[Danielle1]

Yesterday I have made a 50mM Tris-HCl solution from powder into destilled water. I am wondering if anyone knows how long I can safe this and at which conditions. Any suggestions?

Best Regards, Danielle

[Arkcon]

It will be hard to come up with a definitive answer for you.  A dilute solution, of this particular orgainic compound may not last very long at all, because it will be very susceptible to microbial attack.  I once answered a similar question, with many caveats, a long while ago:  http://www.chemicalforums.com/index.php?topic=29560.msg112551#msg112551

[Babcock_Hall]

The best I can do is a qualitative answer.  Tris buffers are less susceptible to microbial attack than, say, phosphate buffers.  I recall reading somewhere that Tris is a weak uncoupler of oxidative phosphorylation, which would tend to slow down aerobic microbial growth.  I don't have a citation on that issue at hand, however.  For short term use, a refrigerator is probably OK, but it is important to give any buffer sufficient time to reach temperature equilibrium.  For longer term storage, I would freeze, but then I would mix thoroughly when I thawed it out.  Arkcon made some very good points in the linked answer.