Thus, the un-combusted material
was removed from the boat using a brush, and then a
flame was
employed to heat the boats and remove any trace of Hg. For the
quartz boats, the decontamination was carried out by immersing in
a 10% HNO3 solution overnight, followed by rinsing with ultrapure
water. Sometimes, the analysis of samples with high mercury
content can also contaminate the catalyst or the amalgam, causing
a memory effect and demanding a cleaning step. In this case, a
cleaning cycle consisting of the analysis of about 100 mg of wheat
flour followed by the analysis of an aliquot of 100 mL of 5% (v/v)HNO3 solution is required.