Several years ago we did a poster presentation about
stability of ppb and sub ppb standards. If you send me your
mailing address, I will be glad to send you a copy of this
presentation. You can send it directly ([log in to unmask])
rather than through Plasmachem.
Some things we observed were:
1.) 2 ppb standards, prepared in 3% HNO3, stored in
either polymethylpentene (PMP)
or low density polyethylene (LDPE)
containers were stable for about two months.
An elemental exception is aluminum. It may have
leached out of the container.
2.) 10 ppt (parts per trillion) standards in dilute nitric
acid, stored in PMP or LDPE were stable for
about four hours. After this time, the concentrations
of several elements, most notably zinc, increased.
This may have been due to contamination entering
through the porous plastic container walls.
The same 10 ppt standards showed increased
stability in perfluoroalkoxy (PFA) Teflon containers.
PFA is not as porous as the other plastics and
did not allow airborne contamination to pass through.
Interestingly, PFA tended to adsorb Mn quite rapidly.
Best of luck.
Steven A. Koch
Hopewell Jct., NY 12533
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