After getting required grain size, the samples were
subjected to close vessel microwave digestion. 0.5 g
of the dried and ground sample was digested in a close
vessel with 5 ml HNO3 and 3 ml H2O2 followed by 3 ml
HCl (26%). After digestion, contents were transferred
into a 50 ml volumetric flask and the flask was made up to the mark with distilled water. Finally the contents
were shaken, filtered and made available for further
analysis.