If you have already powdered (ground or otherwise reduced the feathers to a dusty or powdery consistency), then keep them in that form until you are ready to test the samples. I assume you will be digesting them in acid or perhaps TMAH (trimethyl ammonium hydroxide, given the protein levels likely to be found in feather).

I would stress that assuming your sample storage containers are "clean" is not always a good one to make. (For instance, I once had a PTFE bottle cap liner custom made for our lab which had 20 parts-per-billion lead. Not much in the grand scheme of things, but it would be more than enough to distort the findings of a heavy metal survey such as yours.) As long as the digest vials are clean you can use anything that will withstand the temperature

If nothing else, test an unused container (or multiple randomly selected tubes) for contamination with blank digest solution (dilute acid for example) and check that there is nothing of interest present in your containers.

While you're at it, test your gloves, scissors or scalpels and cutting boards, and anything else that has come into contact with the feathers.

Especially test the grinder: small (microscopic) particles can chip from the blades and create random spikes of iron/nickel/chromium etc. depending on the metal composition which may leave you wondering what was happening to your birds. Using a low-element sample such as rice grain will help you check for residual carry-over of elements between samples. Run 5 or 6 rice samples in a row after a feather sample and see if there is any element(s) that persist(s) after the first rice blank. That will help you trace any grinder contamination from a "high element" feather sample into the following "clean" feather sample.

Thank you for your answer, would it be possible to clarify these points please. If I understand correctly I can use other tubes unless they will be clean and contain no contaminants for conservation if this is the case what bottles do you suggest to me, however for digestion it is absolutely obligatory to use teflon bottles

You can use polypropylene (PP) or Polystyrene (PS). These are fairly cheap, generally clean and available in different sizes for however large your samples are. 10ml vials should hold more than enough of a subsample for ICPMS purposes. *Note that coloured caps can be a source of metals at times, so natural/translucent is probably the safest option. Test some by rinsing with acid for 24-48h and seeing what metals (if anything) comes out during this time.

Now for some clarification; why did you ask if you "can use tubes other than Teflon for digestion" if you now say it is "absolutely obligatory"? Either way, test the Teflon digestion vials for potential contamination to confirm your method is suitable for the metals you want to analyse. If they are re-usable vials, you might have to run several cleaning cycles to be sure you have leached the previous samples' contamination from them. Microwave digest systems often require this for "sticky" elements.

I'm asking because I can't get the teflon tubes, so I'm looking for something to replace them with. Thank you for your answer.