How can a scientist assess whether a pure niobium Nb sample is responsible for contaminating the lab with radioactivity?

Pure niobium is not radioactive, so radioactivity could indicate that the sample has been changed by nuclear reactions that produced other elements. Testing whether the sample contains elements besides niobium directly checks for that possibility. Heating or pressurizing it would not reliably show whether the sample is the source of the radioactivity, and niobium oxide compounds contain niobium and oxygen but are not evidence of radioactivity.

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