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A.S. Ribeiro et al. / Spectrochimica Acta Part B 57 (2002) 2113–2120
complexation and sorption onto activated carbon
The objective of this work was to develop an
appropriate methodology for the determination of
bismuth in metallurgical materials using the QTAW
and a FI-HG AAS system.
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4 or an
using a batch system 2 , a manual
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5
automated
flow system and, although such
methods are efficient, they are not simple and can
result in a low sample throughput.
2. Experimental
Hydride generation coupled with atomic absorp-
tion spectrometry (HG AAS) has been shown to
be an alternate technique with appropriate sensitiv-
2.1. Instrumentation
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ity for metallurgical materials 6 . Compared to
The generation and atomization of bismuthine
was accomplished in a FI-HG system with a
QTAW coupled with an atomic absorption spec-
trometer AAnalyst 300 (Perkin Elmer, Norwalk,
CT), equipped with a deuterium lamp for back-
ground correction. The operational conditions rec-
ommended by the manufacturer were used.
Integrated absorbance was used for signal evalua-
tion, obtained by continuous graphics. The bismuth
hollow cathode lamp (Perkin Elmer) was operated
at 12 mA. The 222.8-nm resonance line was used
with a slit-width of 0.2 nm. Argon (99.996%)
electrothermal atomization, HG AAS is less sus-
ceptible to interferences in the atomization stage
of the analyte, unless another hydride-forming
element is present as a matrix element. On the
other hand, severe interferences on hydride gen-
eration have been observed in the presence of
several frequently used alloying elements. Thus, a
species might be a severe interferent in one system,
and not influence the determination of the analyte
in another one. When an interference was observed
in HG AAS, masking agents, such as potassium
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iodide 7 , thiourea 1 , thiosemicarbazide 8 ,
EDTA 9 and iron 10–12 , as well as higher
acid or borohydride concentrations 3,10 , have
been successfully used.
The use of a flow injection (FI) system implies
a short reaction zone that allows the separation of
the generated hydride from the liquid fraction
before the reduction of interferent species. This
kinetic effect, coupled to the use of atomizers that
provide temperatures similar to those obtained in
the graphite furnace, can minimize interferences
˜
from White Martins (Sao Paulo, SP, Brazil) was
x
used as carrier gas for the generated hydride and
for drying the Nafion᭨ membrane in the gas-
drying unit.
Four types of filaments were evaluated for
QTAW: (A) 64633HLX (15 V, 150 W, Osram,
Munich, Germany); (B) 64655HLX (24 V, 250
W, Osram); (C) T3Halogen (20 V, 150 W, Osram
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x
˜
Sylvania, Sao Paulo, Brazil); (D) T3.15DLL (20
V, 150 W, Osram Sylvania). The temperature on
the surface of the tungsten coils was measured
using an Ultimax Infrared Thermometer an optical
pyrometer (Ircon, Niles, IL) equipped with a
Close-up VX-CL1 lens.
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x
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x
ˇ
13 . Matousek et al. 14 proposed the use of a
multiple micro-flame quartz tube atomizer
(MMQTA) as an ideal hydride atomizer, but they
were not able to reach temperatures higher than
1700 8C, considering the melting point of quartz.
A new quartz tube atomizer with a tungsten coil
(QTAW) for the determination of gaseous species
in AAS was recently developed and used for the
determination of As in water, sediment and biolog-
ical materials. A wide linear range, of approxi-
mately 5 times that using the MMQTA, was
obtained. It was probably the first application of a
flow system using a tungsten coil for the deter-
mination of arsenic following hydride generation,
and the authors described the potential of the
The metallic samples were dissolved on a hot
plate from Tecnal (Piracicaba, SP, Brazil).
2.2. Samples, reagents and solutions
All chemicals used were of analytical reagent
grade and water was de-ionized in a Milli-Q
system from Millipore (Bedford, MA) having a
resistivity of 18.2 MV cm. The nitric (Nuclear,
˜
Sao Paulo, Brazil), hydrochloric (Carlo Erba, Mil-
an, Italy) and sulfuric acids (Merck, Darmstadt,
Germany) were used for the optimization of the
parameters involved in the system studied as well
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system for other hydride-forming species 15 .