ICP Standards: Molybdenum and Titanium Stability; Mercury Volatility
Richard wondered whether Mo and Ti are stable for any length of time without using HF? He also wanted to know what is meant by the term "trace HF"?
Meanwhile, John noted that hot block digestions of a clean acid water matrix with inorganic mercury standard added to a final concentration of 0.5ug/L, resulted in mercury recoveries ranging from 75-80%. He asked if inorganic mercury is volatile enough to explain such a loss.
Both Ti and Mo are stable in HCl. The lower in concentration you go, the better the chances of achieving solubility with any of the mineral acids.
There is no set definition for trace HF. We consider anything less than 1000 ppm HF to be "trace HF."
Our experience with Hg is that it will readily adsorb onto plastic container walls at the ppb level in nitric acid. Therefore, the loss is likely after the digestion, i.e., after the digestate is transferred to a plastic container (some could be adsorbed at the sub ppb level during digestion in Teflon, glass or quartz).
Please contact me if you have any other questions.
Serving you in chemistry,
Paul R. Gaines, Ph.D.
CEO of Inorganic Ventures & Fellow Chemist
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