and Rh(III), respectively. The proposed adsorptive differential pulse cathodic stripping voltammetric (AdDPCSV) method was found to be sensitive, accurate, precise, fast and robust for the determination of PGMs in soil and dust samples. The simultaneous determination of PGMs was also investigated with promising results obtained. The AdDPCSV sensor performance was compared with that of inductive coupled plasma mass spectroscopy (ICP-MS) for the determination of PGM ions in soil and dust samples. It was found that though the metals could be determined by ICP-MS technique, it was limited from the standpoints of sensitivity, ease of operation and versatility compared to the AdDPCSV sensor. This study has show cased the successful construction and application of novel SPCE/rGO-SbNPs and GCE/rGO-SbNPs AdDPCSV sensors forthe determination of PGMs in environmental samples (specifically roadside dust and soil samples). The study provides a promising analytical tool for monitoring PGMs pollutants that are produced by automobiles and transported in the environment.

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]
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]

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.
2021-12-31

>Magister Scientiae - MSc
Electrochemical platforms were developed based on pencil graphite electrodes (PGEs) modified with electrochemically deposited graphene (EG) sheets and Nafion-graphene (NG) nanocomposites in conjunction with an in situ plated bismuth-film (EG-PG-BiE and NG-PG-BiE). The EG- and NG-PG-BiEs were used as sensing platforms for determining Zn2+, Cd2+ and Pb2+ by square wave anodic stripping voltammetry (SWASV). EG sheets were deposited onto pencil graphite electrodes by cyclic voltammetric reduction from a graphene oxide (GO) solution, while a dip coating method was used to prepare the NG-PG-BiE. The GO and graphene, with flake thicknesses of 1.78 (2 sheets) and 2.10 nm (5 sheets) respectively, was characterized using FT-IR, HR-SEM, HR-TEM, AFM, XRD and Raman spectroscopy. Parameters influencing the electroanalytical response of the EG-PG-BiE and NG-PG-BiE such as, bismuth ion concentration, deposition potential, deposition time and rotation speed were investigated and optimized. The EG-PG-BiE gave well-defined, reproducible peaks with detection limits of 0.19 μg L-1, 0.09 μg L-1 and 0.12 μg L-1 for Zn2+, Cd2+ and Pb2+ respectively, at a deposition time of 120 seconds. The NG-PG-BiE showed similar detection limits of 0.167 μg L-1, 0.098 μg L-1 and 0.125 μg L-1 for Zn2+, Cd2+ and Pb2+ respectively. For real sample analysis, the enhanced voltammetric sensor proved to be suitable for the detection and quantitation of heavy metals below the US EPA prescribed drinking water standards of 5 mg L-1, 5 μg L-1 and 15 μg L-1 for Zn2+, Cd2+ and Pb2+ respectively.

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Neste trabalho foi desenvolvida uma metodologia analítica visando determinar chumbo em querosene e em óleo lubrificante. A voltametria de redissolução anódica com o eletrodo de filme de bismuto (BiFE) foi empregada com a medição do analito nas amostras realizada em meio microemulsionado. O modo de varredura utilizado foi o de onda quadrada (SWV) sendo o desempenho do BiFE comparado com o desempenho observado com o uso do eletrodo de gota pendente de mercúrio (HMDE), este tradicionalmente utilizado nas análises voltamétricas de metais. Na otimização da composição da microemulsão (ME) para o querosene obtevese melhor resultado, em termos de estabilidade e resposta analítica, com 77% de 1-propanol, 13% de fase aquosa (5% ácido nítrico concentrado e 8% água) e 10% de amostra v/v (valores percentuais em volume). No caso da ME para óleo lubrificante a composição otimizada foi 80% de butanol, 10% de fase aquosa (sendo 5% de ácido nítrico concentrado e 5% de água) e 10% amostra dissolvida em xileno. Em ambos os casos, o ácido nítrico serviu como fonte de eletrólitos e para a conversão de espécies químicas metaloorgânicas de chumbo para a forma inorgânica. Após a otimização dos parâmetros instrumentais, os limites de detecção (3sb/a) foram estimados na ordem de nmol L-1 independentemente do eletrodo empregado. Testes de recuperação em material de referência certificado (NIST 1085a) e em amostras fortificadas com Pb (tanto na forma inorgânica quanto na metaloorgânica) indicaram valores recuperados entre 98 e 100%. Os resultados foram confirmados por análises das mesmas amostras por espectrometria de absorção atômica com atomização eletrotérmica. Foi realizado um estudo para avaliar a magnitude das fontes de incerteza de medição voltamétrica de chumbo e o impacto de cada uma das fontes na incerteza combinada. Verificou-se que a contribuição relacionada com a preparação das soluções (padrões e amostras) foi a mais relevante, indicando a necessidade de se traçar novas estratégias de preparação de soluções e de amostragem para a minimização da incerteza combinada. A partir desse estudo, mostrou-se a viabilidade do uso de meio microemulsionado na determinação eletroanalítica de metais em frações de petróleo mais pesadas.
In the presente work, was developed an analytical method aiming the determination of lead in kerosen and in lubricating oil. Anodic redissolution voltammetry with a bismuth-film electrode was employed by measuring the analyte in the sample microemulsions. Square-wave scanning mode (SWV) was employed and the BiFE performance was compared to the one achieved using the static drop mercury electrode (HDME), the later a more traditional electrode for voltammetric analysis for metals. The optimization of the composition of kerosene microemulsion (ME) indicated best results, in terms of stability and analytical response, with 77% of 1-propanol , 13% of aqueous phase (5% concentrated nitric acid and 8% water) and 10% of sample (percent values in volume). For the lubricating oil, the ME composition was 80% of buthanol , 10% of aqueous phase (5% concentrated nitric acid and 5% water) and 10% of sample previously dissolved in xylene. In both cases, the nitric acid played a role as a source of electrolytes and in converting lead metallo-organic species in the inorganic form. After the optimization of experimental parameters, limits of detection were in the nmol L-1 range no matter the type of electrode employed. Recovery tests in certified reference materials (NIST 1085a) and in lead-fortified samples (either with inorganic and metallo-organic form) indicated recovered values between 98 and 100%. These results were confirmed by analyzing the same samples by electrothermal atomic absorption spectrometry. A study was also made to evaluate the measurement uncertainty sources and magnitudes of the voltammetric determination of lead and the impact of each of the sources in the combined uncertainty. As a result, the contribution of the preparation of solutions (samples and standards) was found to be the most relevant source of uncertainty, indicating the need for establishing alternative strategies for such procedures, aiming the minimization of the combined uncertainty. This work has demonstrated the viability of using microemulsions for eletroanalytical determination of metals in petroleum fractions.

Nos dias de hoje um grande número de pesticidas é utilizado em colheitas, agricultura, transporte de sementes, entre outros. Esses pesticidas são moléculas orgânicas que apresentam em sua estrutura grupos funcionais capazes de formar ligações com íons metálicos, que de forma natural ou por intervenção humana, são encontradas no solo. Estas espécies entram em contato no meio ambiente, e assim, interagem formando ligações, dando forma aos chamados compostos de coordenação, ou complexos. A formação destes complexos pode alterar significativamente as propriedades dos pesticidas e dos íons metálicos, podendo acentuar seu caráter tóxico, sua persistência e degradação. Neste trabalho foram escolhidos dois pesticidas que são bons exemplos deste tipo de molécula. O fungicida Thiram, que apresenta em sua estrutura átomos de enxofre, e assim interage com uma gama de íons metálicos; e o herbicida picloram, que é um derivado piridínico, o qual apresenta um átomo de nitrogênio com pares de elétrons livres e capazes de formar ligações, e um grupamento ácido na posição dois do anel também capaz de interagir com íons metálicos. Com o intuito de se entender melhor como ocorre estas interações, realizou-se este trabalho onde observou-se a complexação dos pesticidas thiram e picloram com quatro íons metálicos previamente selecionados, zinco, cobre, cádmio e chumbo. Dessa forma, deu-se início a um estudo de complexação utilizando o método de Voltametria de Redissolução Anódica em modo de Pulso Diferencial, a fim de se avaliar a ocorrência desta complexação. Para isso, contamos com duas ferramentas muito utilizadas para a avaliação da capacidade complexante de amostras, os métodos de linearização de Scatchard e Langmuir. Com a técnica utilizada foram levantadas curvas de titulação de amostras contento os pesticidas, e a partir dos dados obtidos aplicou-se os cálculos de Langmuir e Scatchard para se obter dois parâmetros importantes, a constante de estabilidade condicional do complexo formado, K\', e a concentração de ligante que participa da reação de complexação em solução, [L]T. Os dados obtidos com ambos pesticidas foram satisfatórios, indicando a ocorrência de complexos. Porém, observou-se que essa interação é maior entre o fungicida thiram e os respectivos metais do que com o herbicida picloram. As constantes de estabilidade condicional para o fungicida thiram se encontram com Log de K\' entre 6 e 7, enquanto as mesmas para os complexos formados entre o herbicida picloram e os íons metálicos se encontram entre 5 e 6. Para se confirmar as medidas de voltametria de redissolução anódica, foram realizadas medidas de espectroscopia na região do ultravioleta visível, bem como medidas de voltametria cíclica e de pulso diferencial.
Nowadays, numerous pesticides are used in crops, agriculture, transport of seeds, among others. These pesticides are organic molecules that present functional groups in their structure which are capable of forming connections with metallic ions, which, whether naturally or by human intervention, are found in the soil. These species enter in contact in the environment, and thus, they interact forming connections, giving form to the so called compound of coordination, or complex. The formation of these complexes can alter significantly the properties of both the pesticides and the metallic ions, being able to enhance toxic character, persistence and degradation. In this work, two pesticides were chosen for being good examples of this type of molecule. The fungicide Thiram, which presents atoms of sulfur in its structure, and thus interact with a range of metallic ions; and the herbicide picloram, a derived pyridinic, which presents a nitrogen atom with pairs of free electrons and capable of forming binding, and an acid group in the position two of the ring, also capable of interacting with metallic ions. In order to better understand how these interactions occur, this work focused where the complexation of pesticides thiram and picloram was observed with four metallic ions previously selected, zinc, copper, cadmium and lead. Hence, a study of complexation was started using the method of Differential Pulse Anodic Stripping Voltammetry, in order to evaluate the occurrence of the complexation. For that, we counted on two tools very frequently used for the viii evaluation of the metal-binding capacity of samples, namely, the linearization methods of Scatchard and Langmuir. Titration curves of the samples containing the pesticide were obtained using the technique, and starting from the data, the calculations of Langmuir and Scatchard were applied in order to obtain two important parameters, stability conditional constant of the formed compound, K\', as well as the ligand concentration that participates in the reaction complexation in solution, [L]T. The data obtained with both pesticides were satisfactory, indicating the occurrence of complexes. However, it was observed that the interaction is larger between the fungicide thiram and the respective metals than with the herbicide picloram. The constants of conditional stability for the fungicide thiram are with LogK\' between 6 and 7, while the same ones for the compounds formed between the herbicide picloram and the metallic íons are between 5 and 6. To confirm the measures of anodic stripping voltammetry, spectroscopy measures were carried out in the area of the visible ultraviolet, as well as measures of cyclic voltammetry and of differential pulse.

