paraformaldehyde fix

David L. Haviland, Ph.D. dhavilan at IMM2.IMM.UTH.TMC.EDU
Wed Sep 24 16:29:59 EST 1997

At 15:57 9/24/97 -0400, Stan A. Baldwin wrote:
>I've had several people tell me that paraformaldehyde made in solution
>is no good after a couple of days.  I've used month old paraformaldehyde
>from the frig and it fixes tissue just fine for immunocytochemistry and
>general histology.  Does anyone know if there is some chemistry reason
>why para would "go bad" after a couple of days in the frig.


I too am interested in this.  I've always made a 2% stock of PF and kept
that dark and in the fridge.  I dilute what I need with PBS to a final of
1% PF.  I've kept the stock for months (like.. 6 months..).  In flow
cytometery, fixation alters the FALS and 90'LS of cells and drops them a
bit.  This alteration has not changed with time and I've seen no
significant effect on FITC signal over the months.  If PF has a very short
shelf life, then I figure that I've been very lucky.  I've gone through
about 6 batches of PF and what determines when I need to make more is when
I run out.

I'd be interested in other comments you receive.


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