Frequently Asked Questions
How do I minimize mercury losses during digestion?
Typically, a small amount of concentrated HCl added to the sample pre-digestion will complex any free mercury before, during and after the digestion process.
What kinds of batteries contain mercury and why was it added?
Mercury is known to be toxic to plants, animals, and the environment. A variety of older button-cell batteries contain mercury. Button-cell batteries are small, thin, and not rechargeable. They are used mostly in watches, toys, and hearing aids.
Gas can form in button-cell batteries due to the corrosion of zinc. This corrosion can cause electrolysis and generate hydrogen gas. Build-up of hydrogen gas can cause the battery to leak and quit working. Mercury suppresses zinc corrosion, which is why it was added to button-cell batteries. Technological advancements have allowed for the phasing out of added mercury without losing energy capacity or increasing prices.
Which acids should be used for sample preservation and sample digestions?
Often the prescriptive language of U.S. Environmental Protection Agency methods prohibits changes to sample preservation techniques or hold times. These are typically using small volumes of HNO3 to bring the pH <2. Others use HCl or bromine monochloride (BrCl) solution, which is made with concentrated HCl. However, for the sample digestion it is often permissible to substitute equivalent chemical types if quality is still assured. Teledyne LABS always advises using 3% HCl as the diluent for Hg working standards or sample dilutions on its QuickTrace systems. The HCl forms a complex with the mercury, which keeps the Hg in solution more effectively compared to using HNO3. This will provide consistent and reproducible results when analyzing for mercury.
