Assessment of heavy metals in rice using atomic Absorption spectrophotometry – a study of different rice varieties in Pakistan

Accumulation heavy metals, upon accumulation in human body, are known to possess quite toxic effects. They are ubiquitously found in earth crust and tend to accumulate in crops grown in heavily contaminated soil and hence enter the food chain. This study was based on the analysis of heavy metals in eighteen selected varieties of rice (Oryza sativa L.) that circulates in local market of Karachi, Pakistan. Few heavy metals namely, Cadmium (Cd), Chromium (Cr), Cobalt (Co), Copper (Cu), Lead (Pb), Manganese (Mn), Nickel (Ni), and Zinc (Zn) were analyzed using Atomic Absorption Spectroscopy (AAS). Rice samples were digested using nitric acid (conc.). Average concentrations of Cd, Co, Cr, Pb, Ni were 7.3, 10.6, 107, 117, 139 μg kg-1 of rice respectively, whereas, the respective concentrations of Cu, Mn, and Zn were found to be 4.7, 9.7, and 14.6 mg kg-1 of rice. The results from this study when compared with previous studies revealed that the Pakistani rice is found to have relatively less concentration of these heavy metals. (author)