Determination of mercury in rice by cold vapor atomic fluorescence spectrometry after microwave-assisted digestion

A cold vapor atomic fluorescence spectrometry method (CV-AFS) has been developed for the determination of Hg in rice samples at a few ng g(-1) concentration level. The method is based on the previous digestion of samples in a microwave oven with HNO3 and H2O2 followed by dilution with water containing KBr/KBrO3 and hydroxylamine and reduction with SnCl2 in HCl using external calibration. The matrix interferences and the effect of nitrogen oxide vapors have been evaluated and the method validated using a certified reference material. The limit of detection of the method was 0.9 ng g(-1) with a recovery percentage of 95 +/- 4% at an added concentration of 5 ng g(-1). The concentration level of Hg found in 24 natural rice samples from different origin ranged between 1.3 and 7.8 ng g(-1). (C) 2010 Elsevier B.V. All rights reserved.