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]

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.

Access to safe water supply--a major determinant of public health--is less than 50% in Madagascar, and access to piped, treated water remains out of reach financially for many in the urban and peri-urban areas where available. The Self-supply option of the Pitcher Pump has been meeting the need for household water in coastal areas of Madagascar since the early 1960s and has proven a sustainable option for many. These pumps make use of leaded components in the construction, however, which may pose a health risk for heavy metal intoxication and therefore cause the water to be unsafe for drinking and cooking. This study assesses the potential for lead (Pb) leaching from Pitcher Pump systems into water at levels of health concern. The objectives of this study are to assess Pb concentrations in water drawn from Pitcher Pumps, to determine the relationship between various factors and the Pb levels, to make a preliminary assessment of public health implications of Pb contamination, and to offer informed recommendations to reduce the likelihood of consuming contaminated water. A field study was undertaken to measure concentrations of dissolved Pb in water from Pitcher Pumps under recently flushed and first-draw pumping conditions at 18 households in the city of Tamatave, Madagascar. Variables potentially affecting Pb leaching were determined including pump age, depth to the well screen, pump manufacturer, season of sample collection, and basic water quality indicators. Sampling campaigns were conducted three times over the course of eight months. Time-release case studies were also carried out at two households to determine the time scale over which the Pb concentration in stationary water reaches equilibrium with the Pb-containing system components. Pilot studies of iron (Fe)-for-Pb substitution of select pump system components were carried out at the same two households to attribute the major contribution of Pb leaching to one set of parts and to assess one strategy for decreasing dissolved Pb concentrations. Finally, the Internal Exposure Uptake Biokinetic Model for Lead in Children (IEUBK Model) of the US Environmental Protection Agency (EPA) was employed to estimate realistic blood lead levels (BLLs) in children under five years of age, based on Pb concentrations measured in the water. Of the 18 pumps sampled, 15 produced at least one sample exceeding the World Health Organization (WHO) provisional guideline of 10 [um]g/L dissolved Pb in water. Specifically, 67% of all samples showed concentrations above 10 [um]g/L under first-draw pumping conditions. Flushing the pumps prior to use decreased the Pb levels significantly (p < 0.0001), with only 35% of samples exceeding the provisional guideline. Under flushed conditions, the median Pb concentration in pumped water was 9 [um]g/L, down from 13 [um]g/L at one hour of inactivity. No statistically significant correlations were observed between measured Pb concentrations and factors like the season of sample collection, pump age, manufacturer, or water quality indicators like pH or temperature. Under first-draw conditions, the concentration of Pb in water increased with increasing duration of pump inactivity, until equilibrium was reached with the leaded pump components. For two pumps, substitution of Fe valves for Pb greatly decreased Pb concentrations in the water, from 37-100 [um]g/L and 7-24 [um]g/L down to 3-4 [um]g/L and 2-8 [um]g/L, respectively. Model-predicted geometric mean BLLs in children range from about 2-8 [um]g/dL, in some instances exceeding the Centers for Disease Control and Prevention (CDC) guideline for an elevated BLL (5 [um]g/dL), depending on the exposure concentrations. This study finds that water provided by Pitcher Pump systems in Madagascar frequently exceeds the WHO provisional guideline value for safe consumption under first-draw conditions, and may do so even after flushing the pumps. The Pb concentrations measured in the field have the potential to elevate BLLs in children under five to levels implicated in serious health issues. Leaching of Pb into the water is therefore an issue of concern for users of the Pitcher Pump systems in Tamatave, and likely for other areas served by this technology. Flushing the pumps before water collection generally reduces Pb levels in the water. These results suggest that most of the Pb leaches from pure Pb check valve weights at the mouth of the pump, and consequently, a substitution of Fe weights on the valves greatly reduces Pb concentrations and the probability for exceeding the WHO provisional guideline. Relatively simple operational changes on the part of the pump manufacturers and the pump users might, therefore, help to ensure the continued sustainability of Pitcher Pumps in eastern Madagascar.

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.

In this work a new material, the conducting polymer-DNA composite, has been reported for the first time due to its promise in micro extraction, transfer, and release of cations under controlled potential conditions by using electrochemically assisted solid phase micro extraction (SPME). The Polypyrrole/DNA composite can be formed easily by oxidation of pyrrole monomers in the presence of chromosomal DNA by electropolymerization. Environmental significant pollutants such as Cd, Pb, Hg, Co, Zn, Cu, and Bi metal ions can be extracted from the aqueous solution and are able to be transferred to another medium defined as the release solution where the metals were detected by anodic stripping voltammetry. Using Cd2+ as a model, this method has been examined to optimize its operational condition. Extraction efficiency and potential interference for this method were studied.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Esta dissertação apresenta o desenvolvimento de métodos voltamétricos para a determinação de zinco em amostras comerciais de polivitamínicos, talco e materiais artísticos para pintura (giz pastel) combinando uma extração alcalina com solução aquosa de NaOH 1,0 mol L-1 e eletrodos quimicamente modificados com bismuto. Foram utilizados dois eletrodos para a quantificação de zinco nas amostras, eletrodo de filme de bismuto (BiFE) crescidos in situ sobre carbono vítreo e eletrodo de pasta de carbono quimicamente modificado com a resina de troca iônica fortemente ácida Amberlite® IR 120 e nanoestruturas de bismuto (EPCAmbBi). Verificou-se que a melhor concentração de Bi3+ para o crescimento do filme de Bi sobre carbono vítreo foi 4,0 μmol L-1 utilizando uma solução aquosa de tampão acetato 0,1 mol L-1 (pH = 4,5) como eletrólito de suporte. A melhor condição para a formação das nanoestruturas de Bi no EPC modificado com 10% de Amberlite® IR 120 foi a utilização de 30 s de pré-concentração (circuito aberto) em uma solução aquosa de Bi3+ 0,5 mmol L-1 (pH = 5,5) preparada com a solução do eletrólito de suporte. A curva analítica obtida para o Zn2+ utilizando o BiFE apresentou uma região linear de 0,5 a 5,0 μmol L-1 o valor de Limite de Detecção (LD) foi de 41 nmol L-1. Para o EPCAmbBi foi observado um único intervalo linear na curva analítica construída variando a concentração do Zn2+ de 0,05 a 8,2 μmol L-1, o LD obtido nesta curva foi igual a 10 nmol L-1. O EPCAmbBi apresentou picos de redissolução anódica para Zn2+ mais intensos e estreitos e, portanto, com melhor perfil voltamétrico, com uma sensibilidade superior à obtida com o BiFE. Além disso, o EPCAmbBi apresentou um LD menor do que o obtido com o BiFE. A extração alcalina foi um procedimento de pré-tratamento de amostra eficiente para extrair o Zn2+ da matriz de amostras sólidas, além disso, este método de extração é menos susceptível à interferências do Cu2+, uma vez que este permanece insolúvel como Cu(OH)2 durante a extração. A combinação da extração alcalina com o EPCAmbBi mostrou-se uma forma simples, rápida, eficiente e de baixo custo para a determinação de zinco em amostras de formulações farmacêuticas e de materiais artísticos para pintura (giz pastel), podendo ser empregada como um método alternativo e de menor custo em relação à espectroscopia de absorção atômica.
This dissertation presents the development of voltammetric methods to zinc determination in multivitamin commercial samples, talc, and art materials for painting (soft pastel) combining an alkaline extraction with 1.0 mol L-1 NaOH aqueous solution and bismuth modified electrodes. Two electrodes were used to zinc quantification in the samples, bismuth film electrode (BiFE) plated in situ onto glassy carbon and carbon paste electrode chemically modified with strongly acidic ion exchange resin Amberlite® IR 120 and bismuth nanostructures (EPCAmbBi). It was verified that the best concentration of Bi3+ for Bi film deposition onto glassy carbon was 4.0 μmol L-1 using an 0.1 mol L-1 acetate buffer aqueous solution (pH = 4.5) as supporting electrolyte. The best condition to formation of Bi nanostructures in the EPC modified with 10 % Amberlite® IR 120 was the use of 30 s to pre-concentration (open circuit) in 0.5 mmol L-1 Bi3+ aqueous solution (pH 5.5) prepared with supporting electrolyte solution. The obtained analytical curve for Zn2+ using BiFE presented linear range from 0.5 to 5.0 μmol L-1, the limit of detection (LD) was 41 nmol L-1. For EPCAmbBi only one linear range was observed for the analytical curve varying the Zn2+ concentration from 0.05 to 8.2 μmol L-1, LD obtained in this curve it was equal to 10 nmol L-1. The EPCAmbBi presented the most intense and sharp anodic stripping peaks for Zn2+ presenting, therefore, a better voltammetric profile, with sensitivity higher than obtained with the BiFE. Moreover, the EPCAmbBi presented a LD lower than that obtained with the BiFE. Alkaline extraction was an efficient sample pretreatment to extract Zn2+ from solid samples, besides that, this procedure was less susceptible to interferences from Cu2+, since it remains at extracting vessel as insoluble Cu(OH)2. The combination of alkaline extraction with the EPCAmbBi is a simple, fast, efficient and low cost for the zinc determination in pharmaceutical formulations and art materials for painting (soft pastel) samples, which can be employed as a low-cost alternative method to the atomic absorption spectroscopy.
Dissertação (Mestrado)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
This paper describes the development of a method for quantification Cd2+, Pb2+ and Cu2+ cations, in teas, performed simultaneously, using Square Wave Anodic Stripping Voltammetry carbon nanotube paste electrode modified with bismuth film. Tea is one of the most beneficial and consumed beverage through the world, being prepared from the infusion parts of the plant Camellia sinensis. Most commonly this kind of tea presents metal ions, such as Cd 2+, Pb 2+ and Cu 2+, which offers health risk, in case of being ingested above the limit. To detect these metals, it is necessary to make use of techniques with high sensitivity. The spectrometric methods are the most widely used, but they have a high cost, are laborious and expensive. The voltammetric techniques are characterized by being inexpensive and having equal sensitivity, and even greater than some spectrometric methods. The parameters of the technique used were obtained after optimization with fractional factorial design. The tea samples were prepared through digestion with heating by microwave radiation in a closed system using diluted nitric acid and hydrogen peroxide. The method was validated based on the sample certified plant tissue (forage Marandu) and applied in green and black tea samples. Recoveries of cations Cd 2+, Pb 2+ and Cu 2+ ranged from 79.3 to 107.6%, the certified sample, and 73.3 to 122.1% in the evaluated samples of teas. The detection limits obtained in the simultaneous analysis of Cd 2+, Pb 2+ and Cu 2+ were 0.16; 0.20; 0.39 ug L-1, respectively. Cu2 + was detected only in samples of tea, but the method was efficient for the simultaneous quantification of all metals in the matrix assessed after the addition and recovery.
Este trabalho descreve o desenvolvimento de um método de quantificação dos cátions Cd2+, Pb2+ e Cu2+, em chás, realizada de forma simultânea, empregando voltametria de onda quadrada por redissolução anódica com eletrodo de pasta de nanotubo de carbono modificado por filme de bismuto. O chá é uma das bebidas mais benéficas e consumidas no mundo, sendo preparado a partir da infusão de partes da planta Camellia sinensis. Normalmente são encontrados cátions metálicos, como o Cd2+, Pb2+ e Cu2+, que se ingeridos acima do limite máximo representam riscos à saúde. Para detectar esses metais é necessário fazer uso de técnicas com alta sensibilidade. Os métodos espectrométricos são os que mais amplamente tem sido utilizado, porém apresentam custo elevado, são laboriosos e dispendiosos. As técnicas voltamétrica caracterizam-se por serem baratas e possuir sensibilidade igual e até maior que alguns métodos espectrométricos. Os parâmetros da técnica utilizada foram obtidos após otimização com planejamento fatorial fracionário. As amostras de chá foram preparadas via digestão com aquecimento por radiação micro-ondas em sistema fechado empregando ácido nítrico e peróxido de hidrogênio diluídos. A validação do método foi realizada com base na amostra certificada de tecido vegetal (forrageira Marandu) e aplicada em amostras de chá verde e preto. As recuperações dos cátions Cd2+, Pb2+ e Cu2+ variaram de 79,3 a 107,6%, na amostra certificada, e de 73,3 a 122,1% nas amostras de chás avaliadas. Os limites de detecção obtidos na análise simultânea de Cd2+, Pb2+ e Cu2+, foram 0,16; 0,20; 0,39 μg L-1, respectivamente. Foi detectado apenas Cu2+ nas amostras de chá, porém o método se mostrou eficiente para quantificação simultânea de todos os metais na matriz avaliada após a adição e recuperação.

