Determinations of levels of selected trace heavy metals in Teff sample from Minjar Shenkora Woreda, North Shewa Zone, Ethiopia

Abstract

Determination of trace heavy metals level with high accuracy and precision is one of the most important concerns of the analytical methodology as they pose health threat at high concentrations. The aim of this study was to analyze selected trace heavy metals concentration in Teff grain samples collected from Minjar Shenkora Woreda, North Shewa Zone, Amhara Regional State, Ethiopia using Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). A wet digestion procedure using mixtures of HNO3 and HCl was developed for decomposition of powdered Teff sample. The Teff grains samples were collected from the three widely Teff growing Kebeles (Namely:Ameti, Menber and Adama) of Minjar Shenkora for the analysis of eight heavy metals such as iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), Chromium (Cr), Cadmium (Cd), lead (Pb) and nickel (Ni) by using ICP-OES. The average concentration of heavy metals in White teff, Red and Mixed teff respectively were: Fe (90.547, 208.363, 104.147 ), Mn (30.631, 65.410, 28.023), Zn (13.959, 27.993, 13.062), Cu (12.304, 5.413, 2.011), Cr (5.025, 4.801, 5.527), Cd (0.012, 0.004, 0.008 ), Pb (< 0.004,< 0.004, < 0.004) and Ni (1.207, < 0.002 , < 0.002 ) mg/L. The order of uptake of heavy metals concentration by three types of teff grains were Fe > Mn > Zn > Cu > C r > Cd > Pb > Ni. In addition, the mean concentrations of heavy metals in teff samples obtained from the three kebeles farmland decreases in the following order: Fe > Zn > Mn > Cu > Cr > Co > Ni > Pb > Cd. The author concluded that the levels of heavy metals determined in the analyzed teff samples were found below the permissible limits set by FAO/WHO. Hence they are safe for human consumption at the present concentrations in all the three Teff varieties. A statistical analysis of variance (ANOVA) using excel and SPSS software revealed that there is a significant difference between the mineral content of the three teff types at 95% ( p < 0.05) CL.