This work focuses on optimization and application of voltammetric methods for determination of 5-nitroquinoline in model samples of drinking and river water using carbon film electrode (CFE). The advantages of carbon film electrode are primarily its wide potential window in both cathodic and anodic regions and also low environmental stress compared to mercury electrodes. In this contribution, CV and AdSV were used to observe electrochemical processes. For determination of 5-nitroquinoline DPV and FIA were used. Solid phase extraction was investigated as a method for preliminary separation and preconcentration for DPV. Determination of 5-nitroquinoline at CFE is based on cathodic reduction of nitrogroup. This work demonstrates the application of carbon film electrode for determination of 5-nitroquinoline in submicromolar concentrations in model samples of water.

Tellurium and bismuth are non-biogenous elements, which can be accumulated in human body. The aim of this work is focused on the determination of these elements by the electrochemical hydride generation with non-membrane electrolytic cell with quartz tube - atomic absorption spectrometry. The first step of the work was to optimize parameters for the continuous setup measurements and to obtain its figures of merit. After this, the arrangement with most suitable conditions for determination of these elements was converted to the flow injection setup (FIA) and all experimental parameters were again optimized and its figures of merit were obtained. The conditions of hydride generation were studied for platinum, lead and silver cathodes with hydrochloric and sulphuric acids and their sodium salts as electrolytes. The optimizations of the FIA setup were performed on platinum cathode in hydrochloric acid for bismuth and on lead cathode in sulphuric acid for tellurium. The limit of detection achieved for the generation of tellurium hydride was 1.1 ppm with a linear range up to 20 ppm; for the bismuth hydride the limit of detection was 9.5 ppm and limit of linearity 50 ppm. Keywords Bismuth, tellurium, electrochemical hydride generation, atomic absorption spectroscopy, flow injection analysis

This diploma thesis deals with the determination of creatinine using a combination of flow injection analysis (FIA) or high-performance liquid chromatography (HPLC) with pulse amperometry, an electrochemical technique based on the application of potential pulses on a gold working electrode. The determination was performed in a basic environment of borate buffer with creatinine concentration of 1∙10-4 mol∙l-1 . The lenght of the cleaning and activation pulse was optimized as well as the pH of the running buffer. A cleaning pulse of +1.8 V was first applied to the electrode for 100 ms, then an activation potential of -0.5 V was applied for 150 ms and then a measuring potential of +0.2 V for 300 ms. The optimal pH was selected as pH=9,4. Methanol and acetonitrile were added to the borate buffer to test whether creatinine could be determined in presence of these organic solvents and whether flow injection analysis could be transformed into HPLC. Methanol in the system caused peak deformation, acetonitrile did not cause the peak deformation in the system, at higher contents the baseline was destabilized. Furthermore, the calibration dependence in the range of concentrations from 2.5∙10-4 mol∙l-1 to 5∙10-6 mol ∙ l-1 was measured using PAD in combination with FIA. At higher concentrations, peaks splitted....