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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Dependendo da sua origem, o mel pode ter uma mistura de diferentes componentes, principalmente carboidratos, que conferem sabor adocicado ao produto. A concentração mineral é baixa, e depende do ambiente onde o mel é produzido, sendo afetada pela composição do solo, pela geologia e pelas condições geográficas locais. Por ser resultado de um processo de bioacumulação, o mel pode ser utilizado para obter informações a respeito do ambiente em que as abelhas produtoras vivem. O presente trabalho desenvolveu uma metodologia para extração e quantificação de Cu, Pb, Cd e Zn em mel com eletrodo de diamante dopado com boro, por voltametria de pulso diferencial. A metodologia foi otimizada por meio de planejamento de experimentos, com obtenção de modelos de previsão, após um estudo detalhado a cerca da ativação da superfície do eletrodo. O uso de ferramentas estatísticas, como Análise de Componentes Principais, Análise de Variância e superfícies de resposta auxiliaram na obtenção de condições ótimas de análise para os metais com o eletrodo proposto. Para análise de Cu, Pb e Cd utilizou-se o potencial de deposição de -0,95 V vs Ag|AgCl por 240 segundos, em ácido clorídrico 0,1 molL-1. A análise de Zn foi realizada em tampão acetato 0,5 molL-1 com um potencial de deposição de -1,5 V vs Ag|AgCl por 240 segundos. Por se tratar de uma matriz heterogênea e rica em matéria orgânica, um tratamento de digestão da amostra foi necessário. A mineralização do mel em chapa de aquecimento foi o procedimento mais adequado para tratamento da amostra. O método otimizado apresentou seletividade, boa sensibilidade, precisão, exatidão e robustez. A concentração dos analitos encontrados variaram entre 0,242 e 1,378 mgL-1 para o Cu; 0,129 e 0,918 mgL-1 para o Pb e 0,819 e 2,492 mgL-1 para o Zn. O Cd não foi detectado em nenhuma das amostras. As medidas obtidas foram comparadas com eletrodo de carbono vítreo modificado com filme de mercúrio e espectrometria de absorção atômica com forno de grafite, e os resultados encontrados não diferiram estatisticamente, sendo analisados por Análise de Variância.
Depending on the origin, honey can be a mixture of different components, mainly carbohydrates, which give a sweet taste to the product. The mineral concentration is low and depends on the environment where the honey is produced, being affected by soil composition, geology and by the respective geographical locations. Being the result of a process of bioaccumulation, honey can be used to collect information about of environment in which bees live. This study developed a methodology for the extraction and quantification of Cu, Pb, Cd and Zn in honey with boron-doped diamond electrode, by differential pulse voltammetry. The methodology was optimized through design of experiments, obtaining prediction models, after a detailed study concerning the activation of the electrode surface. The use of statistical tools such as Principal Components Analysis, Analysis of variance and response surfaces assisted in obtaining optimum conditions for the analysis of metals with such electrode. For analysis of Cu, Pb and Cd was used the deposition potential of -0.95 V vs Ag|AgCl for 240 seconds, hydrochloric acid 0.1 molL-1. Zn analysis was performed in acetate buffer 0.5 mol L-1 with a deposition potential of -1.5 V vs Ag|AgCl for 240 seconds. Because it is a heterogeneous matrix, rich in organic matter, treatment of digestion of the sample was necessary. The mineralization of honey on heating plate was the most appropriate for treatment of the sample. The optimized method showed selectivity, good sensitivity, precision, accuracy and robustness. The concentration of analytes ranged between 0.242 and 1.378 mgL-1 for Cu, 0.129 and 0.918 mgL-1 for Pb and 0.819 and 2.492 mgL-1 for Zn. The Cd was not detected in any sample. The measurements obtained were compared with glassy carbon electrode modified with mercury film and atomic absorption spectrometry with graphite furnace, and the results did not differ statistically, by Analysis of variance.

Os setores sul e norte do complexo estuarino lagunar de Cananéia-Iguape, sujeitos a diferentes pressões antrópicas, foram estudados quanto às características hidrológicas e hidroquímicas das águas de superfície e fundo, com ênfase às concentrações de zinco, cádmio e chumbo dissolvidos. A amostragem contou com coletas espaciais e temporais, em dois períodos sazonais (outono e primavera) de 2007. Os metais estudados foram: o zinco, devido ação tóxica ou como micronutriente, dependendo de sua concentração, o cádmio e o chumbo, considerados sem função biológica positiva conhecida e com alto grau de toxicidade para a biota. A metodologia utilizada na determinação da concentração dos metais traço foi a voltametria por redissolução anódica. No setor sul, a variação da salinidade foi característica de um sistema estuarino não impactado. Os teores dos metais traço encontrados sofreram variação entre 0,040 e 0,509 ?g L-1 para o zinco, 0,001 e 0,024 ?g L-1 para o cádmio e entre 0, 030 e 0,175 ?g L-1 para o chumbo. No setor norte, a variação salinidade mostrou forte influência de água doce. O zinco sofreu variação entre 0,097 e 0,257 ?g L-1, o cádmio entre 0,004 e 0,024 ?g L-1 e o chumbo 0,033 e 0,259 ?g L-1. Nos dois setores, as concentrações dos metais traço estiveram sempre abaixo dos limites propostos pela legislação ambiental brasileira (CONAMA) e norte-americana (EPAUSA). O presente estudo mostrou um maior do impacto antrópico na região norte, com potencial de exportação para o setor sul e plataforma. As maiores concentrações dos metais traço estudados ocorreram nas águas de fundo, mais próximas à interface com o sedimento. O setor sul, sujeito a uma variação da salinidade mais definida, mostrou maior potencial para a remobilização dos metais traço para a coluna de água com o movimento de maré. O estudo dos ciclos biogeoquímicos dos metais traço deve ser incentivado no monitoramento ambiental da região.
The south and north regions of Cananeia-Iguape estuarine-lagoon system submitted to different anthropic pressures were studied to evaluate their hydrological and hydrochemical characteristics mainly considering the concentrations of dissolved zinc, cadmium and lead. The sampling included spatial and temporal samples obtained in two seasons (autumn and spring) of 2007. The metals studied were zinc as a toxic agent and micronutrient depending on the concentration and cadmium and lead with no biological positive relevance and high toxicity to the biota. The methodology used in the trace metals determination was anodic stripping voltammetry. In the south portion the salinity variation was characteristic of non-impacted estuaries. The zinc concentrations ranged from 0,040 to 0,509 ?g L-1. The cadmium ranged from 0,001 to 0,024 ?g L-1. The lead content ranged from 0,030 to 0,175 ?g L-1. In the north portion, the salinity variation showed high influence of fresh water. The zinc concentrations ranged from 0,097 to 0,257 ?g L-1. The cadmium concentrations ranged from 0,004 to 0,024 ?g L-1. The lead values ranged from 0,033 to 0,259 ?g L-1. The concentration of trace metals on both portions were below the limits proposed by the Brazilian environmental law (CONAMA) and North American (EPAUSA) legislation. The present study revealed higher anthropic impact in the north region with exporting potential to the south and to the continental shelf. Higher trace metals concentrations were observed in the bottom waters near to the sediment interface. The south region, submitted to most defined tide movements, showed an important potential for trace metals remobilization to the water column. The trace metals biogeochemistry cycles study should be enhanced for better environmental monitoring.

