Removing Sodium Azide from a solution - (May/25/2011 )

I am working with carboxylated beads for attaching cells to it. This time when I ordered these beads, they came with a little amount of sodium azide in it. I cleaned the beads 3-4 times by centrifuging, but then also couldn't get rid of sodium azide, as my cells are dying faster than before. Any suggestions would be appreciated a lot.

Thanks

clean them through a filter (sintered glass or in a column) so that you can get a complete exchange of buffer.