Desenvolvimento de metodologia de extração e pré-concentração utilizando sistema microemulsionado para determinação de Cd, Co, Cu, Ni, Pb e Tl em águas naturais e produzidas por HR-CS AAS
The determination and monitoring of metallic contaminants in water is a task that must be continuous, leading to the importance of the development, modification and optimization of analytical methodologies capab le of determining the various metal contaminants in natural environments, b...
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| Formato: | doctoralThesis |
| Idioma: | por |
| Publicado em: |
Universidade Federal do Rio Grande do Norte
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/19741 |
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| Resumo: | The determination and monitoring
of metallic contaminants in water is a task that must
be continuous, leading to the importance of
the development, modification and optimization
of analytical methodologies capab
le of determining the various
metal contaminants in natural
environments, because, in many cases, the ava
ilable instrumentation does not provide enough
sensibility for the determination of trace values
. In this study, a method of extraction and pre-
concentration using a microemulsion system with
in the Winsor II equilibrium was tested and
optimized for the determination of Co, Cd, P
b, Tl, Cu and Ni through the technique of high-
resolution atomic absorption spectrometry
using a continuum source (HR-CS AAS). The
optimization of the temperature program for
the graphite furnace (HR-CS AAS GF) was
performed through the pyrolysis and atomization
curves for the analytes Cd, Pb, Co and Tl
with and without the use of different chemical
modifiers. Cu and Ni we
re analyzed by flame
atomization (HR-CS F AAS) after pre-concentr
ation, having the sample introduction system
optimized for the realization of discrete sampling. Salinity and pH levels were also analyzed
as influencing factors in the efficiency
of the extraction. As final numbers, 6 g L
-1
of Na (as
NaCl) and 1% of HNO
3
(v/v) were defined. For the determination of the optimum extraction
point, a centroid-simplex statistical plan was a
pplied, having chosen as the optimum points of
extraction for all of the analytes, the follo
wing proportions: 70%
aqueous phase, 10% oil
phase and 20% co-surfactant/surfactant (C/S
= 4). After extraction, the metals were
determined and the merit figures obtained
for the proposed method were: LOD 0,09, 0,01,
0,06, 0,05, 0,6 and 1,5 μg L
-1
for Pb, Cd, Tl, Co, Cu and Ni, re
spectively. Line
ar ranges of ,1-
2,0 μg L
-1
for Pb, 0,01-2,0 μg L
-1
for Cd, 1,0 - 20 μg L
-1
for Tl, 0,1-5,0 μg L
-1
for Co, 2-200
μg L
-1
and for Cu e Ni 5-200 μg L
-1
were obtained. The enrichment factors obtained ranged
between 6 and 19. Recovery testing
with the certified sample show
ed recovery values (n = 3,
certified values) after extraction of 105
and 101, 100 and 104% for Pb, Cd, Cu and Ni
respectively. Samples of sweet waters of lake
Jiqui, saline water from Potengi river and water
produced from the oil industry (PETROBRAS) were
spiked and the recovery (n = 3) for the
analytes were between 80 and 112% confirming th
at the proposed method
can be used in the
extraction. The proposed method enabled the sepa
ration of metals from complex matrices,
and with good pre-concentration factor, consistent with the MPV (allowed limits) compared
to CONAMA Resolution No. 357/2005 which regulat
es the quality of fresh surface water,
brackish and saline water in Brazil. |
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