Common Problems with Hg, Au, Si, Os and Na

This part of our ICP Operations guide provides some suggestions when attempting to work with mercury, gold, silicon, osmium, or sodium.

Mercury (Hg)

A common problem with Hg is stability. For an overview of Hg stability please our article entitled Mercury Chemical Stability. In March of 2003, the EPA published a bulletin describing the use of Au to stabilize Hg solutions: Mercury Preservation Techniques. When working at the ppb level we have found that using HCl rather than nitric acid will maintain the stability of Hg⁺² solutions in plastic (LDPE) containers.

Another problem with Hg is loss during sample preparation. When performing acid digestions, the use of closed vessel digestion or the use of condensers should be considered. Ashing should be avoided. Only use validated sample preparation procedures.

Here are some additional suggestions when working with mercury:

• The presence of reducing agents in the solution may reduce Hg to the metal causing false high results due to the volatility of the element where the introduction system delivers more Hg to the plasma as a result.
• The use of plastic introduction systems will cause unusually long washout times. Glass is preferred and the use of HCl rather than nitric acid will reduce the washout time.
• The use of nitric acid matrices for ppb Hg determinations by ICP-MS should only be attempted using Au as a stabilizing agent (see above link).

• Hg elemental data

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