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Registros recuperados: 8
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Analytical methods for mercury speciation in several matrixes: a review IPB - Escola Superior Agrária
Ramalhosa, Elsa; Río-Segade, Susana.
Mercury is one of the hazardous contaminants that may be present in the environment. Moreover, its toxicological effects are strongly dependent on the chemical form of the element, being the organic species the most toxic. In spite of this, the determination of mercury compounds in environmental samples, such as water, soils, sediments and biological matrixes, is of great importance. This review examines the current state of the sample treatments that have been developed, during the last 18 years (1990-2007),previous to separation and detection of mercury compounds, namely acid lixiviation, distillation,alkaline digestion and supercritical fluid extraction, as well as of the chromatographic techniques (gas chromatography and high performance liquid...
Tipo: Article Palavras-chave: Mercury; Speciation; Analytical methods; Gas chromatography; Liquid chromatography.
Ano: 2008 URL: http://hdl.handle.net/10198/3605
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Effect of organic matter on determination of reactive mercury in contaminated waters IPB - Escola Superior Agrária
Ramalhosa, Elsa; Río-Segade, Susana; Pereira, Eduarda; Vale, Carlos; Duarte, Armando.
Dissolved reactive mercury was determined in water samples from Ria da Aveiro, a coastal lagoon contaminated by mercury. Concentrations increased with acid dilution to a maximum of 193% in samples containing organic matter with high aromaticity, as inferred from absorbances at 250, 280 and 365 nm. Laboratory experiments with potassium hydrogenoftalate and humic acids solutions proved the influence of aromaticity in complexing mercury, how acid dilution protonates the aromatic Hg-complexes and consequent release of labile forms of mercury to solution. On the basis of these results it is proposed that natural waters from mercury contaminated ecosystems should be analysed without dilutions, otherwise additional studies should be performed to access the...
Tipo: Article Palavras-chave: Reactive mercury; Organic matter; Flow injection; Cold vapour atomic Fluorescence Spectrometry; Natural waters.
Ano: 2003 URL: http://hdl.handle.net/10198/3954
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Mercury cycling between the water column and surface sediments in a contaminated area IPB - Escola Superior Agrária
Ramalhosa, Elsa; Río-Segade, Susana; Pereira, Eduarda; Vale, Carlos; Duarte, Armando.
Mercury cycling in the water column and upper sediments of a contaminated area, the Largo do Laranjo, Aveiro (Portugal), was evaluated after determination of reactive and non-reactive mercury concentrations in the water column and pore waters of sediments, collected in several places of this bay. In the water column, reactive mercury concentrations varied between 10 and 37 pmol dm−3, the highest values being observed near the mercury anthropogenic source. However, reactive mercury was a narrowly constrained fraction of the total mercury, making up only 4–16% of the total, showing evidence of the importance of dissolved organic matter on mercury transport. In sediments, higher concentrations of mercury were also determined near industrial discharges....
Tipo: Article Palavras-chave: Reactive mercury; Non-reactive mercury; Sediments; Pore waters; Diffusion; Largo do Laranjo.
Ano: 2006 URL: http://hdl.handle.net/10198/1123
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Mercury cycling between water column and upper sediments in a contaminated area (Largo do Laranjo, Aveiro, Portugal) IPB - Escola Superior Agrária
Ramalhosa, Elsa; Río-Segade, Susana; Pereira, Eduarda; Vale, Carlos; Armando, Duarte.
The fate and reactivity of anthropogenic mercury in aquatic environment is of major concern owing to its toxicity to most organisms and man. In Ria de Aveiro, a chloralkali plant has been discharging mercury during decades into one of the remotest branches. Most of the discharged mercury settles down in Largo do Laranjo, an inner bay of 1.5 km'. Since 80's, several works have identified high mercury concentrations in sediments, suspended particulate matter and water [I, 2, 3]. The highest concentrations of mercury (max. 35 Og g") were found in sediments at 40 cm depth, corresponding to the period of maximum industrial production [2]. However, there is an escape of particulate mercury when surface sediments are resuspended and transported by the tide to the...
Tipo: ConferenceObject Palavras-chave: Mercury; Water column; Sediments; Cycling.
Ano: 2004 URL: http://hdl.handle.net/10198/3655
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Microwave treatment of biological samples for methylmercury determination by high-performance liquid chromatografy – cold vapour - atomic fluorescence spectrometry IPB - Escola Superior Agrária
Ramalhosa, Elsa; Río-Segade, Susana; Pereira, Eduarda; Vale, Carlos; Duarte, Armando.
