I thought I heard something about 10% formalin causing more DNA/RNA
breaks than 4% paraformaldehyde.  Have I been having strange dreams
again?

The lowly post-doc ,


Jacqui


Jacqui Detmar, Post-doctoral Fellow
Samuel Lunenfeld Research Institute, 
Mount Sinai Hospital
25 Orde Street, room 6-1001 AJ,
Toronto, ON, Canada
M5T 3H7
 
phone:   416-586-4800 x5607
fax:        416-586-8588
email:     detmar@mshri.on.ca
 
-----Original Message-----
From: histonet-bounces@lists.utsouthwestern.edu
[mailto:histonet-bounces@lists.utsouthwestern.edu] On Behalf Of Monfils,
Paul
Sent: Wednesday, August 27, 2008 5:26 PM
To: histonet@lists.utsouthwestern.edu
Subject: RE: [Histonet] (para)formaldehyde

10% formalin and 4% paraformaldehyde are interchangeable for most
purposes (in histology at least).  However there are a couple of minor
differences.  First, commercial formaldehyde solution contains 37% to
38% formaldehyde.  Therefore diluting it 1:9 results in a solution
containing 3.7% to 3.8% formaldehyde, while a 4% solution of
paraformaldehyde in water contains a full 4% formaldehyde.  Secondly,
commercial formaldehyde solution contains 10% to 15% methanol as a
preservative.  Therefore diluting it 1:9 results in a solution
containing 1.0% to 1.5% methanol.  This is not a problem for most
histological applications, but it could be a problem in a procedure
where sources of methylation have to be avoided.  4% paraformaldehyde
solution contains no methanol - nothing but water and formaldehyde.


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