Facile procedures based on hyphenated ion-exchange chromatography (IEC) and inductively coupled plasma mass spectrometry (ICP-MS) were developed to determine conditional stability constants, speciate chromium species and investigate the reduction of Cr(VI). 1. Improvements were made to a method previously developed to determine the conditional stability constant, Kf’, and chelation number, n, using IEC-ICP-MS. This method allowed the accurate determination of the conditional stability constant of a simple system. However, the corresponding chelation number was significantly different to the expected value because the principal assumption, i.e. that the ligand was in excess, was not realized in the experimentation. Furthermore, it neglected complexes other than that formed with EDTA4-. By taking into account these factors, accurate Kf’ and n were obtained for Co-EDTA and Zn-EDTA systems. 2. A simple method was developed for chromium speciation analysis at sub-µg L-1 level in potable water by IEC-ICP-MS. Cr(VI) and Cr(III) were separated on IonPac® AG-7 guard column within 7.5 minutes using gradient elution with 0.1 M ammonium nitrate and 0.8 M nitric acid. H2 collision/reaction interface gas eliminated chlorine-based and carbon-based polyatomic interferences on Cr detection. Water samples were analyzed directly, without any pretreatment. The accuracy of the method was verified through accurate analysis of riverine water certified reference material. Limits of detection of 0.02 and 0.04 µg L-1 for Cr(VI) and Cr(III), respectively, were obtained. 3. This speciation analysis method was then used for kinetics studies of Cr(VI) reduction in acidified riverine water. Water was spiked with Cr(VI), with or without Cr(III), and evolution of each Cr species with time was monitored by speciation analysis, showing that the reduction of Cr(VI) was a pseudo first order reaction. By plotting the logarithm of the peak area ratio of the instant Cr(VI) concentration over that of the original spiking versus time, the reaction rate constant was obtained as the slope. The reduction rate increased with decreasing pH and increasing temperature. The activation energy of the reaction at pH 1.3 was calculated using an Arrhenius plot. This method offers the advantages of small sample consumption, minimal sample manipulation, and easy data interpretation. / Thesis (Ph.D, Chemistry) -- Queen's University, 2010-09-30 08:05:27.342

Anion-exchange chromatography with inductively coupled plasma - atomic emission spectrometry (ICP-AES) has been used for the speciation of chromium (Cr). Chromium speciation has attracted attention because of the different toxicity, Cr(III) is relatively non-toxic and Cr(VI) has been classified as a human carcinogen. The aim of the present study was to develop simple method for the speciation analysis of Cr (Cr(III) and Cr(VI)) in particulate matter of urban dust. A combination of 2% KOH + 3% Na2CO3 has been chosen as the optimal reagent for the extraction of chromium from particular matter. It was found that there was no conversion of Cr(VI) into Cr(III). The effect of separation parameters such as acidity of mobile phase was also studied. The detection limit for Cr(VI) was about 12 ng.ml-1 . Results for the determination of Cr(VI) were confirmed by the analysis of standard reference material (BCR CRM 545, Cr(VI) in welding dust loaded on a filter) with good agreement between certified (40,16 ± 0,60 μg.g-1 ) and found (37,83 ± 1,14 μg.g-1 ) values.