[pt] Uma sonda fotoluminescente do tipo turn-off foi avaliada para a detecção de Hg(2+) usando pontos quânticos de grafeno (GQDs). Diferentes nanopartículas de carbono fotoluminescentes foram preparadas usando a abordagem bottom-up, usando ácido cítrico ou ácido cítrico misturado com algum composto contendo enxofre (tioureia, tioacetamida ou glutationa). Dispersões desses GQDs foram comparadas em termos de comportamento fotofísico na presença de Hg(2+). Observou-se que as nanopartículas preparadas com ácido cítrico e tioureia (GQDs- TU) apresentaram melhor perfil de supressão fotoluminescente (resposta analítica) na presença de Hg(2+). As condições experimentais foram ajustadas para o melhor perfil de resposta e para obter os parâmetros analíticos de mérito. Um estudo para avaliar possíveis interferências na presença de outros íons de metais pesados além de íons alcalinos e alcalino-terrosos, comumente presentes em amostras de água natural. A curva analítica normalizada (concentração L0/L versus Hg(2+) foi linear (R(2) = 0,998) até 0,20 microgramas L(-1). O limite de quantificação (LOQ) foi de 10 microgramas L(-1) e o limite de detecção (LOD) foi de 3 microgramas L(-1) para o ensaio em batelada. Além disso, a estratégia proposta para a determinação indireta de Hg(2+) foi adaptada para um sistema de análise por injeção em fluxo (FIA). Após a otimização do ensaio, com a faixa linear cobrindo o intervalo até 900 microgramas L(-1) (R(2)= 0,999), os valores de LOD e LOQ foram 24 microgramas L(-1) e 80 microgramas L(-1), respectivamente. A recuperação na amostra simulada de água fortificada foi de 99,4 por cento mais ou menos 1,2. / [en] A photoluminescent turn-off probe was evaluated for the detection of Hg(2+) based on graphene quantum dots (GQDs). Different photoluminescent carbon nanoparticles were prepared using the bottom-up approach, with citric acid and with citric acid mixed with some sulfur compound (thiourea, thioacetamide or glutathione). Dispersions of these GQDs were compared in terms of photophysical behavoior in the presence of Hg(2+) . It was observed that the nanoparticles prepared with citric acid and thiourea (GQDs-TU) presented a better linear photoluminescent suppression (analytical response) in the presence of Hg(2+). Experimental conditions were adjusted to improve analytical response and to obtain analytical figures of merit. A study to evaluate potential interferences in the presence of other heavy metal ions and alkaline and alkaline-earth ions, commonly present in natural water samples. The normalized analytical curve (L0/L versus Hg(2+) concentration) was linear (R(2) = 0.998) up to 0.20 micrograms (L-1). The limit of quantification (LOQ) was 10 micrograms L(-1) and the limit of detection (LOD) was 3 micrograms L(-1) for the batch assay. In addition, the proposed strategy for indirect determination of Hg2+ was applied in a flow injection analysis system (FIA). After optimization of the assay, linear range covered a range up to 900 micrograms L(-1) (R(2) = 0.999) with LOD of 24 micrograms L(-1) and LOQ of 80 micrograms L(-1). The recovery in the fortified water sample was 99.4 percent.

This diploma thesis is focused to the determination of procaine using flow injection and sequential injection analysis coupled with spectrophotometric detection. This determination is based on the reaction of procaine with a colouring agent, 1,2-naphthoquinone-4-sulfonic acid. An orange coloured product is formed, which is determined spectrophotometrically at the wavelength 484 nm. The high of the absorption signal of the product is directly proportional to the concentration of procaine. The aim of this work was to optimize the parameters of both methods of flow analysis so that the limit concentration of procaine can be as low as possible and at the same time, high sensibility is achieved. The next step was to apply these methods on the determination of procaine in real samples. It was found that in flow injection analysis, the absorbance of procaine hydrochloride obeys Beer's law for concentrations from 2.5 to 120 µg/ml. The linear regression equation of calibration graph was y = 0.0059x - 0.0051, with a linear regression correlation coefficient 0.9993. Limit of detection was 0.72 µg/ml. Effects of standing time (stopped-flow), flow rate, concentration of colouring agent, pH and the volume of the sample loop have been examined and optimized. It was also found that in sequential injection...

This master's thesis is focused on the determination of 6-thioguanine (6-T) by DC voltammetry (DCV), differential pulse voltammetry (DPV) and flow injection analysis with electrochemical detection (FIA-ED) on a boron doped diamond electrode (BDDFE). The optimum conditions for determination of 6-T were found and under these conditions, concentration dependences were measured and the limits of quantification (LOQ) were calculated for each method. Medium of 60% methanol and phosphate buffer (PB) pH 2,0 was chosen as optimum for DCV and DPV determination of 6-T at BDDFE. For both DCV and DPV, the linear concentration dependences were obtained in concentration ranges of 6-T from 2 µmol·l-1 to 10 µmol·l-1 with LOQ 0,9 µmol·l-1 for DCV and 1,5 µmol·l-1 for DPV. Lower LOQ was achieved in PB pH 2,0, where LOQ was 0,6 µmol·l-1 for both DCV and DPV, but the problem was lower repeatability. In PB pH 2 6-T was determined by DCV in drinking and river water with LOQ 1,3 µmol·l-1 in both drinking and river water. The possibility of solid phase extraction was investigated as a method for preliminary separation of 6-T from urine. For FIA under optimized conditions (polarization potential 1300 mV, flow rate 5 ml·min1 and sample volume 50 µl) the linear concentrations dependences were obtained in concentration ranges...

