I would think that it depends on the type of analysis you are doing.
For instance, when you validate a method for, lets say assay of lidocaine for example, you typically validate the method to determine lidocaine...period. In my experience your method isn't validated to determine lidocaine from supplier XYZ only.
However , for instance, if the new material has potential new impurities this opens a new can of worms as you would need to confirm that you aren't seeing coelution, poorly separated peaks, etc. Make sure to have the supplier give you a list of potential impurities and compare that to your current API
My recommendation would be to obtain some of the material and do your typical raw material testing on it for feasibility of its use. This way, if there are any issues with the material you can (hopefully) identify them before going through the stages of raw material qualification, stability studies, etc. Identify if the material can conform to your specifications for the current supplier and predetermine if there are any risks associated with the new supplier's material.
