[Nhcoll-l] Formalin transfer

Thu Sep 22 19:02:51 EDT 2022

Hi Mandy,
That is a great question - what, if any, is the optimum amount of formaldehyde to carry over into storage solutions?
My credibility, again if any, is with physical chemistry of solutions and ends abruptly at the solution-specimen interface.
Going beyond that, I must defer to John, Dirk, et al.
I do hope they will have some evidence based advice on what would be an ideal residual concentration of formaldehyde, recognizing that would likely depend on taxonomic group being preserved.
Rob

From: Mandy Reid <Mandy.Reid at Australian.Museum>
Sent: Thursday, September 22, 2022 4:53 PM
To: Robert Waller <rw at protectheritage.com>; nhcoll-l at mailman.yale.edu
Cc: Rhiannon Stephens <Rhiannon.Stephens at Australian.Museum>; Harry Leung <Harry.Leung at Australian.Museum>
Subject: RE: Formalin transfer

Hi Rob
Thank you very much for that advice. That is really helpful.

I also received the below response. Do you think flushing the formalin from tissues could reverse the cross linking and hence fixation of the specimen? It seems to me that if this is the case, rinsing the surface formalin and then transferring through an ethanol series would have exactly the same effect in the long term as soaking the specimen out in water, so I am not sure of the advantage of only rinsing the surface of the specimen as stated by Andrew below. It assumes that no liquids subsequently enter the specimen when I imagine it would ultimately reach equilibrium with the preservative.

We don't go through an ethanol series because of the time involved and also because it would require huge volumes of ethanol.

Do you have a recommended procedure for transferring specimens from formalin to ethanol or do you think simply soaking out in water (lids on) then placing straight in 80% ethanol is OK in terms of the longevity and integrity of the tissue?

Cheers
Mandy

Hi Mandy,

Interesting - we only wash the surface formalin off before running through stepping alcohol. The information we'd always worked to was that flushing all formalin out of the tissues was undesirable long term (especially with small fishes), as the cross-linking caused by formalin can be partially reversed. There is an equilibrium reaction between aldehyde & alcohol forming acetal & water. Do you have more recent and improved info on changing this process?

I can't see

Cheers
Andrew

>><<<)o>
Assistant Curator NE (Fishes)
Museum of New Zealand
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027 7339363

Dr Mandy Reid
Collection Manager | Malacology
Australian Museum  1 William Street Sydney NSW 2010 Australia
T 61 2 9320 6412 M 61 0431 829 842
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From: Robert Waller <rw at protectheritage.com<mailto:rw at protectheritage.com>>
Sent: Thursday, 22 September 2022 11:57 PM
To: Mandy Reid <Mandy.Reid at Australian.Museum<mailto:Mandy.Reid at Australian.Museum>>; nhcoll-l at mailman.yale.edu<mailto:nhcoll-l at mailman.yale.edu>
Cc: Rhiannon Stephens <Rhiannon.Stephens at Australian.Museum<mailto:Rhiannon.Stephens at Australian.Museum>>
Subject: RE: Formalin transfer

Hi Mandy,
The vapor pressure of formaldehyde in aqueous solutions that are less than 40%w/v is real (we can smell it) but considerably lower than the vapor pressure of water in the solution. Therefore, unless the surrounding atmosphere is very close to 100%RH (speculating, perhaps > 99%), then water will be leaving the solution faster than formaldehyde does. Therefore, keeping a lid on makes more sense than leaving it off if the goal is extracting formaldehyde while keeping formaldehyde concentration as low as possible in the solution.
Best,
Rob

From: Nhcoll-l <nhcoll-l-bounces at mailman.yale.edu<mailto:nhcoll-l-bounces at mailman.yale.edu>> On Behalf Of Mandy Reid
Sent: Wednesday, September 21, 2022 9:17 PM
To: nhcoll-l at mailman.yale.edu<mailto:nhcoll-l at mailman.yale.edu>
Cc: Rhiannon Stephens <Rhiannon.Stephens at Australian.Museum<mailto:Rhiannon.Stephens at Australian.Museum>>
Subject: [Nhcoll-l] Formalin transfer

We are currently working on a large project at the Australian Museum to transfer our entire mollusc collection out of formalin (in which it has been stored for historical reasons) and into ethanol for long term preservation.

We normally soak each specimen lot out in 3 changes of water in a fume hood with lids left off the containers/vials etc. to assist with degassing of the formaldehyde in solution. Our problem is a bottleneck in our workflow due to limitations imposed by our fumehood work space. I am wondering whether others in the group have faced similar issues and whether soaking out can possibly be done in water but leaving the lids on the containers (hence could be done on a lab bench after pouring off the formalin in the fume hood)? We don't have a way to measure residual formalin after the soaking-out process so don't know whether or not this will be effective.

Any advice would be much appreciated.
Mandy

Dr Mandy Reid
Collection Manager | Malacology
Australian Museum  1 William Street Sydney NSW 2010 Australia
T 61 2 9320 6412 M 61 0431 829 842
[signature_357450491]<http://www.australian.museum/>
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