Esta dissertação descreve o desenvolvimento de uma metodologia de determinação de Cu(II), Pb(II), Cd(II) e Zn(II) em amostras ambientais por voltametria de redissolução anódica (ASV) automatizada com sistema de Análise por Injeção Sequencial (SIA). Sensores impressos com o eletrodo de trabalho de filme fino de mercúrio foram utilizados em uma cela de fluxo. As determinações foram feitas por adição de padrão, com o sistema SIA fazendo a diluição em linha da solução padrão de referência e formando na bobina coletora e auxiliar um segmento contendo as zonas de amostra, solução padrão e solução de diluição. A concentração do padrão preparada nesse segmento gerou um sinal de corrente indistinguível do sinal gerado por uma solução padrão de mesma concentração preparada em batelada em balão volumétrico. Os limites de quantificação e detecção foram da ordem de µg L-1, comparáveis à de técnicas de espectrometria atômica com detecção óptica, cujos custos instrumentais e de manutenção são significativamente maiores. Com o sistema proposto os limites de quantificação e detecção podem ser aumentados ou diminuídos pela simples alteração dos parâmetros como vazão e número de reversões de fluxo, bem como o tempo de deposição no potenciostato. Os limites de detecção e quantificação foram, respectivamente, de 1,3 e 4,3 µg L-1 para o Cu(II), 1,4 e 4,6 µg L-1 para o Pb(II), 0,6 e 1,8 µg L-1 para o Cd(II) e 4,2 e 14 µg L-1 para o Zn(II). Esses limites de detecção e quantificação foram obtidos quando o método funcionou com volume de amostra de 1000 µL, vazão de 10 µL s-1 (durante a etapa de deposição), e utilizando 3 reversões de fluxo (volume de reversão = 950 µL), totalizando um tempo de deposição de 315 segundos. O potenciostato, trabalhando sincronicamente com o sistema SIA operou com potencial de condicionamento de -0,1 V vs. pseudo referência de Ag (100 s), potencial de deposição de -1,0 V para Cu(II), Pb(II) e Cd(II) e de -1,3 V para Zn(II) (315 s), frequência de onda quadrada de 100 Hz, incremento de potencial de 6 mV e altura de pulso de 40 mV. Para determinação de Zn(II) foi necessário depositar Ga0 no eletrodo de trabalho e evitar a formação do intermetálico de Zn0 com Cu0. Estudos de interferentes não apontaram desvios significativos em interferentes aniônicos e catiônicos, mas apresentaram desvios significativos na presença de ácidos húmicos e ácidos fúlvicos. A exatidão do método foi avaliada por estudos de adição e recuperação em amostra de água que resultaram taxas de recuperação próximas de 100%. A exatidão também foi avaliada pelas porcentagens de recuperação das concentrações dos metais da amostra certificada de sedimento CRM-701 submetido ao processo de extração sequencial BCR®. As concentrações obtidas foram testadas pelo teste t de Student, mostrando que os desvios dos valores obtidos em relação aos valores certificados não sugerem a existência de diferenças estatísitcamente significativas.
This dissertation describes the development of a methodology for determination of Cu(II), Pb(II), Cd(II) and Zn(II) in environmental samples by anodic stripping voltammetry (ASV) automated by Sequential Injection Analysis (SIA). Screen printed thin mercury film sensors were used as working electrode in a flow cell. The determinations were made by standard addition, with the SIA system performing the inline dilution of the reference standard solution and forming a segment inside the holding coil containing zones of sample, standard and dilution solutions. The concentration of the standard prepared in this segment generated a current signal undistinguishable from the signal generated by a standard solution of the same concentration prepared manually in a volumetric flask. The limits of quantification and detection were at the level of µg L-1, comparable to those of atomic spectrometry techniques with optic detection, whose instrumental and maintenance costs are significantly higher. With the proposed system the limits of quantification and detection can be increased or lowered by simple change of parameters such as flow rate and number of flow reversals, as well as the deposition time at the potenciostat. The limits of detection and quantification were, respectively, 1.3 and 4.3 µg L-1 for Cu(II), 1.4 and 4.6 µg L-1 for Pb(II), 0.6 and 1.8 µg L-1 for Cd(II) and 4.2 and 14 µg L-1 for Zn(II). These limits of detection and quantification were obtained for a sample volume of 1000 µL, flow rate of 10 µL s-1 (during the deposition step), and utilizing 3 flow reversals (volume of reversion = 950 µL) totalizing a deposition time of 315 seconds. The potentiostat worked synchronically with the SIA system performing a conditioning potential of -0,1 V vs pseudo reference of Ag (100 s), deposition potential of -1,0 V for Cu(II), Pb(II) and Cd(II) or -1,3 V for Zn(II) (315 s), square wave frequency of 100 Hz, potential step of 6 mV and pulse height of 40 mV. For determination of Zn(II), deposition of Ga0 on the working electrode was necessary to avoid the formation of intermetallic between Zn0 and Cu0. Studies of interference did not point significant deviation for anionic and ionic potentially interfering substances, but exhibited significant deviations in the presence of humic and fulvic acids. The accuracy of the method was assessed by spike and recovery experiments in a water sample that resulted recovery rates near of 100%. The accuracy was also assessed by percentages of recovery of concentrations of metals in the certified sediment sample CRM-701 undergoing the sequential extraction procedure of BCR®. The concentrations obtained were tested by test t of Student, showing that the deviations of the obtained values don´t suggest the occurrence of statistically significant differences

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Metal traces are often detected in biodiesel samples due to its presence in the raw materials or solubilization during its manufacturing. Thus, this work aims to propose an electroanalytical methodology for the direct determination of Ca²⁺ in biodiesel using with a glassy carbon electrode. The metal quantification was developed according to Anodic Stripping Voltammetry Mode square-wave (SWASV) technique applying EDTA as the complexing agent. Thus, all samples were pretreated according to wet acid digestion processing and microwave radiation. Therefore, a solution of 4 mL of ultrapure nitric acid (HNO₃), 2 mL of hydrogen peroxide (H₂O₂) and 1 mL deionized water were added to 300 mg sample of biodiesel. Later, such mixtures was thermal treated at 90 °C using 300 W (10 min) and 450 W (5 min) of microwave radiations. The analytical determinations were carried out using ammonium buffer (0.01 mol Lˉ¹, pH = 9.4) as supporting electrolyte and EDTA (1x10ˉ² mol Lˉ¹) as ligand. The optimized voltammetric conditions were EDEP = -1000 mV; tpre = 120 s; Frequency = 30 Hz; Amplitude = 100 mV and ΔEstep = 15 mV. The accuracy was verified by recovery tests. In all cases, the metal quantizations were statistically consistent considering the t-test student for a confidence level of 95%. The CV values were lower than 11%, the recoveries were between 102.9% to 102.4% and the values of the detection limits were 1.9 x 10ˉ⁸ and 1.6 x 10ˉ9 mol Lˉ¹ for the samples, showing good accuracy and sensitivity of the proposed method. The values obtained for the samples ranged from 2.8 x 10ˉ⁸ ± 5.0 x 10ˉ⁸ mol Lˉ¹ and 3.4 x 10ˉ7 ± 5.0 x 10ˉ9 mol Lˉ¹ for Ca²⁺ in evaluated biodiesel.
A presença de metais no biodiesel está diretamente relacionada com a matéria-prima utilizada e também com o processo utilizado para a obtenção do biodiesel. Este trabalho apresenta um procedimento eletroanalítico simples para a determinação direta de Ca2+ em biodiesel com um eletrodo de carbono vítreo. A determinação foi feita com a técnica Voltametria de Redissolução Anódica no modo onda quadrada (SWASV), usando-se o EDTA como agente complexante. As amostras de biodiesel foram submetidas a um processo de digestão ácida por via úmida por radiação, em sistema fechado, com o uso de um microondas. O procedimento para digestão das amostras foi realizado pela adição de 4 mL de ácido nítrico ultrapuro (HNO₃), 2 mL de peróxido de hidrogênio (H₂O₂) e 1 mL de água deionizada em 300 mg de amostra de biodiesel. As amostras foram aquecidas a uma temperatura de 90 oC, durante 10 minutos, em potência de 300 W e 5 minutos em potência de 450 W. As determinações foram feitas utilizando-se tampão amônio (0,01 mol Lˉ¹), pH 9,4, como eletrólito suporte e EDTA 1 x 10ˉ² mol Lˉ¹ como ligante, nas seguintes condições: potencial de deposição (Edep) = -1000 mV; tempo de pré-concentração (tpré) = 120 s; frequência (Freq.) = 30 Hz; amplitude (Amp) =100 mV e potencial de escada (ΔEescada) =15 mV. A exatidão do método foi verificada através de testes de recuperação. Os resultados foram concordantes, estatisticamente, considerando o teste-t de student para um nível de confiança de 95%. Os valores de CV foram menores que 11%, as recuperações foram entre 102,9 % e 102,4 % e os valores dos limites de detecção foram de 1,9 x 10ˉ⁸ e de 1,6 x 10ˉ9 mol Lˉ¹ para as amostras analisadas, mostrando boa exatidão e sensibilidade do método proposto. Os valores obtidos para as amostras analisadas situaram-se entre 2,8 x 10ˉ6 ± 5,0 x 10ˉ⁸ mol Lˉ¹ e 3,4 x 10ˉ7 ± 5,0 x 10ˉ9 mol Lˉ¹ para Ca²⁺ nas amostras de biodiesel.

O tributilestanho é uma espécie química que tem demonstrado ser altamente tóxica para organismos vivos. É utilizado em tintas anti-incrustantes, aplicadas sobretudo no revestimento de cascos de embarcações e outras estruturas marinhas com o objectivo de evitar a deposição de organismos vivos. O tributilestanho, tal como os seus derivados, apresenta um comportamento muito complexo, nomeadamente no que respeita à determinação e quantificação através de métodos electroquímicos. Este trabalho apresenta uma nova abordagem, aliando a voltametria de onda quadrada de redissolução anódica a redes neuronais artificiais. Esta técnica, oriunda da Área Científica da Inteligência Artificial, permite analisar os dados obtidos por voltametria de onda quadrada de redissolução anódica e encontrar um padrão comportamental que permite quantificar o tributilestanho em amostras de água salgada recolhidas no porto de Sesimbra. É uma técnica muito rápida de executar, de baixo custo e que apresenta taxas de recuperação consideravelmente elevadas; ABSTRACT:Tributyltin is a chemical species that has proven to be highly toxic to living organisms. It is used in antifouling paints, especially in boat hulls coating and other marine structures in order to prevent the deposition of living organisms. TBT and its derivatives have a very complex behavior, particularly when it comes to the determination and quantification using electrochemical methods. This project presents a new approach, combining the square wave anodic stripping voltammetry with artificial neural networks. This technique, emanating from the Scientific Area of Artificial Intelligence, enables the analysis of the data obtained by square wave anodic stripping voltammetry and helps in finding a pattern that allows the quantification of Tributyltin in the seawater samples collected at the Sesimbra harbor. This is a very fast and low cost technique which presents considerably high recovery rates.

