The dry ashing was done using the Uniscope muffle furnace
(model SM 9080, Surgifriend Medicals, England), while the wet digestion was done using the Digestion System 40, 1000 heating
unit of JC Tecator. A Buck Scientific Atomic Absorption Spectrophotometer
(210 VGP model, East Norwalk, Connecticut, USA) was
used for determination of the metals. The determination was
carried out in an air/acetylene flame. The operating parameters
for the elements determined were set as recommended by the
manufacturer and they are highlighted in Table 1.