Análise cinética diferencial explora diferenças em taxas reacionais entre os analitos e um sistema reacional comum; etapas de separação prévia dos analitos podem então ser prescindidas. Sistemas de análise por injeção em fluxo (FIA) se afiguram como uma ferramenta importante para métodos envolvendo essa estratégia, pois permitem um controle preciso da dispersão de reagentes / amostras e da temporização. O objetivo deste trabalho foi então explorar estes dois aspectos favoráveis visando a determinação simultânea de cobre e de níquel, a partir de suas reações com o reagente cromogênico 5-Br-PADAP. Três alíquotas de amostra eram simultaneamente inseridas, por meio de um injetor proporcional, no fluxo transportador reagente (5-Br-PADAP 75 mg L-1 + sistema tampão 0,5 mol L-1 em ácido acético / acetato, pH 4,7) de um sistema FIA em linha única. Durante o transporte em direção ao detector, as zonas estabelecidas se coalesciam, originando uma zona complexa que era monitorada a 562 nm. Os valores locais máximos e mínimos da função concentração / tempo obtida eram considerados para calibração multivariada utilizando a ferramenta quimiométrica PLS-2 (partial least squares - 2). A concentração do reagente, a capacidade tampão, a temperatura, a vazão, os comprimentos do percurso analítico e das alças de amostragem, bem como a distância inicial entre as zonas de amostra estabelecidas foram avaliados para construção dos modelos matemáticos. Estes foram criados a partir de 24 soluções-padrão mistas de Cu2+ e Ni2+ (0,00-1,60 mg L-1 em HNO3 a 0,1% v/v). Duas variáveis latentes foram suficientes para capturar > 98 % das variâncias inerentes ao conjunto de dados e erros médios das previsões (RMSEP) foram estimados em 0,025 e 0,071 mg L-1 para Cu e Ni, salientando a boa precisão do modelo de calibração. O sistema proposto apresenta boas figuras de mérito: fisicamente estável, quando mantido em operação por quatro horas ininterruptas, consumo de 314 \'mü\'g 5-Br-PADAP por amostra, frequência analítica de 33 amostras por hora (165 dados, 66 determinações) e erros nas leituras em sinais de absorbância tipicamente < 5%. Entretanto, verificou-se a inexatidão das previsões efetuadas pelo modelo proposto, quando comparadas aos resultados obtidos por ICP OES. A partir deste fato, tornam-se necessários maiores estudos referentes a este tipo de matriz, bem como de técnicas de mascaramento dos possíveis interferentes presentes / Differential kinetic analysis exploits the differences in reaction rates between the analytes and a common reactant system; prior steps of analyte separation can then be waived. Flow-injection systems (FIA) are considered as an important tool for methods involving such a strategy because they allow precise control of sample / reagent dispersion and timing. The aim of this work was then to exploit these two favorable aspects for the simultaneous determination of copper and nickel using the 5-Br-PADAP chromogenic reagent. Three sample aliquots were simultaneously inserted by means of a proportional injector into reagent carrier stream (75 mg L-1 5-Br-PADAP + 0.5 mol L-1 acetic acid / acetate, pH 4.7) of a single-line FIA system. During transport towards detection, the established zones coalesce themselves, resulting in a complex zone that was monitored at 562 nm. The local maximum and minimum values of the concentration / time obtained function were considered for multivariate calibration using the PLS-2 (partial least squares - 2) chemometric tool. The reagent concentration, buffering capacity, temperature, flow rate and lengths of the analytical path, sampling loops and initial distance between plugs were established and evaluated for the construction of mathematical models. To this end, 24 Cu2+ and Ni2+ (0.00 - 1.60 mg L-1, also 0.1% v/v HNO3) mixed standard solutions were used. Two latent variables were enough to capture > 98% of the variance inherent in the data set and average prediction errors (RMSEP) were estimated as 0.025 and 0.071 mg L-1 for Cu and Ni, emphasizing the good precision the calibration model. The proposed system presents good figures of merit: physical stability when kept in operation for four uninterrupted hours, consumption of 314 \'mü\'g 5-Br-PADAP per sample, sample throughput of 33 h-1 (165 data, 66 determinations) and error readings in absorbance signals typically <5%. However, inaccuracy of the predictions made by the proposed model when compared to results obtained by ICP OES was noted. Thus, further studies involving this type of matrix, as well as masking techniques of potential interferences present, are recommended

