Briefly, 0.8 g of ground wheat grains were cold digested
with ultrapure concentrated HNO3 (9 ml) over night in tubes before
heating. Hydrochloric acid (HCl) was added during two stages
of digestion (0.4 ml + 0.2 ml finish) under a controlled regime in an
open vessel (75 ml borosilicate glass tube), and the final volume
was made up to 25 ml. Generally, digestion was conducted for 5–
6 h with the maximum temperature not exceeding 140 C. Mineral
concentration (mg kg1) is expressed on a grain dry weight basis.