El incremento del vertido de sustancias contaminantes al medio ambiente, debido al desarrollo industrial y los malos hábitos de consumo, han provocado la ruptura del equilibrio de muchos ecosistemas llegando afectar, en muchas ocasiones, a los humanos. Con el objetivo de controlar y disminuir estos efectos, los gobiernos han dirigido acciones para legislar y regular el vertido de sustancias tóxicas al medio. De esta manera el Gobierno Nacional de España ha financiado a nuestro grupo de investigación, el proyecto del Plan Nacional en Ciencia y Tecnología Química titulado “Desarrollo de métodos automáticos de análisis. Aplicación a planes de vigilancia ambiental”, con referencia CTQ 2010-15541. La presente tesis forma parte de este proyecto siendo su objetivo general el desarrollo de nuevos métodos automáticos para la determinación de especies químicas de interés ambiental. En la introducción de la tesis se realiza una revisión sobre la automatización del laboratorio químico mediante técnicas de análisis en flujo y se describen las dos utilizadas en esta tesis. Seguidamente se revisa la aplicación de estas técnicas a la automatización de los métodos electroquímicos, especialmente la conductimetría y la voltamperometría redisolución anódica. En el tercer apartado de la introducción se recogen los aportes de las técnicas de flujo en la automatización de procesos de tratamientos de muestras como la difusión gaseosa y la extracción líquido-líquido. De esta última técnica se resume su evolución histórica hasta los métodos más recientes descritos que logran la automatización total del proceso de extracción y que se pudieran clasificar dentro de la tercera generación de las técnicas en flujo. En el último apartado de la introducción se trata la automatización de métodos cinético-catalíticos mediante técnicas de análisis en flujo, destacando el elevado potencial que tienen estos métodos para el análisis de trazas y el bajo número de trabajos publicados donde se consigue la automatización de los mismos. Contenido de la investigación En esta tesis se han utilizado dos técnicas de análisis en flujo, el análisis por inyección en flujo multijeringa (MSFIA) y los sistemas en flujo multibombas (MPFS), acopladas a dos métodos de tratamiento de muestras, la difusión gaseosa y la extracción líquido-líquido, y tres técnicas de detección, la voltamperometría de redisolución anódica, la conductimetría y la espectrofotometría, para obtener cinco sistemas automáticos de análisis. Los sistemas desarrollados han sido aplicados a la determinación, fundamentalmente en agua de mar, de cinco analitos inorgánicos: cadmio, cromato, yoduro, amonio y carbono inorgánico total, en muestras ambientales. Durante el desarrollo de estos sistemas y el estudio de las técnicas utilizadas, se han solucionado problemas relacionados con la automatización de las técnicas en flujo, lo que ha mejorado significativamente las características analíticas de los métodos presentados en comparación con otros similares reportados en la literatura. Entre estas mejoras se encuentran por ejemplo el incremento de la reproducibilidad y sensibilidad de las determinaciones, la disminución de los volúmenes de reactivos y muestras utilizados, la reducción de las dimensiones del sistema y de los costes de la instrumentación, así como el aumento del grado de automatización del proceso analítico: tratamiento de la muestra, calibración y detección. Los trabajos presentados en esta tesis son los siguientes: 1- Un método simple, económico, portátil y automatizado mediante MSFIA que permite la determinación de cadmio mediante voltamperometria de redisolución anódica usando electrodos impresos con película de bismuto. (SPE- BiF-ASV- SFIA) 2- Un sistema automatizado mediante la técnica de MSFIA para la determinación de amonio en muestras de aguas naturales y marinas utilizando la difusión gaseosa y la detección conductimétrica. (C-GD-MSFIA) 3- Un analizador automático, basado en la técnica de MPFS, para la determinación de amonio y de carbono inorgánico total en muestras de aguas marinas usando difusión gaseosa y detección conductimétrica. (C-GD-MPFS) 4- Un sistema totalmente automatizado de microextraccion líquido-líquido dentro de la jeringa de una bureta automática para la determinación espectrofotométrica de cromo (VI) en muestras de aguas naturales. (In syringe-MSA-DLLME) 5- Un chip conductor de microfluidos para la automatización mediante MSFIA de un método cinético-catalíticos que permita el análisis de ioduro en agua de mar y fármacos con un consumo muy reducido de reactivos. (CHIP-MSFIA-Catalytic) Conclusiones Se han desarrollado nuevos sistemas automáticos para la determinación de analitos inorgánicos de interés ambiental. La utilización de técnicas de análisis en flujo multiconmutadas, como MSFIA y MPFS, han demostrado ser muy útiles en la automatización de sistemas de análisis que utilizan diferentes técnicas de detección (electroquímicas y espectrofotométricas), de pretratamiento de muestra y de métodos de determinación cinéticocatalíticos. Los sistemas desarrollados han demostrado su efectividad en la determinación de analitos inorgánicos (cadmio, cromato, yoduro, amonio y carbono inorgánico total) en muestras tan complejas como las aguas de mar, aguas residuales o preparados farmacéuticos. Bibliografía 1.Henríquez C, Laglera LM, Alpizar MJ, Calvo J, Arduini F, Cerdà V: Cadmium determination in natural water samples with an automatic multisyringe flow injection system coupled to a flow-through screen printed electrode. Talanta 2012, 96(0):140-146. 2.Henríquez C, Horstkotte B, Cerdá V: Conductimetric determination of ammonium by a multisyringe flow injection system applying gas diffusion Int J Environ Anal Chem 2012:1-17. 3.Henríquez C, Horstkotte B, Cerdá V: A highly reproducible and robust solenoid micropump system for the analysis of total inorganic carbon and ammonium using gas diffusion with conductometric detection. Talanta 2013, In review 4.Henríquez C, Horstkotte B, Solich P, Cerdá V: In-syringe magnetic stirring assisted liquid-liquid microextraction for spectrophotometric determination of Cr (VI) in waters. Analytical and Bioanalytical Chemistry 2013, Accepted/in press. 5.Abouhiat FZ, Henríquez C, Horstkotte B, El Yousfi F, Cerdà V: A miniaturized analyzer for the catalytic determination of iodide in seawater and pharmaceutical samples. Talanta 2013, 108(0):92-102.
Introducción The increasing discharge of pollutants into the environment due to the industrial development and consumer habits have caused the increasing unbalance of many ecosystems, already affecting in many occasions human species itself. In order to control and reduce these effects, many governments have initiated actions to control the discharge of toxic substances into the environment. In this way, the Spanish Government has funded, to our research group, the project of the National Science and Technology Chemistry entitled “Development of automated methods of analysis. Application to environmental monitoring plans”, with reference CTQ 2010- 15541. This PhD thesis is part of this overall project with the main objective of the development of new automated methods for the determination of some chemical species of environmental interest. In the first part of the introduction of this thesis, the automation of different procedures in a chemical laboratory by the use of flow techniques is reviewed and the two selected flow techniques are described. In the second section, the application of these techniques in the automation of electrochemical methods, especially conductometry and anodic stripping voltammetry, is reviewed. In the third section of the introduction, the contributions of flow techniques to the automation sample pretreatment are discussed, especially for gaseous diffusion and liquid-liquid extraction. Moreover, it was reviewed the historical evolution and the most recent reported methods to achieve the full automation of liquid-liquid extraction inside the syringe, which could be classified as the third generation of flow techniques. The last part of the introduction deals with the automation of kinetic-catalytic methods using flow techniques, emphasizing the high potential of these methods for trace analysis and the low number of published papers on this subject. Research content. In this thesis, two flow techniques, MSFIA and MPFS, coupled to two sample pretreatment methods, gas diffusion and liquid-liquid extraction, and three detection techniques, anodic stripping voltammetry, conductometry and spectrophotometry, have been used to develop five automatic analytical systems. These systems have been applied to the determination of five inorganic analytes: cadmium, chromate, iodide, ammonium, and total inorganic carbon and applied to different environmental water samples with main focus on seawater. Involved in the development of these systems were the study of the used techniques and the finding of solutions for the problems related to the automation using flow techniques. Significant improvements of the analytical characteristics of the presented methods in comparison with similar ones reported in the literature are obtained. These improvement were an increase of the reproducibility and sensitivity of measurement, the decrease of reagent and sample consumption, the reduction of the analyzers’ sizes and instrumentation costs, and further, an increase of the automation degree of the analytical procedure, including: sample pretreatment, calibration and detection. The presented contributions are listed below: 1- A simple, economic, automated, and portable analyzer system based on MSFIA, which allows the determination of cadmium with anodic stripping voltammetry using a bismuth film coated screen printed electrode. (SPE-BiF-MSFIA) 2- An automatic MSFIA system for the determination of ammonium in naturals and seawaters in a very wide concentration range using gas diffusion and conductometric detection. (C-GD-MSFIA) 3- An automated and highly reproducible analyzer based on MPFS for the determination of total inorganic carbon and ammonium in seawaters using gas diffusion and conductometric detection. (C-GD-MPFS) 4- A fully automated in-syringe magnetic stirred-assisted dispersive liquid-liquid microextraction system for the spectrophotometric determination of chromate in natural waters. (In syringe-MSA-DLLME) 5- A microfluidic “Chip” conductor to be used in combination with MSFIA for the automated quantification of iodide in seawaters and pharmaceutical preparations using a kinetic-catalytic method characterized by a very low reagent and sample consumption. (CHIP-MSFIA-Catalytic) Conclusions Five new systems have been developed for the automatic determination of inorganic analytes of environmental interest. The use of the multi-commutated flow techniques MSFIA and MPFS has proven to be very useful for the automation of the analytical systems, coupling to different detection techniques, as well as sample pretreatment and kinetic-catalytic determinations. The developed systems have been confirmed to be efficient for the determination of inorganic analytes in complex sample matrices such as seawater, wastewater, or pharmaceutical preparations.

