A stock reference solution of 1000 mg L−1 Hg in 0.3 mol L−1 HNO3
Titrisol® (Merck, Darmstadt, Germany) was used to obtain analytical
curves. Analytical grade reagents employed in the preparation of
extracting solutions were 37 wt.% HCl, 69 wt.% HNO3 and 70 wt.%
HClO4 (Vetec, Rio de Janeiro, Brazil). The extractions were performed
in 15-mL closed glass tubes.