[Histonet] Formalin (from Paraformaldehyde) stability

Geoff McAuliffe mcauliff <@t> umdnj.edu
Mon Mar 3 13:20:34 CST 2008

Hi Teri:

    Formalin made from paraformaldehyde is stable for some time, at 
least a few days if not longer. Someone has published on this but I 
don't remember who.
I used to make my fix fresh each day, it just is not necessary.


Johnson, Teri wrote:
> I had a question today from a researcher asking about the stability of a
> formalin solution made from Paraformaldehyde. She indicated that on one
> of her samples, freshly prepared fixative worked well, while one day old
> fixative (same batch) did not fix properly. She assures me all
> pre-fixative steps were the same. The samples were fixed for 2 hours. I
> have no details about her experiments or what she was testing (I suspect
> mRNA targets). 
> I realize that without the addition of methanol, the solution is not as
> stable would would re-polymerize with time. I'm wondering if the
> fixative started re-polymerizing and that made the difference, but one
> day? Is it possible for one day to make the difference between a
> positive and negative result? 
> How stable/instable is methylene glycol?
> I'm also thinking that by adding methanol (or using purchased 100%
> formalin (37% formaldehyde)) would be useful for mRNA targets, since
> aldehydes tend to fix nucleic acids poorly.
> Why do all my most difficult questions arise on Friday afternoon?
> Thanks for any insight you can give me.
> Teri Johnson, HT(ASCP)QIHC
> Managing Director Histology Facility
> Stowers Institute for Medical Research
> 1000 E. 50th St.
> Kansas City, MO 64110
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Geoff McAuliffe, Ph.D.
Neuroscience and Cell Biology
Robert Wood Johnson Medical School
675 Hoes Lane, Piscataway, NJ 08854
voice: (732)-235-4583 
mcauliff <@t> umdnj.edu

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