Purging every imaging sessions seems to be a lot of work
According to the manual, Argon in a QSI camera should last about three years and after that they recommend baking the canister with desiccant every six or so months.
The one I've got is apparently pure without additives/contaminants, it is food grade and ISO9001 certified. Thank you for the hint with gasweld canisters
but hopefully I wont need Argon for the next few years