We routinely add paraformaldehyde to alkaline water at room temperature
while stirring and wait only about 30-60 mintues for it to dissolve. Then
we add a concentrated amount of PBS up to the total required volume (so
that the buffer is 1x in the final volume). Then we add acid to bring the
pH back down to 7. Then we filter it since not all of the PFA has
dissolved (though most of it has).
Merced
--On Monday, December 08, 2008 9:11 AM +1100 Tony Henwood
<[EMAIL PROTECTED]> wrote:
My experience is that when you add paraformaldehyde to water all it
forms is a colloidal solution (ie on standing, the paraformaldehyde
settles with very little going into solution (personal experience,
waited one week, then gave up).
Has your experience been different?
Regards
Tony Henwood JP, MSc, BAppSc, GradDipSysAnalys, CT(ASC)
Laboratory Manager & Senior Scientist
Tel: 612 9845 3306
Fax: 612 9845 3318
the children's hospital at westmead
Cnr Hawkesbury Road and Hainsworth Street, Westmead
Locked Bag 4001, Westmead NSW 2145, AUSTRALIA
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of
[EMAIL PROTECTED]
Sent: Sunday, 7 December 2008 7:30 AM
To: histonet@lists.utsouthwestern.edu
Subject: [Histonet] PFA preparation
Hi,
So then what is the best way to prepare formaldehyde fixative from
PFA?
The way I have been taught, which differs from what I have read, is
to dissolve 4% into ddH2O at room temperature. After that one could add
PBS or buffer.
I've also been taught that too much heat during preparation
"degrades" PFA, and that PFA (or formaldehyde solution, rather) stored
too long will lose freshness because it "degrades."
What I read is different. Texts suggest to dissolve the PFA in warm
water, and that aging of the fix is due to repolymerization, not through
degradation.
What should i do?
Eric Schmidt
University of Calgary
Medical Sciences
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Merced M Leiker
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