An Optima 3000 ICP-AES instrument was modified and the equipment necessary to carry out axial excitation atomic fluorescence was designed and constructed. Using this calibrated system, preliminary fluorescence experiments were not successful. As fluorescence is proportional to source intensity, it was considered that the excitation source, a hollow cathode lamp, may not have been sufficiently intense to produce fluorescence. A novel excitation source-driver system was designed and built in-house to operate HCLs, BDHCLs and LEDs with variable modulation frequencies and duty cycle capabilities. Studies investigating lamp response to changes in modulation frequency and duty cycle indicated that a lamp operated with a lower modulation frequency range (167 - 542 Hz) and higher duty cycles (30 - 50 %) should provide the preferred intense excitation conditions for the production of fluorescence in the ICP, When a Thermo Elemental PQ2 instrument was used, fluorescence was obtained immediately. Um'variate searches were used to optimise several plasma parameters, i.e. forward power; viewing height ALC; plasma, nebuliser and auxiliary gas flow rates. Once the optimum conditions had been determined, calibration curves were plotted for each of the elements studied (Ba, Li, Mg and Na). The calibration showed excellent linearity over five orders of magnitude (R? values ranged from 0.99995 to 1.0000) and the precision on each data point was better than 5 % RSD. Limits of detection were determined to be 27.6, 0.51, 0.43 and 0.20 ug 1* for Ba, L i , Mg and Na, respectively, which approached those reported in the literature for a commercial system. Vertical profiles of the plasma, using radial excitation, were obtained for Ba, Li , Mg and Na. Using the optimum conditions for Li and Na, vertical profiles of the plasma, using axial excitation with the more intense LEDs, were obtained. Both profiles showed that there was a relatively sharp optimum, with respect to fluorescence signal, as a function of viewing height ALC. The optimum viewing heights ALC obtained, for both radial and axial excitation fluorescence, were identical, suggesting that, irrespective of the excitation arrangement employed, only particular conditions produced in the plasma give the optimum conditions for fluorescence and that these are spatially dependent. Plasma diagnostics were performed in an attempt to explain why fluorescence was observed using the plasma produced by the Thermo Elemental but not by the Optima 3000 generator. At a viewing height of 50 mm ALC, Texc and Trot were 3080 and 2500 K for plasmas produced using the Thermo Elemental generator and 3600 and 2830 K for the Optima 3000 generator, respectively. Temperatures were calculated using the mean emission intensity at particular wavelengths. The intensities of the emitting species from the Thermo Elemental ICP were lower than those obtained from the Optima 3000 ICP for supposedly 'identical' conditions. If the number of excited species gives rise to lower emission intensities, then there must be more atoms in the lower/ground state from the plasma produced using the Thermo Elemental generator. This is of vital importance because for fluorescence to occur the fluorescence emission intensity will be dependent on the number available in the ground state for excitation {i.e. a relatively 'cool' plasma is required for fluorescence to occur). As very similar plasma operating conditions and the same concentration solutions were used in the fluorescence experiments performed using both the Optima 3000 and the Thermo Elemental ICPs, the differences observed in plasma performance may be attributed to efficiency of coupling of the generators used.

Water is the essential part of every organism and it is also a vital constituent of healthy living and diet. Unfortunately water contamination over the past decade has increased dramatically leading to various diseases. As technology advances, we are detecting many pollutants at smaller levels of concentrations. Arsenic (As) is one of those major pollutants, and Arsenic poisoning is a condition caused due to excess levels of arsenic in the body. The main basis for Arsenic poisoning is from ground water which naturally contains high concentrations of arsenic. A case study from 2007 states that over 137 million people in 70 countries were affected by arsenic poisoning from drinking water [1]. This thesis work is motivated by this study and investigates the fabrication, characterization, and testing of Opuntia ficus-indica mucilage nanofiber membranes formed using a mucilage, polystyrene (PS) and iron oxide (Fe2O3) solution by an electrospinning process. Cactus mucilage is a jelly-like substance, which is extracted from the cactus pad, and is an inexpensive, biodegradable and biocompatible material. It is also an abundant material available in nature. Polystyrene is a synthetic aromatic polymer prepared from monomer styrene. Polystyrene is further dissolved using D-Limonene as a solvent. D-Limonene is a non-toxic solvent and is a citrus extract of orange peelings. In an effort to enhance adsorption capacity for the mucilage nanofiber membranes, iron oxide nanopowder is incorporated into the polymeric solution. A mucilage and polystyrene-iron oxide solution is mixed in different ratios and electrospun to obtain nanofibers. The fibers will be characterized by certain techniques such as Scanning electron microscopy (SEM), contact angle measurements, viscosity and Fourier transform infrared spectroscopy (FTIR). The fibers obtained from mucilage and PS-Fe2O3 will be further tested under Atomic fluorescence spectrometry (AFS) for testing the removal of arsenic from water. Also, a life cycle analysis (LCA) is conducted to evaluate the environmental impacts of the fabrication of the membranes by using SimaPro® software.

