2. Materials and methods2.1. Instru

2. Materials and methods
2.1. Instrumentation
A Model contrAA 700 high-resolution continuum source atomic
absorption spectrometer (Analytik Jena, Jena, Germany), with a
graphite furnace and a flame atomizer in two separate sample
compartments, was used for most of the experiments. The spectrometer
is equipped with a xenon short-arc lamp operating in a hot-spot
mode, a prism pre-monochromator, an echelle grating monochromator
for high resolution, and a charge-coupled device (CCD) array
detector; the resolution is about 1.5 pm per pixel at 200 nm. An airacetylene
flame was used for the determination of Co, Cu, K, Li, Mn, Na
and Rb, and a nitrous oxide-acetylene flame for Be, Ca and Sr under
optimized conditions as specified in Table 1. High-purity acetylene and
high-purity nitrous oxide (both 99.0% v/v, White Martins, Brazil) were
used as fuel and oxidant gas, respectively. The aspiration rate used was
8 mL min−1
, and all measurements were carried out in triplicates. A
Model SFS 6 injection valve (Analytik Jena) was used to reduce the
sample consumption and to maintain the stability of the flame, as no
air is aspirated when the standard or the sample solution is changed.