Samples preparation and analysis
In this investigation atomic absorption spectrophotometry
after dry ashing was performed based on AOAC official method 999.11 (Jorhem, 2000).
Rice samples were dried at 105 C for 48 h.
Rice samples were ashed at 450 C under gradual increase (650 C/h).
6 M HCl (1 + 1) is added,
and the solution was evaporated to dryness.
The residue is dissolved in 0.1 M HNO3 (Jorhem, 2000). The
digested solution was analysed for Pb, Cd, Cr, Ni and Co, contents
by flame and graphic furnace atomic absorption spectrometer (Shimadzu
AA-680, Kyoto, Japan; Shimadzu MUV-IA, Kyoto, Japan). All
of the samples were digested as triplicate. Each sample was analysed
three times. Concentrations of trace metal in samples were
expressed in terms of mg kg1 on a dry weight basis (Jorhem,
2000).
2.