It would be best if you were more specific. There isn't a single type of capsule for Mössbauer samples. Also, what kind of sample? Is it radioactive? Sensitive to oxidation? In powder form, etc. An image would be helpful, too.

Thanks for the reply, Amir. Here is the picture of my capsule. The sample is non-toxic or radioactive. It contains 57Fe bound protein dissolved in aqueous buffer. It is not sensitive to oxidation. It is safe to work with it on the bench top at room temperature. I would like to figure out a way to open this type of cap without breaking it. It would be better if I can recover the sample at the same time. But I can recover it by pushing the cap down to the bottom within a clean container. Anyway, the top priority goal is to open it in a recycling way. Thanks for any comment or suggestion.

I think I figured out a way to do this. Use a needle nose plier to attach from inside, then pull out.