Re: Shelf life of 4% formaldehyde solutions

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Date:Wed, 4 Aug 1999 12:14:52 -0400
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 Formaldeyhyde has the methanol additive for stabilization which would
carry over into the 10% formalin when prepared.  This would be true even if
purchased prepared.,

We used 10% formalin fixed tissue on paraffin sections for IHC with no ill
effects unless the procedure called for a different fixation such as frozen
sectioning.  The important part here, is to not let the tissue overfix in
10% formalin.

A good recommendation for determining expiration on all chemical would be
too look at the MSDS sheet for decomposition information.  My suggestion
would be to try to obtain an MSDS from a manufacturer who is producing 4%
formalin.  If this information is not available than
 I can offer an MSDS for 10% formalin if that would be helpful.

"Karen D. Larison" <> on 08/03/99 09:11:48 PM

Subject:  Re: Shelf life of 4% formaldehyde solutions


Formalin has additives such as methanol to keep the formaldehyde from
polymers and precipitating from solution.  Therefore its shelf life is
longer than
pure formaldehyde.  Most people avoid using formalin-based fixatives when
IHC, simply because additives such as methanol may have an adverse affect
on the
epitope.  Most people instead use a 4% paraformaldehyde solution made up
fresh in a
phosphate buffer.  The shelf-life on this quite short.  You'll notice
forming in this fixative in about a week, even when stored refrigerated.

Karen in Oregon

Date:          Tue, 3 Aug 1999 13:51:11 -0500
From:          "LOVE, JOHN E. (JSC-SD)" <>
Subject:       Shelf life of 4% formaldehyde solutions
To:            "''"

I understand that the shelf life of formaldehyde solutions is affected by a
variety of reactions including oxidation, methanol formation,
polymerization, and condensation.  I am interested in finding out about the
shelf life of buffered 10% formalin (4% formaldehyde) solutions stored at 4
degrees C.
Thank you for your help.

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