Dear Histonetters,
I would like to ask a question about paraformaldehyde, please.  I was
trained to make 4% paraformaldehyde in PBS fresh to use.  I remembered the
lab I worked for as an undergrad insisted on fresh daily made
paraformaldehyde solution.  And that was my job back then.  My question is:
Can I make stock 10% in 2.5X PBS and keep at 4 degree for sometime?  If yes,
how long can I store?  If no, what's the reason for not being able to do it
and have to make it fresh?  Will the molecule cross link themselves and
therefore reduce the fixative strength on tissues?
Thank you.
Su