The digested samples were analyzed for trace metals (iron and zinc), using the Atomic Ab- sorption Spectrophotometer, (Model AA-6300, Tokyo- Japan). The instrument was calibrated using standard solutions of iron (Fe in HNO3; iron standard solution 10 ppm) and zinc (Zn in HNO2; zinc standard solution 10 ppm) and measured by atomic absorption as they were absorbing radiations from element-specific hollow cath- ode lamps at a wavelength of 248.3 nm and 213.9 nm, respectively. The absorbencies obtained were used to calculate the concentrations of the metals in the different samples [41].