Técnicas espectroanalíticas aliadas à química verde visando à determinação de V e Mo com procedimentos de extração e pré-concentração
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2014-03-14Autor
Peixoto, Amanda Maria Dantas de Jesus
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The goal of this PhD thesis was to propose alternatives to improve the
analytical performance of F AAS (Flame Atomic Absorption Spectrometry) and
LIBS (Laser Induced Breakdown Spectroscopy) aiming V and Mo
determination. Some analytical procedures, in agreement with the Green
Chemistry principles of, as the cloud point extraction (CPE) and dispersive
liquid-liquid microextraction (DLLME) were evaluated in different kind of
samples (mineral water, medicines and soil). First was evaluated some
parameters concerning to the CPE and the instrumental parameters, using
factorial design in order to obtain the better conditions for the extraction of V
and Mo individually and simultaneously, as well as the minimum sample volume
necessary to introduce in the nebulizer. The limits of detection (LOD) achieved
with the CPE to extract individual V and Mo were 80 and 20 μg L-1, respectively.
When the CPE procedure was applied for simultaneous extraction, the LODs
were 80 and 70 μg L -1 to V and Mo, respectively. The developed procedure
was applied in two real samples of medicines and the recoveries obtained were
107 ± 4 % and 98 ± 2 % for V and Mo, respectively. Measurements in presence
of Fe (II) (possible interfering) in proportions higher than 1:10 (V: Fe and Mo:
Fe) were performed and the absorbance signals of V and Mo decrease
thereabout 30 and 50%, respectively. In the second work a procedure
employing dispersive liquid-liquid microextraction for the determination of V and
Mo by LIBS was developed and applied in water, medicines and soil samples.
Some factorial designs were also performed to optimize the best conditions for
DLLME procedure. After the optimization, a sample volume of 10 μL was dried
in a piece of aluminum foil and submitted to determination by LIBS. The
combination of DLLME-LIBS is quite feasible since microextraction is fast, easy
to apply, low-cost, they have the possibility of automation, generates little waste
and the small volume of the final extract is sufficient for the LIBS analysis. The
LOD achieved with the proposed method were 5 and 30 μg L-1 for V and Mo,
respectively. The procedure was applied to real samples of two medicines,
where the recoveries obtained by comparing with the standard addition method
and determination by ICP OES ranged 92-104% for V and 96% for Mo. In the
soil sample recovery was 97 ± 15% for V and Mo was below the LOQ and a
reference material NCS ZC 85005 (Beef Liver) where V was below the LOQ
and the recovery obtained for Mo was 102 ± 21%.
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