Elemental chemical composition and As speciation in rice varieties selected for biofortification
Toxic elements, essential elements and other elements were determined in Brazilian rice by inductively coupled plasma - mass spectrometry (ICP-MS). The levels of As and Cd ranged from 34.4 to 86.5 ng g-1 and from 3.8 to 8.4 ng g-1, respectively. For Fe and Zn, the concentrations varied from 41.0 to 138.6 μg g-1 and from 18.0 to 38.4 μg g-1, respectively. A method for As speciation using hydride generation was developed. The developed method showed the lowest detection limits: 0.004 μg L-1 for dimethyl arsenic acid (DMA), 0.003 μg L-1 for monomethylarsonic acid (MMA) and arsenite (As3+), and 0.010 μg L-1 for arsenate (As5+) and higher sensitivity compared with literature. The mean percentages of species in the ten rice varieties were 16% (As5+), 65% (As3+), 24% (DMA) and 12% (MMA). Strong positive correlation coefficients (higher than 0.700, p<0.05) were found for As and Cd with other elements. The analyzed varieties presented higher levels of Fe, Zn and Co as well as low levels of As and Cd when compared with other studies, so they may be a basic source for genetic improvement. The mean estimated daily intakes through rice consumption were 3.88 μg for As, 0.43 μg for Cd, 5967 μg for Fe, 92039 μg for Mg, 2124 μg for Mn, 1875 μg for Zn, 2.88 μg for inorganic As and 0.92 μg for DMA. Our findings demonstrated that the consumption of rice varieties assessed by this study may effectively increase the daily consumption of Fe and decrease the daily intake of As among the Brazilian population.