Desenvolvimento de fases monolíticas para métodos de extração aplicados a análise LC-UV de herbicidas em amostras de água
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2018-06-08
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Universidade Federal de Goiás
Resumo
Monolithic polymers can be defined as continuous porous polymers,
synthesized in situ in a mold. These materials have been used in chromatographic
applications due to the combination of high surface area with excellent permeability
and mass transport properties.
In this work, monolithic polymers based on styrene and divinylbenzene were
synthesized by thermal initiation via bulk polymerization in the presence of different
diluents; and via high internal phase emulsion polymerization in presence and
absence of toluene as diluent.
The monoliths produced via bulk polymerization, which were synthesized in
the presence of binary mixtures tetrahydrofuran/decanol and toluene/decanol as
polymerization diluents in the ratio 15:85 (v/v) showed mechanical resistance to be
applied as extractive phases. Both formulations produced polymers with
macroporous characteristics and the tetrahydrofuran/decanol mixture presented
larger channels, resulting in higher permeability, in this way it was used as extraction
phase for the technique of preparation of samples based on a device of sorptive
extraction of micropipette tip (DPX) applied to the determination of triazines in water
samples. Under optimized conditions the absolute recovery for the triazines varied
from 28 to 64%.
The monoliths produced by high internal phase emulsion polymerization
showed macroporosity. We have found that the effect of the solvent is more
significant for the increase in surface area and the volume and mean diameter of
pores than the effect of the reduction of these by the increase in velocity. With this,
the monolith prepared in the presence of toluene at a speed of 3000 rpm obtained a
larger surface area and a larger volume and pore diameter, resulting in a higher
permeability. The surface of this monolith was modified with polypyrrole, to verify this
film on the selectivity of the resulting phase. When submitted to the extraction
process using solid phase extraction devices (SPE), the monolith covered with PPY
films presented better extraction efficiency and its parameters were optimized for
determination of triazines in water samples by the SPE/LC-UV method (SPE/high
performance liquid chromatography with UV-vis detection). According to the figures
of merit evaluated, the proposed SPE/LC-UV method presented linearity in the
concentration range of 0.5-50 ng.mL-1
and absolute recovery of 75 to 105%, with
precision demonstrated by the coefficient of variation lower than 15%. The limit of
quantification of the method was 0.5 ng.mL-1
for all the analytes.
Thus, it was possible to develop new low-cost monolithic phases with chemical
and mechanical resistance and physicochemical characteristics suitable for use as
extractive phase in the miniaturized technique of preparation of DPX samples, as
well as SPE. The developed phases were evaluated for the determination of triazines
in water samples with adequate selectivity and sensitivity. Based on the results, the
developed phases present themselves as promising alternative to the commercial
extractive phases.
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Citação
SOARES, F. Q. Desenvolvimento de fases monolíticas para métodos de extração aplicados a análise LC-UV de herbicidas em amostras de água. 2018.125 f. Tese (Doutorado em Química) - Universidade Federal de Goiás, Goiânia, 2018.