The sample preparation for chemical analysis is a required stage
for many analytical techniques, which consists in transforming the
sample into an appropriate form for the analysis. For the elemental
analysis, the solid samples are usually changed to solutions, which
carry the analytes free of organic matter. This step is usually the
most time consuming analytical procedure, in addition to generating
toxic residues and increasing the probability of sample contamination
(Reyes, Rahman, & Kingston, 2009).