How can I detect the difference between biotic and abiotic compounds in a soil?

I’m working with some samples in a soil lab and have been asked to propose a hypothesis about the difference between a sample with life in it and a sample with no life in it. I have searched the literature but there is no straight-forward answer to this that I have seen.

I think there are some compounds which are only formed from organic processes and others which are only formed from inorganic processes. So I think this is a starting point. But I don’t know what those processes and compounds are.

Can someone give me a shove in the right direction?