After digesting and extracting the samples until become transparent solution,
the digested samples were analyzed by inductively coupled plasma optical emission
spectrometry, VISTA-MPX Axial (ICP-OES) to estimate the type and the
concentrations of heavy metals. Mixed standard (23 elements) was used to evaluate
heavy metal as barium (Ba), cadmium (Cd), chromium (Cr), manganese (Mn), nickel
(Ni), lead (Pb)