[Nhcoll-l] Increasing ethanol concentration in stages

Wed Aug 30 06:56:01 EDT 2023

Hi Robyn,

it depends a bit on the type of specimens, as Dries mentioned: you probably could go up faster with fish than with (delicate) marine invertebrates, i.e. with specimens with (more stable) cellular membranes, but it is definitely useful being careful and consider more and smaller steps, especially if the specimens were exposed to low alcohol concentrations and might have suffered from hydrolysis. The critical steps regarding osmotic shock and damage usually at concentrations above 60 %.

If the concentration was well below 40%, it might be useful to bring them up to 50% in short time to prevent unwanted microbial activity. If there are many specimens in your jars, you could split them up in more jars, especially if you have larger 'deposits' of small specimens in the lower half of your jars, because of unwanted layering of the alcohol.

Hope this helps,
Dirk

Am 25.08.2023 um 15:33 schrieb a.j.van_dam at lumc.nl<mailto:a.j.van_dam at lumc.nl>:
Dear Robyn,

There is a positive correlation between the depth of tissue penetration and the square root of time for fixatives/preservatives. Assuming ethanol would penetrate 1 mm into the tissue in 1 hour (some papers mention this figure for 100% ethanol as the penetration coefficient), it would penetrate in 25 hours (ca. 1 day) 5 mm, in 49 hours (ca. 2 days) 7 mm, and in 169 hours (ca. one week) 13 mm.

Of course, besides the thickness of the tissue, it also depends on the type of specimen and its tissue density. It will always be a bit of a guess, but the above calculation surely helps in defining a minimum time per transfer bath.

Kind regards,

Dries

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Van: Nhcoll-l <nhcoll-l-bounces at mailman.yale.edu><mailto:nhcoll-l-bounces at mailman.yale.edu> namens Robyn Cumming <robyn.cumming at qm.qld.gov.au><mailto:robyn.cumming at qm.qld.gov.au>
Verzonden: vrijdag 25 augustus 2023 04:04
Aan: nhcoll-l at mailman.yale.edu<mailto:nhcoll-l at mailman.yale.edu> <nhcoll-l at mailman.yale.edu><mailto:nhcoll-l at mailman.yale.edu>
Onderwerp: [Nhcoll-l] Increasing ethanol concentration in stages

Hi all

I have some wet specimens with ethanol concentration below what is desirable (50-60%) and am topping them up in stages of ~5% back up to 70% to avoid osmotic shock.

My question:  does anybody know how long I should wait between stages? Is a few days long enough to allow the specimens to adjust before increasing the concentration again?

I haven’t been able to find anything in the literature on this. Any advice greatly appreciated!

Best wishes, Robyn

Dr Robyn Cumming
Collection Manager, Marine

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