Speciation analysis of arsenic based on selective hydride generation and detection by atomic fluorescence spectrometry have been studied in this work. It was found that under optimum conditions of atomization in the flame in gas shield atomizer, sensitivity was approximately twice higher and detection limit was about four times lower compared to miniature diffusion flame, which is a standard atomizer for atomic fluorescence spectrometry. The conditions to generate hydrides from both inorganic forms of the arsenic, i.e. from arsenite and arsenate, with the same efficiency have been found in the batch arrangement, by using 1 mol dm-3 hydrochlorid acid and 1% solution of tetrahydridoborate. To determine only trivalent form, TRIS buffer at pH 6.00 was used together with 1% sodium tetrahydridoborate. The detection limits found for inorganic arsenic, i.e. for arsenite and arsenate, respectively, were 15 ng dm-3 and 9 ng dm-3 . It was found that in the batch arrangement under these conditions it is possible to generate corresponding hydrides methylarsonate and dimethylarsonate with the same efficiency as from the inorganic form. Finally, it was found when slightly changing the gas-liquid separator design in order to introduce the mixture of tetrahydridoborate with hydrochloric acid to the bottom of the...

(EN) The presented dissertation is devoted to hydride generation from arsenic species and its application for speciation analysis based on atomic fluorescence detection. Hydride generation from toxicologically relevant arsenic species was optimized in order to achieve a 100% efficiency. The resulted experimental setup was subsequently used for speciation analysis of arsenic in human urine by high performance liquid chromatography with detection by atomic fluorescence spectrometry. The accuracy of the developed method was verified by comparative analyses of human urine samples collected from five individuals with an independent reference method. The cleavage of As-C bond during the reaction of methylated arsenic species with tetrahydridoborate(1-) (THB) in acidic media was studied in detail. Pronounced demethylation of methylated arsenic species was found during the reaction of THB with HCl, H2SO4, and HClO4 while hydride generation from CH3COOH or TRIS buffer after prereduction with L- cysteine resulted in the exclusive formation of the corresponding hydrides. Firstly, this phenomenon can endanger the accuracy of arsenic speciation which is based on hydride generation of substituted arsanes. Secondly, the more complex arsenic species can be converted to the hydride. That was demonstrated on hydride...

The inductively coupled plasma mass spectrometer (ICP-MS) is the instrument of choice for trace and ultra-trace elemental analysis. However, the ICP-MS suffers from matrix effects. Matrix effects occur when instrument response varies as the composition of the sample matrix is changed. Matrix effects, or non-spectroscopic interferences, limit the accuracy of routine analysis. Identification of the sources of matrix effects provide a basis for reducing or eliminating them. As inaccuracies in the ICP-MS are more severe than those in the ICP atomic emission spectrometer, the problem may be due, at least in part, to the vacuum interface used to couple the plasma source and mass spectrometer. The research herein is a study of matrix effect sources in the first stage of the vacuum interface. This study utilized laser-induced fluorescence of atomic species to identify factors affecting analyte transport through the sampling orifice of the vacuum interface. Several non-idealities in the performance of the interface were found. (1) Operating conditions and sample compositions can negatively affect the efficiency with which ions are extracted through the vacuum interface coupling the plasma source to the mass spectrometer. (2) The sampling cone itself was found to suppress and narrow ion distributions in the plasma. (3) Changes in the degree of ionization were identified in the first vacuum stage. The evidence of recombination and state-changing collisions was observed in the first vacuum stage at lower power settings. Matrix effects occur in the first vacuum stage, the first step of the ion extraction process. This work shows that changes in ion transport through the first vacuum stage of the vacuum interface of an ICP-MS affect the overall performance of the instrument.

