PFA - does it have to be immediately chilled? - (Jul/30/2012 )

Hi all

Currently attempting to climb the vertical learning curve that is EngD year 1 and I was wondering if someone could help. I made some 4% PFA for the first time today, for the purpose of fixing some cells for FISH. The protocol said that after heating the water / PBS and dissolving the paraformaldehyde the solution should be chilled on ice. Is this purely to prevent the PFA "going off" or is it a vital part of the procedure? I ask because I'm stupid and I forgot to immediately chill it, however I did aliquot the PFA and get it in the freezer within 30mins of making it.

Thanks for your advice.

It will be fine, it is stable in the fridge for about a week and well over 6 months at -20 C. Chilled fixatives are often used to slow the cell processes and the rate of action of the fixatives during use.

Excellent. Thank you!