Título: | NEW ANALYTICAL APPROACHES FOR SPECTROFLUORIMETRIC DETERMINATION OF CYCLOFENIL AFTER PHOTOCHEMISTRY DERIVATION AND FOR STROBILURIN VOLTAMMETRIC DETERMINATION USING MERCURY ELECTRODE AND CU (II) VOLTAMMETRIC DETERMINATION USING BISMUTH FILM ELECTRODE | ||||||||||||||||||||||||||||||||||||||||||||
Autor: |
WAGNER FELIPPE PACHECO |
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Colaborador(es): |
RICARDO QUEIROZ AUCELIO - Orientador PERCIO AUGUSTO MARDINI FARIAS - Coorientador |
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Catalogação: | 17/FEV/2009 | 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=13052&idi=1 [en] https://www.maxwell.vrac.puc-rio.br/projetosEspeciais/ETDs/consultas/conteudo.php?strSecao=resultado&nrSeq=13052&idi=2 |
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DOI: | https://doi.org/10.17771/PUCRio.acad.13052 | ||||||||||||||||||||||||||||||||||||||||||||
Resumo: | |||||||||||||||||||||||||||||||||||||||||||||
In this work, analytical approaches for the selective determinations of
cyclofenil, stroblilurins (azoxystrobin and dimoxystrobin) and Cu (II) have been
developed. The determination of cyclofenil was made by taking advantage of their
fluorescent photoderivative. In order to achieve maximum fluorescence (250/410),
the best conditions for derivatization and for the analytical measurements have
been optimized firstly by univariate approach and then by a multivariate way
(central composite design). The optima conditions were: 2 h of UV exposition
time and solvent system composed by methanol/Britton-Robinson buffer pH 10.5.
A mechanism for this photochemical reaction has been proposed, with the
indication of the structure of two most probable photoderivades. In such
conditions, the analytical response presented a linear and homocedastic behavior
(r2=0,9951) up to 8 x 10-5 mol L-1. Limit of detection (LQ) and limite of
quantification (LQ) for the spectrofluorimetric determination were respectively
1.1 x 10-8 mol L-1 and 3.,7 x 10-7 mol L-1. The methodology was proven to be
adequate to quantify cyclofenil in pharmaceutical formulations with mean
recovery of 98.3 + 3.9%. For the determination of cyclofenil in urine, it was
necessary the use of a separation technique (HPLC). In such case, the fluorescent
signal from one of its photochemical derivatives (7.0 min retention time) was
chosen. Efficient separation from the matrix background was achieved using a C-
18 column, gradient elution using methanol/water system. The use of an internal
standard (m-toluil acetate) allowed recoveries of 99.5 + 3.4 % for cyclofenil
fortified urine samples. In the case of the selective anodic stripping voltammetric
determination of Cu (II) using bismuth film electrode, the overlapping between
Cu (II) and Bi (III) needed to be eliminated, since both species present redissolution
peaks near +80 mV. The interference was solved by the addition of
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hydrogen peroxide in the working cell which caused the shifting of Cu (II) redissolution
peak to +200 mV, probably caused by the deposition of oxidated
copper species on the electrode surface. The experimental and instrumental
conditions have been optimized in an univariated way in order to achieve a
maximum analytical signal for Cu (II). As a result, the optimized conditions were:
-1400 mV of deposition potential, 400 mV s-1 scan rate, 100 mV amplitude. In
such conditions, a linear and homoscedastic behavior (r2 = 0,9927) analytical
response was found. The method has been applied for sugarcane spirit samples
where values of 2.9 x 10-7 mol L-1 and 9.5 x 10-7 mol L-1 were achieved
respectively for LD and LQ. The results from such determinations had been
compared with the ones from another technique (graphite furnace atomic
absorption spectrometry) with statistically similar results. The simultaneous
determination of Cd (II) and Pb (II) was also achieved using a compromised
condition. For the strobilurins, a sensible and selective voltammetric method was
developed to be applied in foods, river water and industrial juices. The
experimental conditions have been developed in order to achieve a maximum
analytical signal for the simultaneous determination of azoxistrobin and
dimoxistrobin in the hanging mercury drop electrode. The optimized conditions
were: deposition potential at -300 mV, 150 mV amplitude, 300 mVs-1 using the
square wave mode. In such conditions, the azoxystrobin and the dimoxystrobin
peaks were found at – 928 mV and -650 mV respectively. Linear analytical
response (r2>0,99) and homoscedastic behavior have been observed. LD and LQ
where respectively 3.6 x 10-7 mol L-1 and 1,2 x 10-6 mol L-1 for azoxystrobin and
7.1 x 10-7 mol l-1 and 2.4 x 10 -6 mol L-1 for dimoxystrobin. Enough selectivity
was achieved in complex samples and no interferences from others strobilurins
(piraxystrobin and picoxystrobin) was found. A simple mechanism for the redox
process at the mercury electrode was proposed.
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