United States Grown and Imported Rice on Sale in Las Vegas: Metal(loid)s Composition and Geographic Origin Discrimination.

Concentrations of metal(loid)s, Ag, Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Se, Sr, V and Zn, were determined in rice on sale in Las Vegas. The rice samples were grown in five different countries, the USA, Thailand, India, Pakistan, and Bangladesh. The elemental concentrations in rice grain were determined using inductively coupled plasma mass spectrometry (ICP-MS) following hot block-assisted digestion. The accuracy of the laboratory procedure was verified by the analysis of rice flour standard reference material (NIST SRM 1568b). The mean metal(loid) contents in rice of various geographic origins were 3.18-5.91 mg kg for Al, 0.05-0.12 mg kg for As, 3.64-41 μg kg for Cd, 5.11-12 μg kg for Co, 0.12-0.14 mg kg for Cr, 1.5-1.91 mg kg for Cu, 3.04-4.98 mg kg for Fe, 4.2-10.4 mg kg for Mn, 0.21-0.41 mg kg for Ni, 0.02-0.07 mg kg for Se, 0.68-0.88 mg kg for Sr, 3.64-5.26 μg kg for V, and 16.6-19.9 mg kg for Zn. respectively. The mean concentration of As in US rice was significantly higher than in Indian, Pakistani, and Bangladeshi rice. On the other hand, it was found a significantly low mean level of Cd in US-grown rice. It was also found that the concentrations of metal(loid)s in black and brown rice on sale in Las Vegas were statistically similar, except for Mn and Se. The geographic origin traceability of rice grain involved the use of ICP-MS analysis coupled with chemometrics that allowed their differentiation based on the rice metal(loid) profile, thus confirming their origins. Data were processed by linear discriminant analysis, and US and Thai rice samples were cross-validated with higher accuracy (100%). This authentication quickly discriminates US rice from the other regions and adds verifiable food safety measures for consumers.