Estudos foram conduzidos relativamente ao desempenho dos sistemas de análises em fluxo quando configurados como sistemas inteligentes, associados às técnicas de calibração multivariada ou empregando nanocristais como sensibilizadores. Ainda, melhorias relacionadas às modificações dos fluxos foram avaliadas, especialmente no que se refere à diálise em linha. Neste sentido, foi proposta uma nova estratégia para implementar determinações simultâneas de ferro e vanádio em ligas metálicas envolvendo cinética diferencial. O método baseava-se nas diferentes influências exercidas por Fe2+ e por V4+ na taxa de oxidação de íons iodeto por íons Cr6+ sob condições ácidas. Três diferentes alíquotas de amostra eram inseridas em um fluxo transportador / reagente de KI, confluindo posteriormente com um fluxo de K2Cr2O7. A sobreposição entre as três zonas de amostra estabelecidas resultava em uma zona de amostra complexa com diversos valores de absorbância. Medidas realizadas nos pontos de máximos e minímos do sinal registrado eram mais precisas e continham informações acerca dos diferentes estágios de desenvolvimento da reação e de diferentes condições de concentrações. Em outra estratégia, um sistema MPFS inteligente foi proposto para a determinação turbidimétrica sequencial de sulfato e cloreto em águas naturais. Ambos os métodos foram implementados no mesmo módulo de análises, proporcionando facilidades relativas ao: preparo de amostra em linha; adição de íons sulfato ou cloreto ao meio reacional para melhoria das condições de supersaturação; decisão em tempo real acerca da necessidade ou não da próxima análise. Inicialmente, determinava-se a concentração de cloreto presente na amostra, e este resultado era comparado com um valor pré-determinado. Se este fosse superior, a amostra era analisada novamente visando à determinação de sulfato. Caso contrário, uma nova amostra era analisada. A estratégia resultou em aumento da velocidade analítica e em boas figuras de mérito analítico. Estudos relativos à natureza do fluxo foram conduzidos avaliando-se o desempenho dos fluxos pulsados provenientes de bombas solenóide em relação à eficiência do transporte de massas, dispersão da zona de amostra relacionada com a mudança de sentido do fluxo e eficiência do processo de diálise quando comparados aos fluxos tipicamente laminares. Embora fosse observada a presença de vórtices, o número de Reynolds experimentalmente obtido demonstrou que o fluxo resultante não era turbulento. Porém seu perfil exibia características de mescla turbulenta, melhorando assim o desempenho relativo ao transporte de massas e redução da dispersão da zona de amostra. Entretanto, beneficios relativos a melhorias no processo de diálise foram ausentes devido provavelmente à alta pressão exercida dentre da câmara de diálise, com consequente deformação dos poros da membrana. Nestas situações, um sistema de análises híbrido (com fluxo laminar e mescla turbulenta) seria fortemente recomendado. Finalmente, a implementação de nanocristais quantum dots (QDs) como sensibilizadores em um sistema MPFS envolvendo reação quimioluminescente foi proposta para a determinação de glipizida e gliclazida em formulaçoes farmacêuticas. O método fundamentava-se na oxidação dos íons S2- por Ce4+ em meio ácido. Na presença dos analitos, a intensidade da radiação emitida era inibida. A influência do diâmetro médio dos nanocristais foi avaliada, e os critérios utilizados para o dimensionamento do sistema foram a repetibilidade, a reprodutibilidade e a sensibilidade analítica. Os analitos foram quantificados no mesmo módulo de análises, e boas figuras de mérito analítico foram verificadas. Os resultados obtidos se apresentaram concordantes com aqueles obtidos pela Farmacopéia Britânica / Studies focusing on performance of intelligent analytical flow systems, association with multivariate calibration or use of nanocrystals as sensitizers were carried out. Moreover, improvements related to modifications in flow pattern were evaluated with emphasis to in-line dialysis. To this end, a strategy for implementing simultaneous determinations of iron and vanadium in alloys relying on differential kinetics was proposed. The method was based on the influence of Fe2+ and V4+ on the rate of iodide oxidation by Cr6+ under acidic conditions. Three different plugs of the sample were sequentially inserted into an acidic KI reagent carrier stream, and a confluent K2Cr2O7 solution was added downstream. Overlap between the established plugs led to a complex sample zone with several regions of maximal and minimal absorbance values. Measurements performed on these regions were more precise and revealed the different degrees of reaction development. In another strategy, an intelligent MPFS