[Histonet] quick question about formaldehyde
Jackie M O'Connor
Jackie.O'Connor <@t> abbott.com
Fri May 13 12:54:40 CDT 2005
Formaldehyde is a gas. Full strength formalin is 37-40% formaldehyde gas in water. 10% Formalin is in
effect 3.7 - 4% formaldehyde.
10% Neutral Buffered Formalin is just that - 10% formalin buffered to a
neutral pH, usually with sodium phosphates.
Jacqueline M. O'Connor HT(ASCP)
Assistant Scientist
GPRD Cancer Research
Abbott Laboratories, Abbott Park, IL
Jackie.OConnor <@t> abbott.com
LuAnn Anderson <ander093 <@t> tc.umn.edu>
Sent by: histonet-bounces <@t> lists.utsouthwestern.edu
05/13/2005 12:43 PM
To: histonet <@t> lists.utsouthwestern.edu
cc:
Subject: RE: [Histonet] quick question about formaldehyde
At 12:43 PM 5/13/05, LuAnn Anderson wrote:
>Hi Joyce,
>That is exactly what we were taught. formaldhyde=37% and formalin=10%
>LuAnn
>
>
>
>>For all my years I have believed that formaldehyde was the 37%
>>concentrate without buffers, and that formalin was 10% buffered... learn
>>something new every day! Thanks John! -----Original Message----- From:
>>John A. Kiernan [mailto:jkiernan <@t> uwo.ca] Sent: Friday, May 13, 2005
11:31
>>AM To: Weems, Joyce Cc: histonet <@t> lists.utsouthwestern.edu Subject: Re:
>>[Histonet] quick question about formaldehyde Dear Joyce, Formalin = 37%
>>formaldehyde; so no, it doesn't make a difference. Formalin is not
>>buffered; it does contain about 10% methanol, which is put in to retard
>>polymerization. When diluted to make a 4% formaldehyde fixative, the
>>methanol concentration is 1%. Buffering of the dilute solution offsets
pH
>>changes due to the Cannizzaro reaction. It also inhibits the formation
of
>>blood-derived "formalin pigment" which forms after fixation in an acidic
>>formaldehyde solution. Tim Morken is correct in saying we don't know the
>>extent of chemical change in 12 year-old formalin. The fact that there's
>>no expiry date sugggests that it's not much. For what it's worth, I've
>>used formalin that's more than 5 years old and fixation has been
>>OK. John Kiernan london,
>>Canada ---------------------------------------------- "Weems, Joyce"
>>wrote: > > Also, John said "formalin" - was the solution formalin or 37%
>>formaldehyde - without buffers? Would that make a difference? > >
>>Joyce > > -----Original Message----- > From:
>>histonet-bounces <@t> lists.utsouthwestern.edu >
>>[mailto:histonet-bounces <@t> lists.utsouthwestern.edu]On Behalf Of Morken, >
>>Tim - Labvision > Sent: Thursday, May 12, 2005 2:08 PM > To: 'John
>>Kiernan'; Andrea Grantham > Cc: histonet <@t> lists.utsouthwestern.edu >
>>Subject: RE: [Histonet] quick question about formaldehyde > > John, you
>>said " Small amounts of methanol and formate ions are not going > to
>>change the fixative properties." > > But after 12 years will it really
>>be a "small amount?" How do we know what > percentage of the solution
>>will have been converted? > > Tim Morken > > -----Original Message-----
>
>>From: histonet-bounces <@t> lists.utsouthwestern.edu >
>>[mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of John
>>Kiernan > Sent: Thursday, May 12, 2005 10:48 AM > To: Andrea Grantham >
>>Cc: histonet <@t> lists.utsouthwestern.edu > Subject: Re: [Histonet] quick
>>question about formaldehyde > > Two things could have happened to
>>unopened > formalin in 12 years: > 1. Polymerization (to
>>paraformaldehyde). This is > evident as a white precipitate. It
>>slightly > reduces the concentration in the liquid, > but that
does
>>not matter for fixation. > Polymerization is accelerated by low
>>room > temperature, and it is claimed that the > process can be
>>reversed by autoclaving(paper > in Stain Technol about 40 years
>>ago). > 2. Cannizzaro's reaction, in which 2 molecules > of
>>formaldehyde react together, producing > one molecule each of
methanol
>>and formic > acid. This happens in all formaldehyde solutions > and
>>causes lowering of the pH. This doesn't matter > if you make a
neutral
>>buffered fixative solution. > Small amounts of methanol and formate
>>ions are not > going to change the fixative properties. > Bottom
line:
>>OK to use, but be sure to check the > pH of the working fixative
solution
>>and adjust if > necessary. > -- > ------------------------------- > John
>>A. Kiernan > Department of Anatomy and Cell Biology > The University of
>>Western Ontario > London, Canada N6A
>>5C1 > kiernan[AT]uwo.ca > http://publish.uwo.ca/~jkiernan/ >
>>http://instruct.uwo.ca/anatomy/530/index.htm >
>>_______________________________ > Andrea Grantham wrote: > > > > One of
>>the labs here is closing and they have a case of formaldehyde, > >
37.5%,
>>that they are trying to give away. They have had it in their > > lab
>>since 1993. The bottles have not been opened. Is it still good to > >
>>use? Andi > >
>>..................................................................... >
>
>>: Andrea Grantham, HT(ASCP) Dept. of Cell Biology & Anatomy : >
>
>>: Sr. Research Specialist University of Arizona : >
>
>>: (office: AHSC 4212) P.O. Box 245044 : >
>
>>: (voice: 520-626-4415) Tucson, AZ 85724-5044 USA : >
>
>>:
>>(FAX: 520-626-2097) (email: algranth <@t> u.arizona.edu)
>>: > >
>>:...................................................................: >
>
>> http://www.cba.arizona.edu/histology-lab.html > > > >
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>>------------------------------- John A. Kiernan Department of Anatomy
and
>>Cell Biology The University of Western Ontario London, Canada N6A
>>5C1 kiernan[AT]uwo.ca http://publish.uwo.ca/~jkiernan/
>>http://instruct.uwo.ca/anatomy/530/index.htm
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