Measurements of heavy metal concentrations in mchicha (amaranthus) and cabbage consumed in Zanzibar by energy dispersive x-ray fluorescence spectrometry

Samples of mchicha and cabbage which are consumed in Zanzibar were analyzed for heavy metal concentration. Thirty samples of mchicha and twenty five samples of cabbage were collected from four farms and the two markets in urban west Unguja. The samples were analyzed using Energy Dispersive X-ray Fluorescence spectrometry(EDXRF) of Tanzania Atomic energy Commission (TAEC) in Arusha. The fluorescence X-ray from the samples were detected by Si(Li) detector of resolution at MnKα ≤160eV running at a rate of 50W, 50kV voltage and 1mA. The 13 elements which are Al, Cl, Cr, Mn, Fe, Ni, Zn, Cu, Ag, I, Br, Cd and Pb were detected in samples of both vegetables. The concentration of toxic elements in mchicha ranged from MDL,1-1.7µg/g, 1.66-2.55µg/g, 0.6-1.2µg/g for Cd, Ni, Cr and Pb, respectively while cabbage ranged from (MDL,1.2-2.5, 0.58-2.06, 0.7-1.3) for Cd, Ni, Cr and Pb respectively. Mchicha was found to have higher values of the essential elements Zn, Fe, Cr and Mn than cabbage. However cabbage had higher concentration of toxic elements Cd, Ni and Pb. This is probably because farmers use more chemical fertilizer in cultivating cabbage than mchicha. The mean concentration of essential elements in both types of vegetables were in the range of elemental levels reported in literature. However the concentration of toxic elements were observed to be higher than their respective maximum tolerable limit set by National and International organizations.