Mercury measurement
Two milliliters of each urine sample were mixed with 0.1 mL
of 35% w/w nitric acid, 0.2 mL of 50% w/w sulfuric acid and
0.5 mL of 5% w/v potassium permanganate, then the samples
were submitted to microwave digestion at an elevated temperature
for 15 minutes. The sample solution was allowed to
stand at room temperature. If the solution’s color changed from
purple to brown, then a further 0.5 mL of permanganate solution
was added, mixed, and allowed to stand for 15 minutes.
This process, of adding successive aliquots of permanganate
solution and allowing the reaction to proceed, was maintained
until the purple color was sustained