Aa 140

Concentrations of Cu, As, Pb, Cr, Zn, Co, Cd and Ni were determined using sample solutions obtained from plants and soil (n = 4 for each plant and soil sample, respectively). This process was carried-out employing atomic absorption instruments (Varian AA-140 and Shimadzu AA-7000). The atomic absorption instrument was operated in the flame mode with air and acetylene. For each metal, gas flow conditions and burner height were established as recommended by the manufacturer according to the instruments’ default program. The stock solutions for performing the calibration curve were prepared from an analytical certified standard at 1000 mg/L for each metal (Merck & Co Ins. USA). To obtain calibration curves calculations were performed with 1% nitric acid. Wavelengths and detection limits used in the atomic absorption instrument are shown in Table 1:Table 1

Wavelengths and detection limit of the calibrated instrument used.

Table 1

Element	Wavelength (nm)	Detection limit (LoD)
Cd	228.8	0.500
Co	304.4	0.500
As	193.7	0.500
Zn	213.9	0.005
Pb	261.4	0.500
Ni	232.0	0.500
Cu	324.8	0.005
Cr	357.9	0.200