Materials and Reagents

1. Rice sample: Polished rice or brown rice
   
2. 10% HCl (Sigma-Aldrich, catalog number: 7647-01-0 )
   
3. 65% HNO₃ (Sigma-Aldrich, catalog number: 7697-37-2 )
   
4. 72% HClO₄ (Sigma-Aldrich, catalog number: 7601-90-3 )
   
5. 6 mM HCl (Sigma-Aldrich, catalog number: 7647-01-0) (used for the reduction of SeO₄^2- to SeO₃^2-)
   
6. Selenium standard solution (Sigma-Aldrich, catalog number: 7782-49-2 ) (1, 5, 10, 20, 50, and 100 μg/L)
   
7. Acid mixture: HNO₃: HClO₄ (V/V) = 4:1
   

Equipment

1. Digestion tube (see Design digestion tube)
   
2. 40 mesh nylon sieve (15 cm diameter)
   
3. A paper bag (8 x 10 cm)
   
4. Parafilm (Parafilm, catalog number: PM-996 )
   
5. Volumetric flask (25 ml)
   
6. Glass stopper (match 25 ml volumetric flask)
   
7. Atomic fluorescence spectrometer (AFS) (model number: BRAIC AFS 610A )
   
8. Inductively coupled plasma mass spectrometry (ICP-MS) (PerkinElmer, model number: ELAN-DRCe )
   

Procedure