We are making up a new enriched isotope spike mixture for determining
several trace metals in seawater by isotope dilution. We are starting
fresh, with powders obtained from Oak Ridge. The powders are oxides (111Cd,
57Fe, 65Cu, 68Zn), carbonates (206Pb), and metal powder (62Ni).
We are about to start dissolving these very carefully in appropriate acids.
Can anyone with experience with this process give us tips so we don't have
problems with dissolution or the stability of the resulting single-element
solutions? If there is a literature methods source that we should know
about, please let us know! In particular:
1. What acid type and strength for what metal and compound? Any problems
or considerations getting the oxides into solution?
2. Is it recommended to use heat or other physical treatment (sanitation?)
to aid in dissolution?
3. Is there a recommended acid strength and metal concentration for best
storage of a relatively concentrated stock solution? We want to keep these
4. How reliable is the stoichiometry of the compounds? Can mass
determination tell us moles of metal to within 1%? 5%?
5. Should we dry the powder (in the original glass vial) at 105°C before
6. Has anyone had problems with the true isotopic composition not matching
that on the certification sheet from Oak Ridge?
Thanks VERY much for any tips you can give on this process. We want to
start this within the next day or two, and we want to avoid mistakes!
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Institute of Marine and Coastal Sciences and Department of Earth and
71 Dudley Road
New Brunswick, NJ 08901-8521
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