Título: | DEVELOPMENT OF METHOD FOR DETERMINATION OF AS, SB AND SE IN BIODIESEL AND PETROLEUM BY INDUCTIVELY COUPLED PLASMA OPTICAL EMISSION SPECTROMETRY WITH SAMPLE INTRODUCTION BY HYDRIDE GENERATION (HG ICP | ||||||||||||||||||||||||||||||||||||||||
Autor: |
FLÁVIA GALVÃO WANDEKOKEN |
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Colaborador(es): |
TATIANA DILLENBURG SAINT PIERRE - Orientador ROSELI MARTINS DE SOUZA - Coorientador |
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Catalogação: | 04/OUT/2011 | 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=18416&idi=1 [en] https://www.maxwell.vrac.puc-rio.br/projetosEspeciais/ETDs/consultas/conteudo.php?strSecao=resultado&nrSeq=18416&idi=2 |
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DOI: | https://doi.org/10.17771/PUCRio.acad.18416 | ||||||||||||||||||||||||||||||||||||||||
Resumo: | |||||||||||||||||||||||||||||||||||||||||
With the increasing world population and the consequent increasing in
industrial activities and fuel consumption, chemical pollution has been a major
problem of the XXI century. Alternatives that can minimize such problems are
targets of researches, such as the use of biodiesel, a renewable and less polluting
fuel. Elements usually found in low concentrations, such as As, Sb and Se,
become toxic to human health when in concentrations above certain limits and,
therefore, should be monitored in several samples, such as fuels. For Sb the
acceptable daily intake (ADI) is 6 mg day(-1) for each kg of body weight and, for
Se, concentrations above 50-200 mg per day are considered toxic. The As
acceptable limit in drinking water is 0.01 mg L(-1) and values above 7.5 x 10-3 g m(-3)
are associated to risk of lung cancer. These elements may be original constituents
of petroleum and its derivatives or be added as contaminants at some step of the
refining process. In the case of biodiesel, these elements can be present due to the
use of fertilizers and pesticides in the crops that produce the oil used in the
biodiesel production. These elements can be released to the atmosphere during the
fuel burning in the motor. The usually low concentrations of these elements can
be below the detection limit of some techniques, such as ICP OES with sample
introduction by standard pneumatic nebulization. In these case, the vapor
generation is an interesting alternative for sample introduction, since it provides a
significant improvement in the sensitivity of the analytical technique. This study
aimed to simultaneously determine As, Sb and Se in crude oil and biodiesel
samples, using HG-ICP OES. For that, samples had to be subjected to acid
decomposition in a block digester, thus allowing calibration with inorganic standard solutions. Different pre-reduction conditions were studied (HCl, thiourea and ascorbic acid with KI), being evaluated the reagents concentrations and heating time. The conditions using HCl and thiourea showed the best results and had their parameters multivariate optimized, as well as the parameters of the vapor
generation: sample, sodium borohydride and carrier gas flow rates. Established
the best conditions for analysis and respecting the limitations of the technique, the
method was validated by analysis of a residual fuel oil certified material (NIST
1634c), biodiesel from soybean oil (NIST 2772) and biodiesel from animal fat
(NIST 2773), using the two cited pre-reduction conditions. In this case, the use of
HCl as pre-reducer was more efficient, with recoveries between 90% and 99% for
the three analytes. Pre-reduction with thiourea was effective only for Sb, with
recovery around 104%, while the recoveries for As and Se were between 57% and
29%. Thus, HCl was employed as the pre-reducer in the proposed method. The
optimized conditions for the generation and used for the analysis of the samples
were: sample flow rate, 3.0 mL min(-1); NaBH4 flow rate, 1.5 mL min(-1); carrier gas
flow rate, 0.8 L min(-1) and concentration of HCl, 8 mol L(-1). A study to verify a
possible interference of Ni under the optimized conditions for vapor generation
revealed that this interference does not affect the determination of As, Sb and Se
when employing HCl 8 mol L(-1). Therefore, crude oil and biodiesel samples were
analyzed at the previously optimized conditions. Only As and Se were detected in
crude oil samples, while the concentrations of these analytes in the biodiesel
samples were always lower than the obtained LODs. Although, the recovery for
the Sb additions in biodiesel and crude oil samples were in a large range, between
72% and 111%, indicating that HCl is not the most efficient pre-reducer for this
element, it can be said that, for multielemental analysis whose objective is to
evaluate the presence of this element or a possible contamination by it, this prereducer
can be employed.
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