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New USP 233 for Os analysis

Advice by Paul Gaines, Ph.D.

Even in an HCL only acidified (water) matrix we still see the false high results for Os which you discuss in your Periodic Table. It can be seen in the intensities for each rep reading we run on the same sample. Blanks run between samples bring the Os intensity to the initial blank reading. Do you have any advice to get around this constant intensity creep for Os?

First - Keep the following in mind when working with osmium:

  • Os should not be exposed to any oxidizing agents to avoid the formation of OsO4. The tetroxide is very volatile and toxic.
  • A common mistake is to dilute Os containing solutions with solutions containing nitric acid. Tetroxide formation is slow but will cause false high readings due to the increased amount of the gaseous tetroxide reaching the plasma.
  • Only work with Os in HCl containing solutions and use a separate waste container. Check with your safety coordinator or manager before using and attempting to dispose of Os.
  • Use glass introduction systems if at all possible when measuring Os. The washout times from plastic introduction systems are slower.

If you have observed all of the above and are still having problems I have found that adding APDC (ammonium pyrrolidine dithiocarbamate) will complex with the tetroxide eliminating the false high reading. My approach was to just add a few mg of the powder to the sample and mix well - it was messy but was quick and worked. You may want to take the time to refine the approach. Please feel free to call me with any questions or discussion.

Serving you in chemistry,
 

Paul R. Gaines, Ph.D.
CEO of Inorganic Ventures & Fellow Chemist

DISCLAIMER: Advice offered by the chemists at Inorganic Ventures is intended for the individual posing the question. Feel free to contact us to verify whether these suggestions apply to your unique circumstances.