[Babcock_Hall]

It is often the case that one dissolves enzyme inhibitors in DMSO and then introduces them into an aqueous solution.  I can imagine that degradation of DMSO is possible; for example, one could write a disproportionation reaction to dimethylsulfide and dimethylsulfone.  Does anyone have any experience or knowledge that pertains to DMSO purity?  Thank you.

[rolnor]

It seems very stable, even att 150°C decomposition is slow:
https://www.gaylordchemical.com/products/literature/physical-properties/

You have to scroll down to read this.

[Babcock_Hall]

https://cen.acs.org/safety/DMSO-poses-decomposition-danger/98/i36
https://journals.sagepub.com/doi/pdf/10.1177/1087057109335670

In the presence of another substance, there can be decomposition (first link).  However, these issues relate to heating, from what I can gather.  Over time (while waiting for a bioassay) compounds may come out of solution (second link).  Anecdotally, I have heard that this was a problem with a 50% DMSO solution in one instance.

[rolnor]

Often people dissolve the compounds in 100%DMSO and then dilute the solution with water, this way lipophilic compounds may precipitate over time. If you have very lipophilic compounds and want to test them at high conc. be aware of this risc. I have seen lipophilic compounds looking "active" in an assay but this was just a effect if the compounds precipitating.