Determination of Cu, Mn, Hg, Pb, and Zn in the Outer Tissue Washings, Outer Tissues, and Inner Tissues of Different Vegetables Using ICP-OES
Ibrahim A. Arif, Haseeb A. Khan, Ali A. Al Homaidan, Anis Ahamed
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Environmental Analysis Unit, Prince Sultan Research Chair for Environment and Wildlife, College of Sciences,
King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
Pol. J. Environ. Stud. 2011;20(4):835–841
We have determined the levels of five heavy metals (Cu, Hg, Mn, Pb, Zn) in outer tissue washings, outer tissues, and inner tissues of different vegetable samples (beans, cabbage, capsicum, carrot, cauliflower, cucumber, eggplant, green pepper, pea, and tomato) from the Qassim region of Saudi Arabia. Instead of using the customary dried tissue power, we conducted all the analysis directly in the wet tissues following microwave digestion; the levels of heavy metals being reported in wet as well as dry tissue using the watercontent factor. Pb was absent in the washings but present in most of the vegetables in the range of 0.013- 0.251 μg/g wet tissue (0.201-5.055 μg/g dry tissue). Although traces of Hg (5.994-6.520 ng/g wet tissue) were present in the washing, this metal was not detected in the vegetable tissues. Cu was observed in the range of 0.079-1.785 μg/g wet tissue (1.104-22.919 μg/g dry tissue), whereas the range of Mn was found to be 0.239- 3.263 μg/g wet tissue (4.626-47.036 μg/g dry tissue). Only in the outer tissues of peas were Cu levels found to be slightly higher (22.919 μg/g dried tissue) than the recommended upper limit of 20 μg/g. Zn was detected only in the beans, green pepper, and peas; its concentration was much higher in outer (552.77 μg/g) and inner (686.71 μg/g) tissues of green pepper than the recommended upper limit of 100 μg/g. The lower limits of detection (LOD) and quantification (LOQ) for Hg were found to be 0.81 and 1.61 ng/kg, respectively. The LOD and LOQ for the remaining heavy metals were as follows: Cu (1.28 and 4.27 μg/kg), Mn (0.23 and 0.77 μg/kg), Pb (7.56 and 24.79 μg/kg), and Zn (5.98 and 19.96 μg/kg). Our findings suggest that the analysis of heavy metals directly in the wet samples provides a quick alternative for screening of heavy metals as this method can determine the heavy metals well below their toxic limits. The presence of heavy metals in the washings of the outer tissues of vegetables points toward the importance of thoroughly washing vegetables before consumption.