[LabTech]

In my lab, we use a CEM automated microwave peptide synthesizer.  We have been having trouble with amino acids precipitating out after a few days.  We realized that the problem was dimethylamine in the DMF was prematurely cleaving off the Fmoc group, causing the amino acids to crystallize.  After looking for ways to obtain pure DMF that is suitable for peptide synthesis (avoiding the expensive peptide synthesis grade DMF from Fisher), I came across a Nature Protocols paper, in which they use biotech grade solvent and store it over Dowex Ion Exchange resin.  Since, it is not possible to have the resin within the DMF container that is connected to the machine, we can store the DMF over the resin, but we will to filter off the resin before transferring it to the DMF container.  Does anybody know how long the DMF should remain dimethylamine-free for after filtering off the resin?  I would like to know, so that I can determine whether or not it is okay to fill the DMF container to full capacity (40 L) or whether we can only put just enough DMF to synthesize the peptides that we are making in the near future.  Thanks!   

[Two00proof]

In my experience, DMF is extremely stable as long as you protect it from heat, light and air.  So if your 40 liter keg is kept under an inert atmosphere, it should be fine for a long time.

If it's not under argon or some other inert gas, I would only put in enough to do single runs, and I'd think about buying a smaller container.