The aim of this master's thesis has been to develop and optimize the method of UV- photochemical vapor generation of cadmium volatile compounds for atomic fluorescence spectrometry. Two configurations with different materials wrapped around the low-pressure mercury vapor lamp were tested. I experimentally determined optimal conditions for both systems; the optimalized parametres included selection of photochemical reagent and its concentration, flow rate of liquids and gases, and the lenghth of the reaction coil. After finding the optimal parametres I determined the figures of merit of the method. I found from the measured data that UV-photoreactor with the quartz capillary provided lower limits of detection and thus was more suitable for generation of cadmium volatile compounds. With this arrangement and using the ferrous sulphate heptahydrate as the chemical modifier I obtained limit of detection 2,0 µg·l-1 , limit of determination 7,0 µg·l-1 , linear dynamic rate LOD-50 µg·l-1 and repeatibility 0,35 %. I also carried out the interference study in my thesis and determined the generation effeciency of cadmium volatile compounds. The interference study shows the influence of mineral acids (HCl, H2SO4, HNO3), their salts (NaNO2, NaNO3) and transition metals (Co, Ni, Cu). Based on literature review I also...

This Master thesis is a part of a project: Hydride atomizers for atomic absorption and atomic fluorescence spectrometry - new horizons (GA ČR, P206/17-04329S, principal investigator: prof. RNDr. Jiří Dědina, CSc. DSc.) of which the general target is to make a leap towards the ideal hydride atomizer by optimization of atomization based on the knowledge of the distribution of free atoms and hydrogen radicals inside the atomizers. This thesis contributes to the project by optimizing the atomization parameters for atomic absorption spectrometry with hydride generation. The atomization parameters were optimized for three different types of atomizers - multiatomizer, diffusion flame and "flame-in-gas-shield" atomizer using three different analytes - bismuth, lead and tin. Optimal atomization parameters were found for each of the atomizer and each of the analyte - carrier gas flow and flow of other gases if needed for the analysis. Calibration curves and analytical figures of merit such as sensitivity, LOD and LOQ were estimated. Final comparison is based on the data obtained from calibration curves. MDF and FIGS atomizers are mostly used with AFS detection and they provide lower sensitivity and higher detection limits with AAS detection in comparison with MMQTA. Since the analytes are known to trap...

