Título: | DETERMINATION OF TOTAL AS IN OCEANIC WATER BY HG AFS | ||||||||||||||||||||||||||||||||
Autor: |
CAROLINA LYRIO TENORIO-DAUSSAT |
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Colaborador(es): |
REINALDO CALIXTO DE CAMPOS - Orientador MARIANA ANTUNES VIEIRA - Coorientador |
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Catalogação: | 20/OUT/2010 | Língua(s): | PORTUGUESE - BRAZIL |
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Tipo: | TEXT | Subtipo: | THESIS | ||||||||||||||||||||||||||||||
Notas: |
[pt] Todos os dados constantes dos documentos são de inteira responsabilidade de seus autores. Os dados utilizados nas descrições dos documentos estão em conformidade com os sistemas da administração da PUC-Rio. [en] All data contained in the documents are the sole responsibility of the authors. The data used in the descriptions of the documents are in conformity with the systems of the administration of PUC-Rio. |
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Referência(s): |
[pt] https://www.maxwell.vrac.puc-rio.br/projetosEspeciais/ETDs/consultas/conteudo.php?strSecao=resultado&nrSeq=16482&idi=1 [en] https://www.maxwell.vrac.puc-rio.br/projetosEspeciais/ETDs/consultas/conteudo.php?strSecao=resultado&nrSeq=16482&idi=2 |
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DOI: | https://doi.org/10.17771/PUCRio.acad.16482 | ||||||||||||||||||||||||||||||||
Resumo: | |||||||||||||||||||||||||||||||||
The increase in industrial activity has increased human exposure to metals and
metalloids exponentially. In this context, arsenium is a good example, being
increasingly found in several natural environments. It is an element with no
essential biological function, and possessed of elevated toxicity. The discharge of
toxic elements in aquatic bodies can promote significant alterations in physical,
chemical and biological characteristics, of both the receiving body and the metal
itself, regarding its original state. In Brazil, the legislative resolution CONAMA
nº 357 of March 17th, 2005 (CONAMA, 2005) is used, which fixes the maximum
limits of contaminants in water. The determination of trace-elements in sea-water
is of great importance, due to the possibility of bioaccumulation and
bioamplification in the food chain. Thus, it is important to establish an easy and
efficient method to determine trace-elements in marine waters. The present study
aims to compare two arsenium determination techniques for ultra-trace levels:
atomic fluorescence spectrometry coupled to hydride generation and ICP-MS with
the use of a collision cell. The former has as its major advantage its own hydride
generation, that separates the analyte from the matrix, minimizing possible
interferences while the latter, due to the use of the collision cell, proposes the
determination of As even in the presence of high chloride concentrations, while
avoiding isobaric interferences. The samples used in this study were collected
from the Brazilian coast. Using HG AFS, the samples were diluted 1+1, mixed in
a solution of HCl and KCl and ascorbic acid, in order to obtain final
concentrations of 3,5 mol L-1, 1 and 0,2% (m/v), respectively. The reducing
solution responsible for the hydride generation was consisted of NaBH4 1,5%
(m/v), dissolved in NaOH 0,4% m/v. The analysis were conducted making use of
external calibrations with aqueous standards, obtaining a LOD of 36 ng L-1 (3sd),
sampling frequency of 45 h-1 and RSD of 2%, obtained from ten measurements of
a spike of 500 ng L-1 in one of the samples. When using the ICP-MS
methodology, the samples were diluted 10 times (1 + 9). In this case, the
calibration conducted was a standard addition, due to interference of the saline
matrix in the analysis. A collision cell with He gas was used, in order to minimize
saline matrix interferences. The HG AFS technique was demonstrated as the most
adequate choice for the direct determination of total As in sea water, due to its
adequate limits of detection and absence of interferences. A pre-concentration
method was not necessary, and external aqueous calibration was possible. The
method was demonstrated as precise and quick, although there was need of a prereduction
step. On the other hand, the ICP-MS with direct sampling aspiration,
even with the use of a collision cell, did not lead to the expected results while
analyzing certified reference material of sea water, while the HG AFS technique
did. An observation was made that, in conditions where isobaric interferences
were avoided, the limit of detection became improper for the analysis of the
samples in question.
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