This thesis deals with instrumental and methodological developments for speciation analysis of gaseous mercury (Hg(g)), based on isotope dilution analysis (IDA). The studied species include Hg0, (CH3)2Hg, CH3HgX and HgX2 (where X symbolises a negatively charged counter ion in the form of a halide or hydroxyl ion). Gas chromatography hyphenated with inductively coupled plasma mass spectrometry (GC-ICPMS) was used for separation and detection of Hg(g) species. Permeation tubes were used for the generation of gaseous isotopically enriched Hg standards (tracers). These tracers were continuously added to the sample gas stream during sampling of Hg(g). A mobile prototype apparatus incorporating both the permeation source and a sampling unit for collection of Hg(g) was developed and used for this purpose. Hg(g) species were pre-concentrated on Tenax TA and / or Carbotrap solid adsorbents. Au-Pt was used for pre-concentration of total Hg(g), either as the primary medium, or as backup. Collected species were eluted from these media and introduced to the instrument by thermal desorption. Various degrees of species transformations, as well as losses of analyte during pre-concentration and elution, were found to occur for both Tenax TA and Carbotrap. The performance characteristics of these media were shown to be species specific, as well as matrix dependent. The development of an on-line derivatisation procedure allowed for minimised species transformations, as well as reduced adsorption and memory effects of ionic Hg(g) species within the analytical system. In conclusion, IDA provides an important tool for identification, minimisation and correction of the above mentioned analytical problems. Furthermore, it offers significant advantages with respect to quality assurance, compared to conventional techniques, both when it comes to rational development of new methodology, as well as for continuous validation of existing procedures. The developed methodology for speciation analysis of Hg(g) has been tested in various applications, including the determination of Hg(g) species concentrations in ambient air (both in and outdoor) and in the head space of sediment microcosms. Hg(g) species were formed in the sediments as a result of naturally occurring redox and methylation processes, after addition of an isotope enriched aqueous Hg(II) precursor. The methodology has also been used for assessing the risk of occupational exposure to Hg(g) species during remediation of a Hg contaminated soil and for studying Hg0(g) transport and Au-Pt pre-concentration characteristics in natural gases. Hg0 was used as the model species in the latter experiments, since it is believed to be the dominating form of Hg(g) in natural gas. The results indicate that the occurrence of H2S can cause temperature dependent adsorption and memory effects of Hg0(g) in the presence of stainless steel, thereby providing a plausible explanation to the variability of results for sour gases occasionally observed in the field. Hg0(g) has demonstrated overall high recovery during collection on Au-Pt tubes for all gases tested in this thesis. Recent (unpublished) results however indicate that there are potential species specific and matrix dependent effects associated with the Au-Pt based pre-concentration of Hg(g) in natural gases.