Methods were developed for the determination of methylmercury in natural waters and sediments based on steam distillation and aqueous phase ethylation followed by gas chromatography-atomic fluorescence spectrometry. The methods were shown to be free from measurable artefactual methylation of inorganic mercury and offered improved sample throughput over existing methods. Improvements were made to existing methods for the determination of total mercury in biota, sediments and natural waters and dissolved mercury species in natural waters. These methods were applied to the study of mercury cycling in two remote field sites. The cycling of mercury species was studied in Lake Murray in Western Province, Papua New Guinea, which has been historically noted as a region of high mercury concentrations in fish. Concentrations of methylmercury and total mercury in the water column were found to be variable and consistent with non-contaminated lake systems. Concentrations of methylmercury and total mercury in the sediments were also found to be low, except for in the south of the lake, which was influenced by an intermittent supply of water and sediments with elevated mercury concentrations from the Strickland River. Methylmercury concentrations in the sediments were generally higher in the backwater areas due to littoral processes. The low concentrations of methylmercury in the sediments and waters were inconsistent with other systems previously studied in the northern hemisphere, showing a link between high mercury concentrations in fish and high concentrations of methylmercury in waters or sediments. Therefore, the biota of Lake Murray were studied in order to account for the differences between this and other systems. A study was conducted of the stable isotope ratios of carbon and nitrogen in biota from Lake Murray to elucidate key food-web interactions. This study revealed that the dominant carbon source for fish in the lake is plankton, although algae and macrophytes may also be involved in the food-web. The methylmercury bioaccumulation factors between trophic levels were similar to those measured in temperate systems of the northern hemisphere. The high concentrations of methylmercury, observed in piscivorous fish, were shown to be a consequence of the complex food-web and the number of trophic levels in the food-chains. The cycling of mercury species was studied in Lake Gordon and Lake Pedder in southwest Tasmania, which has recently been identified as being in a region of high mercury concentrations in trout and eels. The concentrations of total mercury were found to be reasonably uniform in the waters of both lakes, spatially and temporally. The concentrations of methylmercury in the waters were seasonally variable, and were consistently lower in Lake Pedder than in Lake Gordon. Dilution of methylmercury concentrations by precipitation direct to the lake surface, probably accounts for the most of the difference in methylmercury concentrations between the lakes. Owing to the long residence time of water in Lake Gordon, this reservoir mixes inputs of water with varying methylmercury concentrations. Concentrations of total mercury and methylmercury in submerged soils were low and depth profiles of mercury species in the water column did not show evidence of a gradient of mercury concentrations due to releases from the sediments. The concentrations of methylmercury observed in the water column are consistent with the concentrations observed in the fish. A budget of the mercury inputs and outputs to Lake Gordon showed that in-lake processes and sources in the catchment areas both contributed significantly to the concentrations of methylmercury in the lake. The methylation of mercury in Lake Gordon appeared to mainly occur in the surface waters (< 10 m) and was not consistent with processes leading to the methylation of mercury at the oxic/anoxic boundary observed in seepage lakes in Wisconsin. The concentrations of total mercury and methylmercury in bogs in the catchment areas of Lakes Gordon and Pedder, were high and governed by the concentration of organic matter in the sediments. The processes involved in the supply of mercury species from the Lake Gordon and Lake Pedder catchments appear to be similar to those in drainage lakes in the temperate and boreal regions of the northern hemisphere. The formation of the Lake Gordon and Lake Pedder reservoirs appears to have had little impact on the mean annual concentrations of methylmercury released to the downstream environment.

The master thesis deals with comparison of atomic fluorescence spektrometry and high resolution continuum source atomic absorption spektrometry for three methods generation of volatile compounds Antimony. In both methods of atomic antimony detection, it compares the most common chemical generation of volatile compounds (hydrides) with two alternative methods - electrochemical and UV - photochemical. The values of performance parameters for the determination of Sb(III) and Sb(V) were determined for all the above combinations. In the case of chemical generation, a surprisingly almost four times higher limit of detection of Sb(III) was found in connection with AFS detection than AAS detection. The final part was devoted to UV - photochemical vapor generation, with AAS detection for Sb(III) reaching limit of detection 4,96 ppb, for Sb(V) 8,63 ppb. Although UV - photochemical generation of volatile antimony compounds did not reach such performance parameters as chemical or electrochemical generation, it was observed that the sensitivity of antimony determination increased greatly when introducing oxygen into the apparatus. The interference study also found a significant positive effect of Fe(II) on the generation efficiency, and this modification partially persisted without further introduction of these...

