Conventional digestion method (CDM)
About 0.5 gm of five replicates samples were
taken separately in pyrex flasks (50 mL in capacity), the
contents of flasks were treated with 2 mL mixture of
acid and oxidant (65% HNO3 and 30% H2O2) in the
ratio of (1:1, v/v) for decomposition of organic matter.
The contents of flasks were heated on electric hotplate
at 80 0C, for 2–3 hrs, till clear. The resulting solutions
were evaporated to semidried mass and than final
solutions were made up to 25 mL with 0.2 M HNO3, for
the determination of Cd, Ni and Pb by ETAAS. Blanks
(without sample) were carried through the complete
procedure of both methods. The concentrations were
obtained directly from calibration graphs after
correction of the absorbance for the signal from an
appropriate reagent blank. All experiments were
conducted at room temperature (30°-35°C) following
well-established laboratory protocols. The blanks were
always prepared in same manner as samples. The
digests obtained by both methods were subjected to
ETAAS.