2. Experimental
2.1. Instrumentation
All measurements were carried out using in a Model contra 700
high-resolution continuum source atomic absorption spectrometer
(Analytik Jena AG, Germany), equipped with a transversely-heated
graphite tube atomiser. The contra 700 was equipped with a xenon
short-arc lamp with a nominal power of 300 W operating in a hot
spot mode. The high-resolution double monochromator had a prism
pre-monochromator, a high-resolution echelle monochromator and a
linear charge coupled device (CCD) array detector with 588 pixels,
200 of which were used for analytical purposes. The analytical lines at
283.306 nm for Pb and 359.349 nm for Cr were used. Atomic absorption
was measured using the centre pixel (CP) and the two adjacent pixels
(CP ± 1), corresponding to a spectral interval of 4.8 pm for Pb and