[pt] De acordo com a legislação federal no Brasil (CONAMA: Res. 20/86, Art. 21), a concentração total máxima de selênio permissível em efluentes de fontes poluidoras deve ser tão baixa quanto 0,05 mg L-1. Em refinarias de óleo, nas quais óleo cru proveniente de xisto marinho selenífero é processado, os efluentes podem conter concentrações muito mais altas, exigindo a remoção deste elemento por processos de coagulação/precipitação. O comportamento de selênio nestes processos depende, criticamente, de sua forma química; selenocianato não é eficientemente removido por tratamentos convencionais de precipitação com uso de Fe(OH)3. O conhecimento sobre especiação de selênio no rejeito hídrico é portanto importante para o desenvolvimento de adequadas estratégias de tratamento. Neste trabalho, um novo método para análise de especiação de selenito (Se-IV), selenato (Se-VI) e selenocianato (SeCN-) é descrito, e são apresentados os primeiros resultados sobre a distribuição destas espécies em rejeitos hídricos oriundos de uma planta de refino de óleo brasileira. O método é baseado em separação das espécies por cromatografia de íons seguida por detecção em linha de 77Se, 78Se e 82Se usando ICPMS. O sistema cromatográfico empregado consiste de uma bomba HPLC equipada com válvula injetora manual e uma coluna de troca aniônica (Metrosep A Supp1); esta última interfaceada com o detector (ICPMS) utilizando nebulizador concêntrico-câmara ciclônica como sistema de introdução de amostra. Detecção condutimétrica e amperométrica das espécies de selênio foram também avaliadas, usando-se um cromatógrafo comercial de íons. Vários eluentes, já descritos na literatura para análise de especiação de selênio inorgânico, foram testados (carbonato/bicarbonato, tampão ftalato, ácido p-hidroxibenzóico, etc.) e permitiram, na maioria dos casos, uma boa separação entre Se(IV) e Se(VI), no entanto, resultaram todos em tempos de retenção muito longos e como conseqüência, alargamento do pico para o íon SeCN-1. Esta desvantagem foi eficientemente eliminada usando-se uma solução de ácido cianúrico (0,003 mol L-1), modificado com acetonitrila (2% v/v) e perclorato (0,002 mol/L) como fase móvel. Típicos tempos de retenção (s) para os três analitos aqui estudados foram: selenito (210), < selenato (250) e selenocianato (450). Repetitividades em posição de picos foram melhores que 1%, e na avaliação de área de pico melhores que 3 %. Limites de detecção (em ng) para as espécies usando o instrumento ELAN 5000 e uma alça de amostragem de 500-uL foram 0,04, 0,05 e 0,09, respectivamente. Não se dispunha de materiais de referência certificados para este estudo, contudo, resultados em efluentes de complexa composição e fortificados com os íons de interesse, mostraram aceitáveis recuperações (85% - 115%) e repetitividades (RSD < 5%), validando este método para o propósito previsto. Uma vez otimizado, o método foi aplicado a efluentes hídricos de uma refinaria de óleo. Em todas as amostras analisadas, selenocianato foi de longe a espécie mais abundante, atingindo concentrações de até 90 ug L-1, seguida por selenito. As concentrações de selenato estavam abaixo do limite de detecção em todas as amostras, explicável pelas características redutoras destas águas. As concentrações totais de selênio em todas as amostras, avaliadas por geração de hidretos (HG-ICPMS) e, alternativamente, por ICPOES, excederam aquelas obtidas pela análise de especiação, indicando a presença de outras espécies de selênio, não observadas pela metodologia aqui usada. Trabalhos estão em progresso para identificar e quantificar estas espécies. / [en] According to federal laws in Brazil (CONAMA: Res. 20/86, Art. 21), the maximum permissible total concentration of selenium in effluents from polluting sources must be as low as 0,05 mg L-1. In oil refineries, in which crude oil from seleniferous marine shales are processed, wastewater may contain much higher concentrations, thus requiring removal of this element by coprecipitation/ coagulation procedures. The behavior of selenium in such processes depends critically on its chemical form; e.g. selenocyanate is not efficiently removed by the conventional treatment using Fe(OH)3 precipitation. Knowledge on the speciation of selenium in wastewater is therefore important for the development of adequate treatment strategies. In this work, a new method for the speciation analysis of selenite (Se-IV), selenate (Se-VI) e selenocyanate (SeCN-) is described and first results are presented on the distribution of these species in wastewater samples from a Brazilian oil refinery plant. The method is based on their ion chromatographic separation followed by on-line detection of 77Se, 78Se and 82Se using ICPMS. The chromatographic system employed consisted of HPLC pump equipped with a manual syringe loading injector, and an anion exchange column (Metrosep A Supp1, Metrohm); the latter interfaced with the ICPMS detector via a concentric nebulizer/cyclonic spray chamber sample introduction device. Suppressed conductivity detection and constant potential amperometric detection of these selenium species were also evaluated using a commercial IC-system. Several eluants, already described in the literature for the speciation analysis of inorganic selenium, were tested (e.g. carbonatehidrogencarbonate and phthalate buffer, p-hydroxy benzoic acid, etc) permitting in most cases a good separation of Se(IV) and Se(VI), however resulting all in very long residence times (>20min) and associated peak broadening for the polarizable SeCN - ion. This drawback could be effectively avoided using a solution of cyanuric acid (0.003 mol L-1), modified with acetonitrile (2% v/v) and perclorate (0.002 mol L-1), as the mobile phase. Typical residence times for the three analyte species here studied were: selenite (210 s) < selenate (250 s) < selenocyanate (450 s), with repeatabilities in peak position better than 1% and peak area evaluation better than 3 %. Limits of detection (in ng) for these species using an ELAN 5000 instrument and a 500-uL sample injection loop are 0.04, 0.05 and 0.09, respectively. No certified reference materials were available for this study, however, results on spiked effluent samples of complex composition showed acceptable recoveries (85% - 115%) and repeatibilities (RSD < 5 %), thus validating this method for its intended purpose. Once optimized, the method was applied to wastewater samples from a Brazilian oil refinery plant. In all samples so far analyzed, selenocyanate was by far the most abundant selenium species reaching concentrations of up to 90 uL-1, followed by selenite. Selenate concentrations were below the quantification limit in all samples, explainable by the reducing character of these waters. Total concentrations of selenium in most samples, assessed by hydride generation ICPMS and alternatively by ICPOES, exceeded those obtained from speciation analysis, indicating the presence of other selenium species, not observed by the here used methodology. Work is in progress to identify and quantify these species.

