Re: Shelf life of 4% formaldehyde solutions

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From:"Karen D. Larison" <>
Date:Tue, 3 Aug 1999 17:11:48 -0800


Formalin has additives such as methanol to keep the formaldehyde from forming 
polymers and precipitating from solution.  Therefore its shelf life is longer than 
pure formaldehyde.  Most people avoid using formalin-based fixatives when doing 
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 precipitate 
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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