was proposed for sequential turbidimetric determination of sulphate and chloride in natural waters. Both methods were implemented in the same manifold, providing facilities for: in-line sample cleanup; addition of low amounts of sulphate or chloride ions to the reaction medium for improving supersaturation conditions and real-time decision on the need for next assay. The sample was initially run for chloride determination, and the analytical signal was compared with a preset value. If higher, the sample was run again, now for sulphate determination. Otherwise, next sample was assayed. The strategy led to an increased sample throughput and good analytical figures of merit. Studies focusing on the flow pattern were carried out aiming at the evaluation of the influence of the pulsed flows delivered by solenoid pumps in relation to the efficiency of mass transfer, dispersion related to changes in flow direction of the sample zone and dialysis process as compared with typical laminar flow. Although the establishment of vortices were noted, the experimentally obtained Reynolds number showed that a turbulent flow was not established. Its pattern exhibited characteristics which improved the performance due to the enhanced radial mass transport inherent in turbulent mixing. Comparatively to laminar flow, beneficial aspects were noted in relation to sample dispersion and mass transfer. In relation to dialysis efficiency however process the benefits were not noted probably due to the high pressure inside the dialysis chamber, with consequent membrane pore deformation. In this situation, a hybrid flow analysis system (with laminar flow and turbulent mixing) might be recommended. Implementation of quantum dots nanocrystals (QDs NC) as sensitizers in a MPFS with chemiluminometric detection was proposed for the determinations of gliclazide and glipizide in pharmaceutical formulations. The method relied on the oxidation of sulphite by Ce4+ in acidic medium and, in the presence of the analytes, the emitted radiation of the Ce4+-SO3 2--CdTe QDs system was inhibited. Influence of crystal size was investigated, and the criteria for system optimization were the analytical repeatability, reproducibility and sensitivity. Both analytes were quantified in the same manifold, resulting in good analytical figures of merit. The results were in fairly good agreement with those obtained by the British Pharmacopoeia reference method

No Brasil os dados sobre a utilização dos sulfitos pela indústria de alimentos e pesquisas sobre o seu consumo são escassos. Sendo assim, o objetivo desta pesquisa foi avaliar o nível de sulfitos em sucos de frutas e estimar seu consumo por escolares de 5ª. a 8ª. séries de escolas públicas, do ensino fundamental, do município de São Caetano do Sul-SP, Brasil. Foi aplicado questionário de freqüência de consumo de alimentos (QFCA) em 313 escolares, sendo 56,9 % do sexo feminino e 43,1 % do sexo masculino, com média de idade de 14,7 anos. Os alimentos sulfitados mais consumidos foram os néctares ou sucos de frutas, o açúcar refinado, as batatas fritas congeladas, o coco ralado, o suco de caju e as frutas secas e cristalizadas. Considerando os limites máximos permitidos (LMP) pela legislação brasileira, o consumo de SO2, em mg SO2/kg pc/dia, foi de 0,12 mg SO2/kg pc/dia, sendo que este valor médio corresponde a 17% da IDA (0,7 mg SO2/kg pc/dia). Já os resultados das análises dos sucos de frutas demonstram que a análise por injeção em fluxo (Flow injection analysis - FIA) modificada obteve resultados de sulfitos nas amostras analisadas com menor variação do que aqueles obtidos pelo método Monier-Williams (M-W) otimizado, e que nenhuma amostra ultrapassou os LMP. / In Brazil there are no data on use of sulphites by the food industry and research on their consumption by population. Thus, the objective of this research was to evaluate sulphites in fruits juices and estimate intake sulphites in a group of 5th 8th schoolchildren of public schools in São Caetano do Sul-SP, Brazil. It was applied a food frequency questionnaire (FFQ) at 313 schoolchildrens (56.9% female, 43.1% male and average age 14.7 years). Sulphited products identified were fruits juices, sugar, frozen chips, grated coconut, cashew juice and dried fruits. Considering maximum permitted levels (MPL) stabilished by Brazilian legislation, none of the students exceeded the ADI of 0.70 mg SO2/kg bw/day, with average of consumption of 0.12 mg SO2/kg bw/day (17 % of the ADI). The results of the fruits juices analysis demonstrated flow injection analysis (FIA) modified obtained better results than optimized Monier-Williams method (M-W) and no sample exceeded the MPL.

