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Previous issue date: 2013-09-23 / A contamina??o de ?guas naturais por metais tornou-se assunto de interesse p?blico mundial por serem considerados biocumulativos. A determina??o e o monitoramento de contaminantes met?licos em ?guas ? uma tarefa que deve ser cont?nua e por isto a import?ncia do desenvolvimento, modifica??o e otimiza??o de metodologias anal?ticas capazes de realizar a determina??o dos v?rios contaminantes met?licos em ambientes naturais, pois em muitos casos, a instrumenta??o dispon?vel n?o apresenta sensibilidade anal?tica suficiente para a determina??o de tra?os. Neste estudo, um m?todo de extra??o e pr?-concentra??o utilizando um sistema microemulsionado, no equil?brio de Winsor II foi testado e otimizado para a determina??o dos metais Co, Cd, Pb, Tl, Cu e Ni por Espectrometria de absor??o at?mica de alta resolu??o com fonte cont?nua e atomiza??o em forno de grafite e chama (HR-CS AAS). A otimiza??o do programa de temperatura para o forno de grafite foi realizada atrav?s de curvas de pir?lise e atomiza??o para cada analito sem e com o uso de diferentes modificadores qu?micos. Cd e Pb tiveram condi??es ?timas com modificador permanente Ru, pir?lise em 700?C e atomiza??o em 1700?C, para Tl solu??o Pd/Mg foi o melhor modificador, temperaturas 600?C e 1700?C de pir?lise e atomiza??o, respectivamente e para o Co pir?lise em 800?C e atomiza??o ? 2400?C sem uso de modificador qu?mico, por?m W foi empregado como modificador permanente a fim de se prolongar o tempo de vida ?til do forno. Cu e Ni foram analisados na chama ap?s pr?-concentra??o. Avaliou-se tamb?m fatores que influenciam a efici?ncia de extra??o, atrav?s do efeito salting out. Como compromisso, 6 g L-1 de Na e 1% de HNO3 (v/v) foi definido. Para determina??o do ponto ?timo de extra??o, um planejamento centroide-simplex foi aplicado, sendo escolhido como compromisso as seguintes propor??es: 70% fase aquosa, 10% fase ?leo e 20% Cotensoativo/Tensoativo (C/T = 4). Ap?s extra??o, os metais foram determinados e as Figuras de m?rito obtidas para o m?todo proposto foi: 0,1 a 10 ?g L-1 de faixa linear, LOD 0,094, 0,011, 0,057 e 0,050 ?g L-1 para Pb, Cd, Tl e Co, respectivamente. Testes de adi??o e recupera??o na amostra certificada apresentaram valores de recupera??o ap?s extra??o de 105 e 101% para Pb e Cd, respectivamente, e nas amostras fortificadas a recupera??o para os analitos ficou entre 107 e 108% comprovando que o m?todo proposto pode ser utilizado na extra??o, possibilitou a separa??o dos metais de matrizes complexas, e ainda com bom fator de pr?-concentra??o. / 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 ?g L
-1
for Pb, Cd, Tl, Co, Cu and Ni, re
spectively. Line
ar ranges of ,1-
2,0 ?g L
-1
for Pb, 0,01-2,0 ?g L
-1
for Cd, 1,0 - 20 ?g L
-1
for Tl, 0,1-5,0 ?g L
-1
for Co, 2-200
?g L
-1
and for Cu e Ni 5-200 ?g 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.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/19741 |
| Date | 23 September 2013 |
| Creators | Costa, Emily Cintia Tossi de Ara?jo |
| Contributors | 13893734449, http://lattes.cnpq.br/0844316271215026, Huitle, Carlos Alberto Martinez, 01139059980, http://lattes.cnpq.br/2485073932883264, Maranh?o, Tatiane de Andrade, 00763832456, http://lattes.cnpq.br/2283703059305052, Ara?jo, Rennan Geovanny Oliveira, 94374597549, http://lattes.cnpq.br/3891753417538363, Leite, Ricardo Henrique de Lima, 52264343400, http://lattes.cnpq.br/3801476460958779, Dantas, Tereza Neuma de Castro, Silva, Djalma Ribeiro da |
| Publisher | Universidade Federal do Rio Grande do Norte, PROGRAMA DE P?S-GRADUA??O EM QU?MICA, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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