One gram of
each dried sample was weighted into a porcelain crucible and dryashed
in a muffle furnace by stepwise increase of temperature up
to 500 C within 1 h and then leaving to ash at this temperature
for additional 12 h. The residue was dissolved in 1 M nitric acid, filtered
into a 25 mL volumetric flask using Whatman filter paper and
made up to mark with the nitric acid (1 M). The blank digests was
similarly processed. The recovery study of this analytical procedure