碩士
朝陽科技大學
環境工程與管理系碩士班
95
Abstract Electrochemical method has been applied as an innovative technique to investigate environmental substances. For measuring the amount of heavy metals, electrochemistry possesses advantages different from those of atomic adsorption spectrometry (AAS) and induced coupled plasma (ICP). Electrochemistry is easier to be controlled, smaller size of equipment, less capitalization, and more reliable analyses. As a consequence, Electrochemistry becomes an alternative among environmental-determining means. This research focuses on one of electrochemical methods, that is, the anodic stripping voltammetry (ASV). In the beginning, measuring experiments for standard copper solution were conducted in the laboratory to find appropriate operational factors and parameters according to voltage-current diagrams. Based on these experimental results, the feasibility of the ASV technique was evaluated. Afterwards, the ASV technique was served to determine the copper concentration in the contaminated soils and compared with the AAS. Based on the analytical data, the proper operational parameters include pH controlled at 3, 5 to 8 minutes for pre-concentration, and the copper concentration ranged from 100 ppb to 8 ppm. The linearity of analytical regression line is quite acceptable (R2＝0.9907) and the recurrence of data performs stable. However, the ASV application for measuring contaminated soils seems not applicable. In comparison with the analytical data obtained from AAS, the ASV analytical data are inconsistent. Only two sets of data by ASV analysis can fit the copper concentration by AAS among total 20 sets data. Most ASV data are lower than the detective limit of ASV or present much difference with AAS. In addition, the recurrence of ASV for real samples from contaminated sites is far from the theoretical expectation. This phenomenon implies analytical interruptions caused by some inorganic materials or metal ions. As a result, there needs to know interruption resources and species. Before we use the ASV technique to the real contaminated soils, the interruption problems should be overcame first.

碩士
國立清華大學
原子科學研究所
81
A two-step preconcentration procedure is proposed to be used in conjuction with differential pulse anodic stripping voltammetry for the determination of tracer metals in seawater. The two-step preconcentration involves extraction of trace metals from seawater with L,L-ethyl- enedicysteine diethylester (ECD) into chloroform followed by backextraction with a Hg(Ⅱ) solution. The extraction could concentration the trace metals by forming a chelate with ECD with a high enrichment factor obtained with the large phase volume ratio. The aqueous solution containing simply the enriched metals and some of the nonreacted Hg (Ⅱ) was taken for differential pulse anodic stripping voltammetry (DPASV) using a glassy carbon electrode.Anodic stripping voltammetry of the metals such as Zn,Cd,Pb and Cu were done directly in the backextraction solution, i.e. , Hg(Ⅱ). It should be worthwhile to note that the Hg(Ⅱ) solution used as the backextraction agent does not cause any interference in the anodic stripping voltammetry. Be- sides,the Hg(Ⅱ) can be used in situ as the source of mer- cury film to be coated on the glassy carbon electrode,ren- dering it as effective working electrode for DPASV.

Development and studies of new electrochemical methods for the detection of various biologically and environmentally relevant substances are the focus of this dissertation. A dual amperometric sensor, capable of the simultaneous, real-time determination of NO and O,2, has been developed and optimized. Many tests were performed in order to reduce cross-talking between the two sensors, and an electro-deposited polymer, poly-5-amino-1-naphthol, was shown to reduce the cross-talking to insignificant levels. The use of bismuth-based electrodes in the detection of various metals has been explored. A bismuth bulk electrode has been developed, optimized, and used for the individual and simultaneous determination of Pb(II), Cd(II), and Zn(II). The fundamental electrochemistry of several bismuth-based electrodes in the system used for Cr(VI) analysis has also been explored, and many interactions among the electrode material, ligand, and analyte were observed, particularly the formation of a soluble bismuth-ligand complex. Electrochemical analysis of Cr(VI) was attempted at all of the bismuth-based electrodes, with success at the thin bismuth film electrode. A series of surface modifications were made to the glassy carbon substrate, in an attempt to remove any co-adsorbed contaminants and to understand the sensitivity of the chromium detection process. Inevitably, it was found that the contaminating source was contaminants in the nitrogen gas used for solution deaeration. Upon switching to argon, detection became highly reproducible and showed strong linearity with the Cr(VI) concentration.

碩士
國立臺灣大學
化學工程學研究所
105
For trace metal analysis, electroanalytical methods offer several advantages over spectroscopies: simplicity, low cost and possibility of in-field application. Although the mercury thin film electrode and hanging mercury drop electrode are highly sensitive and selective, mercury is a highly toxic metal. Bismuth has been known as an environmentally friendly material which can be metabolized by human body, so nowadays bismuth thin film electrodes have become alternative material for electrochemical analysis. In this study, bismuth thin film electrodes were fabricated by electroplating bismuth on the glassy carbon electrode(GCE) in 0.1M acetate buffer solution (pH=4) containing 40ppm of Bi(III), and used in measuring of the concentration of Cd(II) by differential pulse anodic stripping voltammetry(DPASV). The effects of pre-electrodeposition potential, the concentration of Bi(III) in the analyte solution, and rotation of the working electrode have been investaged. The experimental results showed that the sensitivity of the electrode was increased about 76% with the pretreatment of glassy carbon electrodes by applying cyclic potential scans in 0.5M H2SO4. It was found that DPASV provided better Cd(II) detection in the analyte solution containing 1000ppb of Bi(III), and the best linear plot based on peak area in determination of 10 to 120ppb of Cd(II) occurred in the analyte solution containing 100ppb of Bi(III). The Bi thin film electrode on GCE offered good detection, even in non-deaerated solutions. From the investigation of pre-electrodeposition potential in DPASV, the maximum peak current was obtained at -1.1V (vs Ag/AgCl/KCl). It has been found in the experimental results that the preparation of Bi thin film electrode before anodic stripping voltammetry has been found unnecessarily, which can simplify the detection procedures. In the anodic stripping step, the electrode without rotation could keep the more stable current peaks than the electrode with rotation. The detection limit of Cd2+ is 0.2ppb.

Magister Scientiae - MSc
In this study multilayer graphene nanosheets was synthesize by oxidizing graphite to graphene oxide using H2SO4 and KMnO4 followed by reduction of graphene oxide to graphene using NaBH4. The graphene nanosheets were characterized by Fourier Transform Infrared (FTIR) and Raman spectroscopy, high resolution transmission electron microscopy (HRTEM), Scanning electron microscopy (SEM) and X-ray diffraction (XRD). HRTEM images showed that the multilayer graphene were obtained. The graphene was immobilized directly onto a glassy carbon electrode using the drop coating technique followed by the in situ deposition of mercury, bismuth or antimony thin films to afford graphene modified glassy carbon metal film electrodes (Gr-GC-MEs). The experimental parameters (deposition potential, deposition time, rotation speed, frequency and amplitude) were optimized, and the applicability of the modified electrode was investigated towards the individual and simultaneous determination of Zn2+, Cd2+ and Pb2+ at the low concentration levels (μg L-1) in 0.1 M acetate buffer (pH 4.6) using square wave anodic stripping voltammetry (SWASV). The detection limits values for the Gr-GC-HgE was 0.08, 0.05 and 0.14 μg L-1 for Zn2+, Cd2+ and Pb2+, respectively. The Gr-GC-BiE the detection limits for was 0.12, 0.22 and 0.28 μg L-1 for Zn2+, Cd2+ and Pb2+ while the detection limits for the Gr-GC-SbE was 0.1, 0.3 and 0.3 μg L-1 for Zn2+, Cd2+ and Pb2+, respectively. A Gr-GCE prepared without any binding agents or metal film had detection limits for Zn2+, Cd2+ and Pb2+ of 3.9, 0.8 and 0.2 μg L-1 for Zn2+, Cd2+ and Pb2+. Real sample analysis of which was laboratory tap water was performed using the Gr-GCMEs. Only Gr-GC-HgE was sensitive enough to detect metal ions in the tap water samples at the 3ppb level whereas, the GC-BiE and GC-SbE detected the metal ions at the 10 μg L-1 to 30 μg L-1 level.

Ph.D. (Chemistry)
Materials that are to be used as reference samples are frequently analysed using costly and sophisticated instrumentation, itself calibrated with similar certified standards. Analytical programmes using such instrumentation are only as accurate as the initial calibrations, and their poor results have led to the adoption by the United States National Bureau of Standards of definitive methods of analysis for the determination cf trace elements ...

碩士
國立中央大學
環境工程研究所
107
Cadmium is highly toxic and ingestion by humans may harm to humans, such as bone, kidney function, and respiratory system. At present, the method of analyzing heavy metals require pretreatment and long time so it cannot give the results of water quality promptly. However, electrochemical voltammetry is valued due to its advantages of convenient operation, low cost, simplicity and rapid analysis. In this study, determination of Cd(II) by square wave anodic stripping voltammetry using graphene oxide/single-walled carbon nanotubes/Bi2Te3 modified glassy carbon electrode was developed. First, the appropriate voltammetric scanning method is selected, and then the SWCNT/GO ratio was confirmed. The performance of the modified electrode in detecting Cd(II) at 120 s and 360 s was investigated after parameter optimization (electrolyte pH 5, deposition potential -1.1 V). The stability of the electrode was also evaluated. The results showed that the GO/SWCNT/Bi2Te3/GCE can successfully determine Cd(II) by SWASV. At a deposition potential of 120 s, the LOD is 0.99 μg/L; at a deposition potential of 360 s, the LOD is 0.14 μg/L, which is lower than the effluent standard (20–30 μg/L) and the drinking water standard (5 μg/L). Repeatability and reproducibility were 2.6% and 3.7%, respectively. Moreover, the electrode developed in this work is also free from the interference of Pb(II), Zn(II), Cr(III), Cr(VI), As(III), As(V) in water, but the stripping current of Cd(II) is easily affected by high concentration copper due to the low reduction potential of Cu(II). Finally, the analysis of Cd(II) in environmental waters confirmed the good recovery in tap water and groundwater.