A simple and rapid microwave-assisted alkaline digestion procedure was developed in combination with high performance liquid chromatography-ultraviolet post-column oxidation-cold vapour atomic fluorescence spectrometric detection for methylmercury determination in biological tissues. Since the stability of methylmercury in methanolic potassium hydroxide solution under microwave irradiation was verified, the microwave-assisted extraction procedure was optimized in terms of quantitative recovery of methylmercury and minimum time required. The alkaline extracts were subjected to clean-up steps with dichloromethane and hydrochloric acid in order to reduce matrix interferences in methylmercury determination. The effects of matrix interferences were checked by...
Tipo: Article Palavras-chave: Methylmercury; Microwave treatment; Biological samples; HPLC-CV-AFS.
Ano: 2001 URL: http://hdl.handle.net/10198/3950
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Microwave-assisted extraction for methylmercury determination in sediments by high performance liquid chromatography-cold vapour-atomic fluorescence spectrometry IPB - Escola Superior Agrária
Ramalhosa, Elsa; Río-Segade, Susana; Pereira, Eduarda; Vale, Carlos; Duarte, Armando.
A simple and rapid procedure for methylmercury extraction from sediments based on microwave-assisted alkaline digestion with methanolic potassium hydroxide was optimized on parameters such as microwave power, extraction time and sample size. Organomercury species were extracted with dichloromethane in hydrochloric acid medium and back-extracted into ultra-pure water. The sediment extracts were injected into an analytical system composed of high-performance liquid chromatography-ultraviolet-post-column oxidation-cold vapour-atomic fluorescence spectrometry (HPLC-UV-PCO-CV-AFS) for methylmercury determination. Quantitative methylmercury recoveries were obtained when 0.15 g of sediment were suspended into 6 mi of 25% m/v methanolic potassium hydroxide and the...
Tipo: Article Palavras-chave: Methylmercury; Microwave-assisted extraction; HPLC-CV-AFS.
Ano: 2001 URL: http://hdl.handle.net/10198/3941
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Monomethylmercury behaviour in sediments collected from a mercury-contaminated lagoon IPB - Escola Superior Agrária
Ramalhosa, Elsa; Río-Segade, Susana; Pereira, Eduarda; Vale, Carlos; Duarte, Armando.
Surface sediments and sediment cores were collected in a mercury (Hg)- contaminated lagoon, namely Largo do Laranjo – Ria de Aveiro, Portugal and analysed in order to establish the monomethylmercury (MeHg) behaviour in this kind of environment. In surface sediments, this compound was only detected in one place (13.2 ng g-1 (dry weight)). In this site, it was determined one of the lowest redox potentials (22 mV), indicative of oxic/anoxic conditions, which favours Hg methylation by enhancing the sulphate-reducing bacteria activity. However, the MeHg percentage obtained was low, namely less than 0.1% of the total Hg. This is probably due to Hg deposition with organic matter and iron oxyhydroxides, decreasing Hg availability to methylation. At the deeper...
Tipo: Article Palavras-chave: Monomethylmercury; Total mercury; Acid volatile sulphides; Organic matter; Iron species; Portugal.
Ano: 2011 URL: http://hdl.handle.net/10198/3653
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Simple methodology for methylmercury and inorganic mercury determination by high performance liquid chromatography-cold vapour atomic fluorescence spectrometry IPB - Escola Superior Agrária
Ramalhosa, Elsa; Río-Segade, Susana; Pereira, Eduarda; Vale, Carlos; Armando, Duarte.
An analytical methodology was developed to separate and quantify methylmercury (MeHg) and inorganic mercury by high-performance liquid chromatography (HPLC)-cold vapour atomic fluorescence spectrometry (CV-AFS). The use of UV oxidation of the organic forms of mercury, the tin(II) chloride reduction in acidic medium of mercury and the introduction of a water vapour trap based on H2SO4/CaCl2 resulted in a low detection limit (DL) (10 +/- 2 pg, mean value +/- S.D.). The apparatus was operationally optimised through the modified simplex method leading to an increase of the signal by a factor of 2. The method performance has been tested by determining the MeHg concentration in a sediment certified reference material (CRM) and the results were statistically...
Tipo: Article Palavras-chave: Methylmercury; Cold vapour atomic fluorescence spectromety; Liquid chromatography; UV radiation; Simplex optimisation.
Ano: 2001 URL: http://hdl.handle.net/10198/3946
Registros recuperados: 8
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