Diffusive gradient in thin film technique (DGT) represents a relatively new approach for in situ determinations of labile metal-species in aquatic systems. The DGT device passively accumulates labile species from the solution while deployed in situ, and therefore contamination problems associated with conventional collection and filtration procedures are eliminated. This study deals with a possible modification of DGT technique. The key of using DGT technique for speciation analysis of metals is to find out suitable binding phase and diffusion layer. The new resin gel based on Spheron Oxin (5 sulphophenyl-azo-8-hydroxyquinoline) ion exchanger with a higher selectivity to trace metals than Chelex 100 could potentially provide more information on metals speciation in aquatic systems. The performance of this new binding phase was tested for the determination of Cd, Cu, Ni, Pb and U under laboratory conditions. The hydrogel layer based on poly(2-hydroxyethyl methacrylate) was synthesized and tested as a new diffusion gel for application in DGT technique.

The presented thesis deals with optimization of parameters speciation analysis based on a selective hydride generation in a direct transfer mode of hydrides and on-line atomization in an atomic absorption spectrometer. In the first part of the thesis processes during generation were investigated. Important indicator of a reactions taking place in a generator is volume of hydrogen (created by decomposition of NaBH4) which is subsequently introduced to the atomizer. In this part of the thesis a new approach to determine a flow rate of hydrogen delivered to the atomizator was developed. An influence of relevant paremeters of the atomizers and atomic absorption spectrometers on basic analytical characteristics of arsenic determination based on hydride generation was performed in the second part. Three atomic absorption spectrometers were used and three sources of radiation were compared. The most important analytic characteristic was the limit of detection which is influenced by standard deviation of measurement values of blank samples and by sensitivity. The best values of the limit of detection were achieved with electrodeless discharge lamps. Key words: hydride generation, arsenic, speciation analysis, atomic absorption spectrometry

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...

The general aim of this work was a development of methodology and instrumentation for speciation analysis based on the combination of the selective generation of substituted hydrides with atomic absorption or atomic fluorescence spectrometry detection. The first topic of this work was the development of methodology and instrumentation for arsenic speciation analysis based on selective generation of substituted arsines with trapping in the cryogenic trap (U-tube packed with chromosorb) with AAS detection (HG- CT-AAS). The conditions of the selective hydride generation approach as well as working procedure of the cryogenic trap were optimized (appropriate approach for hydride generation, set up of heating program of cryogenic trap, new dryer - cartidge with NaOH, elimination of unspecific absorption, decreasing of the detection limits). The second important part of the work lay in applying of the developed method for arsenic speciation analysis in a homogenized mouse liver tissue. The direct slurry sampling to hydride generator was develop. Moreover the information about oxidation state (iAsIII,V , MAsIII,V a DMAsIII,V ) was obtain. The effect of relevant experimental parameters such as tetrahydroborate concentration, TRIS buffer concentration and time of pre-reduction of the samples by L-cysteine...

The aim of this diploma thesis was to verify the usability of the chemical generation of mercury cold vapor for speciation analysis of selected mercury compounds using high - performance liquid chromatography coupled within atomic absorption spectrometry in the determination of mercury in real tap water samples. In this work, mercuric chloride, methylmercury, ethylmercury and phenylmercury were selected as model analytes. In the first part, the working conditions of chemical generation of mercury cold vapor for each of the selected specie of mercury were optimized. Optimized equipment was used to measure the calibration dependence for each specie and the basic characteristics of the method were established. After optimization of the chemical generation, HPLC column was connected prior this derivatization step and in resulted combined apparatus HPLC - CVG - QTAAS, the separation step was optimized . At optimized conditions, the calibration dependence was measured for each specie and the basic characteristics of the developed method including HPLC separation were established. In conclusion, the proposed analytical method was tested on real flowing tap water samples. Because of low content of mercury species in these samples, the recovery of the method was established when comparing the signal of...

The aim of this work was to determine chemical species of arsenic in sea originating certified reference materials. Measurements were done using method of hydride generation. Hydrides were preconcentrated in liquid nitrogen cooled tube and detected using inductively coupled plasma mass spectrometry. During the testing of the method, mutual conversion of arsenic species was observed for inorganic arsenic, monomethyl arsenic and dimethylarsenic. Further study revealed that with presence of matrix and hydrogen peroxide, demethylation occured only in hydride generation phase, not during extraction. Dissociation of hydrogen peroxide in extracts was verified using catalase. End of the demethylation process was proved using measurement with addition of arsenic species standards. The newly invented procedure was used to determine arsenic species in reference materials with sufficient accuracy. Final results are compatible with results from different method, and already published results as well. Key words: speciation analysis, arsenic, hydride generation, seafood, inductively coupled plasma mass spectrometry