Digestion of rice
To dissolve rice samples prior to ICP-MS analysis, 0.2 g of rice was mixed with 2.5 mL of sub-boiled HNO3 and 0.5 mL of H2O2 in a closed Teflon vessel (Savillex, Minnetonka, USA), followed by heating to 50 °C for 1 h. The resulting solution was then diluted to 20 mL with DDW.