Shelf seas represent an important source of iron (Fe) to the open ocean. Additionally, shelf seas are highly productive environments which contribute to atmospheric carbon dioxide drawdown and support large fisheries. The work presented in this thesis describes the seasonal cycle of Fe in the Celtic and Hebridean Shelf Seas, and determines the physico-chemical speciation of Fe supplied from oxic margins. The results from repeated field surveys of the central Celtic Sea showed a nutrient type seasonal cycling of dissolved Fe (< 0.2 µm; dFe), which is surprising in a particle rich shelf system, suggesting a balance of scavenging and remineralisation processes. Coincident drawdown of dFe and nitrate (NO3-) was observed during the phytoplankton spring bloom. During the bloom, preferential drawdown of soluble Fe (< 0.02 µm; sFe) over colloidal Fe (0.02-0.2 µm; cFe) indicated greater bioavailability of the soluble fraction. Throughout summer stratification, it is known that NO3- is drawn down to < 0.02 µM in surface waters. This study revealed that both dFe and labile particulate Fe (LpFe) were also seasonally drawn down to < 0.2 nM. Consequently, it is hypothesised that the availability of Fe seasonally co-limits primary production in this region. At depth both dFe and NO3- concentrations increased from spring to autumn, indicating that remineralisation is an important process governing the seasonal cycling of dFe in the central Celtic Sea. In spring, summer and autumn, distinctive intermediate nepheloid layers (INL) were observed emanating from the Celtic Sea shelf slope. The INLs were associated with elevated concentrations of dFe (up to 3.25 ± 0.16 nM) and particulate Fe (up to 315 ± 1.8 nM) indicating that they are a persistent conduit for the supply of Fe to the open ocean. Typically > 15% of particulate Fe was labile and 60-90% of dFe was in the colloidal fraction. Despite being < 50 km from the 200 m isobath, the concentration of dFe was < 0.1 nM in surface waters at several stations. Broadly, the concentration of nutrients in surface waters described an oligotrophic environment where co-limitation between multiple nutrients, including Fe, appears likely. Over the Hebridean shelf break, residual surface NO3- concentrations (5.27 ± 0.79 µM) and very low concentrations of dFe (0.09 ± 0.04 nM) were observed during autumn, implying seasonal Fe limitation. The dFe:NO3- ratio observed is attributed to sub-optimal vertical supply of Fe relative to NO3- from sub-surface waters. In contrast to the shelf break, surface water in coastal regions contained elevated dFe concentrations (1.73 ± 1.16 nM) alongside low NO3-. Seasonal Fe limitation is known to occur in the Irminger and Iceland Basins; therefore, the Hebridean shelf break likely represents the eastern extent of sub-Arctic Atlantic seasonal Fe limitation, thus indicating that the associated weakening of the biological carbon pump exists over a wider region of the sub-Arctic Atlantic than previously recognised. These key findings demonstrate that the availability of Fe to phytoplankton may seasonally reach limiting levels in temperate shelf waters and that oxic margins persistently supply Fe dominated by colloidal and particulate fractions to the ocean.