The producer of the ab should have details on the buffer matrix. It may already have azide. If not you can spike a concentrate to obtain ~ 0.02% concentration.

Abs should be robust...however, Mabs may fall out of solution.

If antisera, you may see some clumping of other proteins.

Best bet is with next order make sure preservative is added before aliquoting.

Store your aliquotes at -70-80C

Good luck!

i'm with sgt4boston - store some at -80 and see how that works

dom