Preparation of quality control materials for the determination of mercury in rice.

This study was performed to determine the feasibility of using Hg-spiked rice as a quality control material for Hg content analyses. Rice was coated with halogen compounds prior to the addition of Hg to increase the homogeneity and stability, both of which are important factors in the development of reference materials (RMs), relative to currently available RMs. The coating materials CCl4, CH2CHCH2Br, and CH3I were used to generate Hg-spiked rice RMs at the desired Hg concentrations. The coating materials were tested to determine the extent to which they were able to affect the adsorption of Hg onto the rice. The in-lab prepared Hg-spiked rice RMs using proposed RM production method exhibited good homogeneity (within- and between-bottle) and stability (short- and long-term) with respect to the evaluated coating materials, storage temperature (20°C or 40°C), and storage periods (from 0 days up to 24 months).