Methods for the determination of trace elements in environmental and biological samples were developed and optimized. Parameters affecting sample introduction efficiency, matrix effects, sample throughput and tolerance to interfering species were evaluated for methods based on plasma spectrochemistry and electrochemistry. A method was developed for the determination of copper in the presence of β-2-microglobulin. A mass balance of copper was performed at the end of in vitro incubations which required method development to quantify copper in the liquid and solid portions of the incubation solutions, along with copper adsorbed and mass transferred into the walls of the incubation vessel. A flow injection method was developed to accommodate the small sample volume and high dissolved solids content to allow for the determination of copper by ICP-MS. A commercial introduction system was evaluated for the determination of trace elements in drinking waters and wastewaters by ICP-MS and ICP-OES. Parameters including increased throughput, reduced memory effects, increased stability and lower reagent consumption were evaluated as the system was successfully applied to U.S. EPA Methods 200.8 and 200.7, respectively. Particular attention was paid to the retention of mercury and sodium and long term stability during the analysis of samples containing high total dissolved salts. Results obtained with the new introduction system were compliant with EPA Methods 200.8 and 200.7 while increasing sample throughput two- or three-fold and significantly reducing memory effects. A method was developed for the enhancement of signals for trace elemental analysis by DRC-ICP-MS. Signal enhancement was evaluated as instrumental and reaction gas parameters were optimized. Background noise levels remained relatively unchanged as signal intensities were improved, resulting in improved signal to noise ratios. The developed method was successfully applied to the determination of gold in synthetic geological samples. A method was developed for the preconcentration and speciation of arsenic by anodic stripping voltammetry using ion exchange resins. Ion exchange and instrument parameters were optimized. The developed method was successfully applied to the determination of arsenic(III) and arsenic(V) in waters without interference from problematic species such as Cu(II). Suitable detection limits were obtained and the method was validated using a certified reference material.

Mestrado de dupla diplomação com a Université Libre de Tunis
The purpose of the current study was to quantify the concentrations of copper, cadmium, lead ions in wine using ASDPV with a lab-made graphite composite electrode. A first study involved analysis of a reversible redox solution of K3[Fe(CN)₆] with response surface methodology in order to verify the CV dependency with scan rate and potential step, as well the DPV dependency with scan rate, potential pulse and potential step. For the DPV analysis, the conditions selected were 0.03 V/s for the scan rate, 0.01 V for the step potential, and 0.04 V for the pulse potential. With these experimental conditions, the DPV data from a full factorial design using two concentration levels of the three heavy metals allowed to verify the independence between the calibrations of each metal. The analysis of 8 samples of Portuguese and Spanish wines by ETAAS allowed to verify that only copper levels were detected and quantified, obtaining Cu2+ concentrations varying between 0.011 and 0.535 mg/L. Considering the heavy metals trace levels, the ASDPV technique was selected, with the 4 min deposition step for standard calibration solution and sample solutions, which demanded an assisted digestion with HNO3 and H2O2. The ASDPV showed higher sensibility toward the copper (slope of 22 μA.L.mg-1), than cadmium (slope of 14.2 μA.L.mg-1) and lead (slope of 13.5 μA.L.mg-1). Only copper levels were measured in wine samples by ASDPV, within the range of 0.09 to 0.55 mg/L, being 0.91 times lower than those obtained by ETAAS. Overall, the cheap lab-made graphite composite working electrode allows to analyze simultaneously three heavy metals using the ASDPV technique. Its analytical performance allows considering its application in the voltammetric analysis of wines. However, there is space for improvement by optimizing the experimental procedure of solutions preparations for ASDPV analysis which will be addressed in future work.
O objetivo do presente estudo foi quantificar as concentrações dos iões cádmio, cobre e chumbo no vinho usando ASDPV com um elétrodo compósito de grafite feito em laboratório. Um primeiro estudo envolveu a análise de uma solução redox reversível de K3[Fe(CN)₆] com metodologia de superfície de resposta a fim de verificar a dependência da voltametria cíclica com a velocidade de varrimento e potencial de impulso, bem como a dependência da voltametria de impulso diferencial (DPV) com a velocidade de varrimento, potencial de impulso e potencial de incremento. Para a análise DPV, as condições selecionadas foram 0,03 V/s para a velocidade de varrimento, 0,01 V para o potencial de passo e 0,04 V para o potencial de incremento. Com estas condições experimentais, os dados de DPV de um desenho fatorial completo, utilizando dois níveis de concentração para os três metais pesados, permitiram verificar a independência entre as calibrações de cada metal. A análise de 8 amostras de vinhos Portugueses e Espanhóis pela ETAAS permitiu verificar que apenas foram detetados e quantificados os teores de cobre, obtendo concentrações de Cu2+ a variar entre 0,011 e 0,535 mg/L. Considerando os níveis vestigiais dos metais pesados, foi escolhida a técnica redissolução anódica (anodic stripping, AS) com DPV, com a etapa de deposição de 4 min para as soluções padrão de calibração e soluções de amostra, após sofrerem digestão assistida com HNO3 e H2O2. A ASDPV apresentou maior sensibilidade em relação ao cobre (declive de 22 μA.L.mg-1), do que para o cádmio (declive de 14,2 μA.L.mg-1) e chumbo (declive de 13,5 μA.L.mg-1). Apenas os teores de cobre foram medidos nas amostras de vinho por ASDPV, na faixa de 0,09 a 0,55 mg / L, sendo 0,91 vezes inferior aos obtidos pelo ETAAS. No geral, o elétrodo de trabalho compósito de grafite feito em laboratório permite analisar simultaneamente três metais pesados usando a técnica ASDPV. O seu desempenho analítico permite considerar a sua aplicação na análise voltamétrica de vinhos. No entanto, há espaço para melhorias, otimizando o procedimento experimental de preparação de soluções para análise de ASDPV que será abordado em trabalhos futuros.

Σκοπός της μελέτης ήταν ο ποσοτικός προσδιορισμός των ιχνοστοιχείων βαρέων μετάλλων του ψευδαργύρου, καδμίου και χαλκού στο υδατοειδές υγρό ασθενών με ψευδοαποφολίδωση και η μέτρηση του δυναμικού οξειδοαναγωγής στο υδατοειδές αυτών των ασθενών. Υλικό και μέθοδοι: Δείγματα υδατοειδούς υγρού ελήφθησαν κατά την εγχείρηση καταρράκτη από 14 ασθενείς με PEX σύνδρομο (7 άνδρες και 7 γυναίκες) και 21 ασθενείς με καταρράκτη αλλά χωρίς PEX (9 άνδρες και 12 γυναίκες). Τα δείγματα διατηρήθηκαν στους -24C μέχρι την ανάλυση. Τα επίπεδα των τριών μετάλλων και στις δύο ομάδες προσδιορίστηκαν, για πρώτη φορά στην Οφθαλμολογία, με τη μέθοδο της βολταμετρίας με χρήση ηλεκτροδίων υαλώδους γραφίτη με υμένιο υδραργύρου, ενδεικτικού ηλεκτροδίου λευκόχρυσου και αναφοράς Ag/AgCl. Εφαρμόσθηκε η τεχνική της ανοδικής βολταμετρίας απογύμνωσης με τετραγωνικούς παλμούς και έγινε σύγκριση των τιμών ανάμεσα στις δύο ομάδες. Η στατιστική επεξεργασία των αποτελεσμάτων έγινε με το Mann-Whitney test (p<0.05) Στη συνέχεια, κατά τον ίδιο τρόπο, δείγματα υδατοειδούς ελήφθησαν από 13 ασθενείς με PEX (7 άνδρες/6 γυναίκες) και 22 ασθενείς χωρίς PEX (7 άνδρες/15 γυναίκες). Η μέτρηση του δυναμικού οξειδοαναγωγής γινόταν αμέσως μετά την απόκτηση του κάθε δείγματος και για το σκοπό αυτό χρησιμοποιήθηκε για πρώτη φορά στην Οφθαλμολογία, ένα μικροηλεκτρόδιο λευκοχρύσου μαζί με ένα ενσωματωμένο ηλεκτρόδιο αναφοράς Ag/AgCl/KCl. Η στατιστική ανάλυση των αποτελεσμάτων έγινε με το t-test για ανεξάρτητα δείγματα (p<0.05). Αποτελέσματα: O Cu βρέθηκε στατιστικά σημαντικά χαμηλότερος στην PEX ομάδα σε σχέση με τη φυσιολογική ομάδα (p<0.05), ενώ ο Zn και το Cd δεν παρουσίασαν καμία συσχέτιση στο υδατοειδές υγρό ασθενών με ψευδοαποφολίδωση. Το δυναμικό οξειδοαναγωγής ήταν στατιστικά σημαντικά υψηλότερο στο υδατοειδές των ασθενών με PEX σύνδρομο. Συμπεράσματα: Στην παρούσα εργασία εφαρμόζεται για πρώτη φορά, η ανοδική βολταμετρία απογύμνωσης για τον προσδιορισμό στο υδατοειδές υγρό του Zn, Cd και Cu και η μέτρηση του δυναμικού οξειδοαναγωγής στο υδατοειδές. Τόσο τα στατιστικώς σημαντικά χαμηλότερα επίπεδα Cu στο υδατοειδές ασθενών με PEX, όσο και το υψηλότερο δυναμικό οξειδοαναγωγής στο υδατοειδές αυτών των ασθενών ενισχύουν την παθογενετική θεωρία του οξειδωτικού στρες του PEX συνδρόμου.
To determine the Zn, Cd and Cu concentrations in aqueous humor of patients with PEX syndrome and to evaluate the overall oxidative status of the aqueous in this group by measuring the reduction-oxidation (redox) potential in the aqueous samples. Material and methods: Samples from aqueous humor were collected during cataract extraction from 14 patients with PEX syndrome (7 male/7 female) and 21 patients without PEX (9 male/12 female). All samples were stored in -24C until analyzed. The levels of selected trace elements in both groups were assayed for the first time in the field of Ophthalmology, with anodic stripping voltammetry, using the square wave differential pulse technique. In this analytical procedure a glassy carbon mercury film electrode, a platinum indicator and a reference Ag/AgCl electrode were used. Finally the metal levels in all samples were compared between the two groups using the Mann-Whitney test (p<0.05). Similarly, samples were collected during cataract extraction from 13 patients (7 male/6 female) with PEX syndrome and 22 normal patients (7 male/15 female). A platinum electrode together with a reference electrode Ag/AgCl/KCl was used for the first time in Ophthalmology, for the measurement of the apparent redox potential in the aqueous humor. The independent samples t-test was used to compare aqueous redox potential between the study and control group. Statistical significance was set at 0.05. Results: Cu was found significantly lower in the PEX than in the control group (p<0.05), whereas Zn and Cd had no statistical differences between the two groups. The redox potential was found significantly higher in patients with PEX syndrome than in normal patients (p<0.05). Conclusions: In the present study we represent the first successful application of ASV in eye research for the determination of aqueous Zn, Cd and Cu concentrations and the meauserment of aqueous redox potential. The significantly lower Cu concentrations and the higher redox potential in aqeous humor of PEX syndrome support the role of increased oxidative stress in the development of PEX.

