Stability of Elements at ppb Concentration Levels

Summary of Findings

• The 1 % nitric acid solutions of the alkali, alkaline, and rare earth elements do not show any instability at the 2-100 ppb level in LDPE.
• The majority of elements studied were found to be stable for 1 year at the 2-100 ppb level.
• Silver (Ag) is the only unstable element found that is stable at the 2 ppb level. Ag's instability is most likely linked to its chloride chemistry (photo-reduction, precipitation).
• Gold (Au) and Mercury (Hg), which are similar in stability, are the most unstable elements and are the only elements unstable at all of the concentration levels studied. They are also reported to stabilize one another.
• Platinum (Pt), Tantalum (Ta), Molybdenum (Mo), Tin (Sn), Hafnium (Hf), and Iridium (Ir) were originally present as a fluoride or chloride complex.

Additional studies are planned for the stabilization of Hg and Au at the ppb level and will be reported when complete. It is hoped that conditions can be found that will stabilize these elements, making LDPE (the cleanest of plastics) as the preferred container material for the containment of all of the elements at the ppb concentration level.

1. A Handbook Of Decomposition Methods In Analytical Chemistry; Hasted Press: New York, 1979.

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