[Histonet] PFA preparation

[Merced Leiker]

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 
<AnthonyH <@t> chw.edu.au> 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: histonet-bounces <@t> lists.utsouthwestern.edu
> [mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of
> ejschmid <@t> ucalgary.ca
> Sent: Sunday, 7 December 2008 7:30 AM
> To: histonet <@t> 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
Research Technician II
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School of Medicine and Biomedical Sciences
State University of New York at Buffalo
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