碩士
文化大學
應用化學系
85
Speciation of Zinc,Cadmium and Lead ions in the surface water of erhjen river,estuarine and coastal areas is studied by differential pulse anodic stripping voltammetry (DPASV). Colloidal and truly dissolved phases trace metals from the water of a highly polluted estuarine and coastal environment (The Erhjen river) have been separated by a cross-flow ultrafiltration device.The distributions of Cadmium,Zinc and Lead between colloid and truly solution were 17.7%~27.4% and 72.6%~82.3% ,42.1%~63.3% and 36.7%~57.9% and 29.3%~50.1% and 49.9%~70.7% respectively.Generally ,truly solution fraction was the dominant species in water of this study .complexing capacities were reducing from river to coastal area. The result indicated that Erhjen river abounds with organic ligand that reduces as it flows toward the sea,

Przygotowanie próbki do analizy specjacyjnej jest trudnym zadaniem, praktycznie każda próbka i każdy analit wymagają osobnych scenariuszy analitycznych. Arsen, chrom oraz tal należą do grupy pierwiastków znajdujących się na liście priorytetów badawczych Amerykańskiej Agencji Ochrony Środowiska (US EPA). Analiza specjacyjna szeregu pierwiastków jest istotnym elementem nowoczesnego monitoringu środowiska, ponieważ ich toksyczność, mobilność, czy biodostępność zależy od stopnia utlenienia oraz formy chemicznej. Do najbardziej toksycznych form As należą połączenia nieorganiczne, natomiast organiczne związki arsenu są nietoksyczne. Związki Cr(III) są mniej rozpuszczalne i bardziej stabilne w naturalnym wodnym środowisku, podczas gdy związki Cr(VI) są bardziej rozpuszczalne i mobilne. Związki Tl(III) są bardziej toksyczne niż związki Tl(I). Woda, jako abiotyczny element środowiska naturalnego odpowiada za transport zanieczyszczeń oraz zmianę form specjacyjnych pierwiastków. Wodę można podzielić na frakcję rozpuszczoną, która odpowiada za transport zanieczyszczeń oraz fazę zwieszoną (SPM), która jest odpowiedzialna za współstrącanie form chemicznych As, Cr oraz Tl. Zebrano próbki wód zawierających związki powierzchniowo czynne oraz sprawdzono powinowactwo wybranych form As, Cr i Tl do zawiesiny (SPM). Formy specjacyjne rozdzielono i zatężono z wykorzystaniem ekstrakcji do fazy stałej. Zastosowano różne sorbenty m.in. SGX C18 modyfikowany pyrolidynoditiokarbaminanem amonu (APDC) oraz tlenek glinu modyfikowany dodecylosiarczanem sodu (SDS). Sprawdzono możliwość wydzielania As(III), Cr(III) i Tl(III) z wody. Jednak tylko dla Tl(III) zaproponowano kompletną procedurę wydzielenia i zatężenia Tl(III) z matrycy wody. Następnie sprawdzono możliwość wykorzystania fotokatalizatorów tritlenku wolframu oraz tritlenku diżelaza do rozłożenia surfaktantów przed analizą specjacyjną. Zaproponowano różne warstwy aktywne składające się z fotokatalizatorów tlenków wolframu i żelaza. Płytki te oceniono podczas rozkładu SDS oraz Tritonu X-114, gdzie sensorem był układ elektroda rtęciowa i oznaczanie śladowych ilości Pb(II). Wybrane fotowarstwy sprawdzono w degradacji związków organicznych przed analizą specjacyjną arsenu, chromu i talu. Opracowano pełną procedurę od pobrania próbki do analizy związków As i Tl w wodach o dużej zawartości związków powierzchniowo czynnych. Scenariusz analityczny oparty na fotokatalizie mógłby być włączony w nowoczesną analizę środowiskową.
Sample preparation for speciation analysis is a difficult task, practically each sample and each analyte requires unique analytical scenarios. As, Cr i Tl belong to the group of elements included in the list of research priorities of the American Environmental Protection Agency (US EPA). Toxicity, mobility, or bioavailability of many elements depend on their oxidation state and chemical form. For this reason speciation analysis is an important element of modern environmental monitoring. The most toxic forms of As are inorganic compounds, while organic arsenic compounds are non-toxic. Cr(III) compounds are less soluble and more stable, while Cr(VI) compounds are more soluble and mobile in the natural aqueous environment. Tl(III) compounds are more toxic than Tl(I) compounds. Water, which is an abiotic element of the environment, is responsible for transport of pollutants and changes of the speciation forms of elements. Water can be divided into two phases: dissolved phase which is responsible for the transport of pollutants and suspended particulate matter (SPM) which is responsible for co-precipitation of chemical forms of As, Cr and Tl. Water samples containing surface active compounds were collected. The affinity of selected As, Cr and Tl forms for SPM was checked. The speciation forms were separated and preconcentrated using solid phase extraction. Various sorbents have been applied, e.g. SGX C18 modified with ammonium pyrolidinedithiocarbamate and alumina modified with sodium dodecyl sulphate (SDS). The possibility of simultaneous separation of As(III), Cr(III) and Tl(III) from water was tested. However, a complete procedure was developed only for separation and preconcentration of Tl(III) from the water matrix. Next, the possibility of application of photocatalysts: tungsten and iron oxides for decomposition of surface-active compounds before the speciation of As, Cr and Tl was tested. Different active layers consisting of tungsten and iron oxides have been proposed. These active layers were evaluated during the decomposition of SDS and Triton X-114. Decomposition efficiency was evaluated on the basis of voltammetric determination of trace amounts of Pb(II) with a mercury electrode, which is very sensitive to interferences from organic compounds. Selected photolayers were tested in the degradation of organic compounds before speciation analysis of arsenic, chromium and thallium. A complete procedure (from sampling to determination) for analysis of As and Tl compounds in waters with high content of surfactants was developed. Analytical scenarios based on photocatalysis could be included in the modern environmental monitoring.

Объектом исследования являются бактерии Staphylococcus aureus в модельных суспензиях. Цель работы— апробация разработанных алгоритмов определения Staphylococcus aureus с использованием электрохимической системы на основе бесферментных электрохимических иммуносенсоров в модельных суспензиях. Определение чувствительности микробной флоры к антибактериальному препарату.В процессе работы должны быть проведены исследования синтезированных наночастиц магнетита, изучен характер электропревращений модифицированных наночастиц. Должен быть осуществлен выбор рабочего электрода и оптимальных условий анализа для количественного определения Staphylococcus aureus в модельных суспензиях. Должна быть проведена апробация разработанных алгоритмов по определению Staphylococcus aureus в модельных образцах. Определена чувствительность микробной микрофлоры к антибактериальному препарату мазь «Новокомб – 50%». В результате исследования были синтезированы наночастицы магнетита (Fe3O4), наличие полимерного покрытия подтверждено методом ИК - спектроскопии. В результате проведенных экспериментов был получен электрохимический аналитический отклик от модифицированных наночастиц магнетита. Были выбраны оптимальные условия регистрации аналитического сигнала. В качестве рабочего электрода был выбран планарный платиновый электрод, в качестве метода иммобилизации - метод физической сорбции антител на рабочую зону электрода. Был получен электрохимический отклик от иммунокомплекса антитело-бактерия, меченая наночастицами магнетита. Были выбраны оптимальные условия проведения количественного определения Staphylococcus aureus в модельных суспензиях. При данных условиях была выполнена оценка результатов в отношении таких показателей, как воспроизводимость и специфичность. По результатам апробации алгоритмов на модельных образцах было выявлено, что результаты данного метода коррелируют с методами ИФА и бактериального посева. Точность метода с использованием электрохимического иммуносенсора удовлетворительная. Данный метод может быть рекомендован для определения чувствительности микробной флоры к антибактериальным препаратам при их разработке, исследовании и на этапах серийного производства и обращения Основные конструктивные и технико-эксплуатационные показатели: предел обнаружения для бактерий Staphylococcus aureus составил 8.7 КОЕ/мл. Относительное стандартное отклонение не превышает 10%.Эффективность метода определяется возможностью его применения для определения чувствительности микробной флоры к антибактериальным препаратам при их разработке, исследовании и на этапах серийного производства и обращения.
Object of research are the bacteria Staphylococcus aureus in model suspensions. The purpose of testing the developed algorithms work- determining Staphylococcus aureus using electrochemical systems based on electrochemical besfermentnyh immunosensors in model suspensions. Determination of the sensitivity of the microbial flora to antibacterial preparatu.V during operation should be studied synthesized nanoparticles of magnetite, studied character elektroprevrascheny modified nanoparticles. Selection is to be made the working electrode and optimal assay conditions for quantitative determination of Staphylococcus aureus in model suspensions. It must be carried out testing of the developed algorithms to identify Staphylococcus aureus in model samples. Determine the sensitivity of the microbial microflora antimicrobial ointment "Novokomb - 50%." The study nanoparticles of magnetite (Fe3O4) were synthesized, the presence of the polymer coating was confirmed by IR - spectroscopy. As a result of the experiments was obtained from the electrochemical analytical response modified magnetite nanoparticles. optimal conditions for the registration of the analytical signal were selected. The working electrode was selected planar platinum electrode, as a method of immobilization - the method of physical adsorption of antibodies to the working electrode area. electrochemical response by the bacterium-antibody immunocomplex, labeled magnetite nanoparticles was obtained. the optimal conditions were selected quantitative determination of Staphylococcus aureus in model suspensions. Under these conditions, evaluation of the results was carried out in relation to indicators such as reproducibility and specificity. According to the results of testing of algorithms to model samples it was found that the results of this method correlate with the ELISA and bacterial seeding. Accuracy of the method using an electrochemical immunosensor satisfactory. This method can be recommended for the determination of the sensitivity of the microbial flora to antibiotics when they are developing, researching and on the stages of mass production and circulation of basic design and technical and operational parameters: detection limit for bacteria Staphylococcus aureus was 8.7 CFU / ml. The relative standard deviation does not exceed 10% g? O FIG method determined by the possibility of its application for the determination of the sensitivity of the microbial flora to antibiotics when they are developing, researching and on the stages of mass production and circulation.