[pt] O objetivo do trabalho foi desenvolver métodos analíticos capazes de especiar mercúrio, determinando metilmercúrio (CH3Hg), etilmercúrio (CH3CH2Hg), mercúrio inorgânico (Hg2+, Hg0), em água de produção (AP), e tiomersal (C9H9HgNaO2S), em urina e em efluente de uma indústria farmacêutica. Apesar de existir muitos métodos para quantificar espécies de mercúrio, poucos estudos abordam a especiação em AP, amostras conhecidas por ter altos teores de óleo e sal. Além disso, o uso de nanomateriais, como pontos quânticos de grafeno (GQDs), sozinho ou dopados de nanopartículas de dióxido de titânio (GQDs-TiO2 NPs), foram usados como agentes fotocatalíticos para produzir o mercúrio elementar detectado. As técnicas analíticas utilizadas para a detecção de mercúrio total e para especiação por mercúrio foram espectrometria de absorção atômica com vapor frio em cela multipasso (multipath-CV-AAS) e espectrometria de fluorescência atômica com vapor frio acoplado ao sistema de cromatografia gasosa (GC-CV-AFS). No primeiro trabalho, a foto-degradação do tiomerosal foi alcançada utilizando luz visível e GQDs, obtidos a partir da hidroexfoliação de ácido cítrico e glutationa, como foto-catalisador. O Hg0 gerado (usando condições experimentais ajustadas) foi detectado por multipath-CV-AAS, permitindo a quantificação de tiomersal em concentrações equivalentes a 20 ng L-1, mesmo em amostras complexas como efluentes aquosos da indústria farmacêutica e em urina. A cinética de reação (pseudo-primeira ordem com k = 0,11 min-1) foi determinada. O segundo trabalho relata o método de especiação de mercúrio em AP usando o sistema CV-AAS. Sob condições ajustadas de concentrações de sal e óleo (por diluição e centrifugação), uma alíquota de amostra foi tratada com SnCl2, levando ao Hg0 quantificado como mercúrio inorgânico original. Uma segunda alíquota de amostra foi exposta a UV (sob condições otimizadas) que promoveu a oxidação de CH3Hg a Hg2+, formando Hg2+ que foi posteriormente reduzido, com SnCl2, produzindo o Hg0 referente ao teor total de mercúrio na amostra. O teor de CH3Hg foi obtido pela diferença nos resultados alcançados para as duas alíquotas. O efeito matriz imposto por óleo e sal foram estudados e, apesar de afetar a intensidade do perfil do tempo de mercúrio, a quantificação foi alcançada com sucesso com padrões ajustados (assemelhamento de matriz) combinando quantidades de NaCl e óleo mineral. As medições de condutividade (estimativa de teor de sal) e turbidimétrica (estimativa de teor de óleo) foram feitas para as amostras de PW, a fim de permitir o ajuste adequado da amostra aos padrões correspondentes (contendo óleo mineral a 5 mg L-1 e NaCl a 5 g L-1). O método de adição de analito também foi utilizada e o limite de quantificação foi de 12 ng L-1. / [en] The aim of the present work was to develop analytical methods capable of determining mercury species such as methylmercury (CH3Hg), ethylmercury (CH3CH2Hg), inorganic mercury (Hg2+, Hg0), in produced water (PW) and urine, as well as thiomersal C9H9HgNaO2S) in effluent from a pharmaceutical industry and in urine. Despite many methods for quantifying mercury species are reported, few studies address speciation in PW, sample known to have high oil and salt contents. Besides, the use of nanomaterials such as graphene quantum dots (GQDs) alone or decorating titanium dioxide nanoparticles (GQDs-TiO2 NPs) were used as photocatalytic agents to produce the detected elemental mercury. The analytical techniques used for total mercury detection and mercury speciation were multipath cold vapor atomic absorption spectrometry (multipath˗CV˗AAS) and gas chromatography cold vapor atomic fluorescence spectrometry (GC˗CV˗AFS). In the first work, the photo-degradation of thiomersal has been achieved using visible light and GQDs, obtained from hydro-exfoliation of citric acid and glutathione, as catalysts. The generated Hg0 (using adjusted experimental conditions) was detected by multipath-CV-AAS, enabling quantification of thiomersal at values as low as 20 ng L-1 even in complex samples as aqueous effluents from the pharmaceutical industry and in the urine. The reaction kinetic (pseudo-first-order with k = 0.11 min-1 ) was determined. The second work provided a speciation method for mercury in PW using multipath-CV-AAS. Under adjusted salt and oil contents (by dilution and centrifuging), a sample aliquot was treated with SnCl2, leading to the Hg0 quantified as the original inorganic mercury. A second sample aliquot was exposed to UV (under optimized conditions) that promoted oxidation of CH3Hg to Hg2+, which was then reduced, with SnCl2, producing the Hg0 relative to the total mercury content in the sample. The CH3Hg content was obtained by the difference in results achieved for both aliquots. Matrix effects imposed by oil and salt were studied, and although affecting the intensity of the mercury time profile, quantification was successfully achieved by matrix-matched standards containing NaCl and mineral oil.