Determination of essential and potentially toxic trace elements in natural and processed coconut water by microwave induced plasma optical emission spectrometry, and risk assessment

The levels of ten elements, including essential (Ca, Cu, Fe, Mg, Mn, P, and Zn) and potentially toxic trace elements (Al, B, and Ni) in coconut water were determined by microwave induced plasma optical emission spectrometry (MIP OES). The samples included natural green, mature, and industrially processed coconut water, which were all treated by acid decomposition assisted by microwave radiation. The concentrations were in the range (mg kg−1) of < 0.02–0.5 for Al, < 0.3–2.5 for B, 52.1–3853 for Ca, 0.02–0.8 for Cu, 0.1–0.508 for Fe, 13–296 for Mg, 0.03–33 for Mn, < 0.005–3.5 for Ni, 24–349 for P, and < 0.046–0.8 for Zn. Processed coconut water presented lower concentrations of essential elements than the natural drink, whereas higher Al concentrations were found in the industrially processed samples. Natural green and processed coconut water showed to be an excellent source of Mn for humans, as the ingestion of one cup of natural coconut water per day can contribute to more than 100% of the recommended daily ingestion of this element. The consumption of natural mature coconut water is not recommended, considering the high Ni levels determined in these beverages.