All samples were dried in an air oven at 60°C for about 72 hours, then cooled to ambient temperature, milled by means of a hammer mill and sieved through a mesh of 1mm diameter. The milled samples were stored in air- tight plastic containers until required for analysis. Sam- ple of 0.3 grammes of finely ground and dried cassava root samples were weighed in a dry clean digestion tube. Then, 2.5 ml of the digestion mixture (7.2 g salicylic acid in 100 ml of the selenium-sulphuric acid mixture) was added and allowed to react at room temperature for at least 2 hours. The digestion tubes were heated to 200°C in a block digester (Model 2040, Foss-Denmark), allowed to cool and 3 successive portions of 1 ml of hydrogen peroxide added, waiting at least 10 seconds between ad- ditions. The tubes were returned to the block digester and temperatures adjusted to 330°C. The digestion was com- plete when the digest became colourless or light yellow. The tubes were removed from the block digester and cooled to room temperature then the contents transferred into a 50 ml volumetric flask and made up to the mark with deionised water.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].