[Nhcoll-l] Answering a question about isopropanol storage

Sun Jun 12 22:09:44 EDT 2016

Brian,
This question comes up fairly regularly--often enough that I have saved the
following response to the question of ethanol vs. isopropyl. Please feel
free to ask if you have any further questions:

I get this question often. The short answer is, ethanol is a better
long-term preservative than isopropyl because ethanol is less toxic
(isopropyl is twice as toxic as ethanol, due to its faster permeation
rate), ethanol causes less shrinkage of specimens, less fading of patterns
and colors,  and fewer user health issues (many people, myself included,
get headaches from isopropyl fumes). However, this does not necessarily
mean that a collection that is already in isopropyl should be changed to
ethanol, as the change can create other issues.

Some people, particularly a few ichthyologists, insist that isopropyl is
equal to or superior as a preservative, but in my opinion the information
in the literature does not support their position. I have a full discussion
of the pros and cons of isopropyl (with full references to the literature)
in my book, *Fluid Preservation: A Comprehensive Reference* (2014). Here is
a very brief summary:  Isopropyl is a secondary alcohol, which means it
dissolves lipids better than ethanol (lipid extraction is a problem with
almost all preservatives, but is worse with isopropyl); as a secondary
alcohol, isopropyl is more reactive with oxygen and forms ketones and
unstable peroxides that can damage preserved specimens, which probably
accounts for the greater loss of pigments. Isopropyl causes greater
specimen shrinkage, can be difficult to mix thoroughly, may form
concentration layers in tall containers, and has been reported to soften
bone. One reason some ichthyologists prefer isopropyl is because specimens
preserved in it are more flexible than those preserved in ethanol, however,
the greater flexibility is because the tissue matrix undergoes more
breakdown in isopropyl than in ethanol. But back to your question--should
specimens in isopropyl be switched to ethanol? There is no clear and easy
answer. Specimens in isopropyl have already undergone shrinkage, so
switching to ethanol will not help that situation, although it may prevent
a little long-term fading. From a human health perspective, ethanol is
safer to work with, but there will be traces of isopropyl for decades to
come in the ethanol after the switch. The change would be
resource-consuming (time and money). Ideally, new specimens should be
preserved in ethanol and the old ones left in isopropyl, but this would
require some sort of container labeling so the two are not mixed up. So it
all depends on what your priorities are.

The Canadian Museum of Nature is one of the few collections to report on
what happens when specimens (fish, in this case) were initially preserved
in ethanol, then switched to isopropyl, and then back to ethanol, so you
might want to read their paper:  Laframboise, S., R.M. Rankin, and M.M.L.
Steigerwald. 1993. Managing change: alcohol transfer at the Canadian Museum
of Nature. Pp. 28-33 in Snyder, A.M. (editor). *The 1992 American Society
of Ichthyologists and Herpetologists Workshop on Collections Care and
Management Issues*, 52 pp.

John E. Simmons
Museologica
128 E. Burnside Street
Bellefonte, Pennsylvania 16823-2010
simmons.johne at gmail.com
303-681-5708
www.museologica.com
and
Adjunct Curator of Collections
Earth and Mineral Science Museum & Art Gallery
Penn State University
University Park, Pennsylvania
and
Instructor, Museum Studies
School of Library and Information Science
Kent State University

On Fri, Jun 10, 2016 at 2:04 PM, Sidlauskas, Brian <
Brian.Sidlauskas at oregonstate.edu> wrote:

> Hi folks,
>
>
>
> Yesterday I received a private question about why the Oregon State
> Ichthyology Collection is mostly stored in 50% isopropanol rather than 70%
> ethanol.  I get this question frequently, usually with some combination of
> dismay for the collection specimens and sympathy for me as their manager.
>
>
>
> The basic answer involves historical contingency.  I inherited a 20,000
> lot cataloged collection in isopropanol (plus a lot more in backlog), and
> wasn’t about to change out 20,000+ liters of fluid. Nor do I have the funds
> to do.
>
>
>
> The reasons that Carl Bond chose isopropanol in the first place (circa
> 1950) aren’t entirely clear to me, but my three best guesses are:
>
>
>
> 1)       50% isopropanol is slightly less flammable than 70% ethanol
> (slightly higher flashpoint, so perhaps better safety)
>
>
>
> 2)       Isopropanol is (or was) less expensive, particularly because the
> stock solutions involve more water.
>
>
>
> 3)       No one is tempted to drink the lab stocks of isopropanol
>
>
>
> All that said, there’s definitely a sense that isopropyl alcohol is less
> than ideal for long term preservation. When I tried to follow that to a
> source a while back, I couldn’t find anything very detailed about what
> those drawbacks were.
>
>
>
> I can certainly say that the specimens here at OSU generally look great.
> I’ve been posting photos recently on the collection’s Facebook page (
> https://urldefense.proofpoint.com/v2/url?u=https-3A__www.facebook.com_OregonIchthyologyCollection&d=AwIFaQ&c=-dg2m7zWuuDZ0MUcV7Sdqw&r=CLFZJ3fvGSmDp7xK1dNZfh6uGV_h-8NVlo3fXNoRNzI&m=2CnusiGBumMVXgNtNoRMdjcY5Y-p-VyoKfXwYQx4aFw&s=EAES6G0T8EfiN53NJyxVKF8XLYkaN4D0kXIEQIhdisA&e= )
> <https://urldefense.proofpoint.com/v2/url?u=https-3A__www.facebook.com_OregonIchthyologyCollection-29&d=AwMGaQ&c=-dg2m7zWuuDZ0MUcV7Sdqw&r=CLFZJ3fvGSmDp7xK1dNZfh6uGV_h-8NVlo3fXNoRNzI&m=dJo2jLcsWcYEYDAw5hIx5-keoCRISJ9nMwm_Xh3EQrU&s=0_88_eFhFM11IFP9_-xoVOwDi3EeEJC9ZaYLRDCBCbw&e=>
> to help promote an online fish systematics course that I’m developing, if
> anyone want to take a look.  There are also a bunch up at the collection’s
> database at https://urldefense.proofpoint.com/v2/url?u=http-3A__ichthyology.oregonstate.edu&d=AwIFaQ&c=-dg2m7zWuuDZ0MUcV7Sdqw&r=CLFZJ3fvGSmDp7xK1dNZfh6uGV_h-8NVlo3fXNoRNzI&m=2CnusiGBumMVXgNtNoRMdjcY5Y-p-VyoKfXwYQx4aFw&s=2gAKICbnPwHgKYNKKm0knlK6MsAIRnmMmbhVlWPvNsY&e= 
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__ichthyology.oregonstate.edu&d=AwMGaQ&c=-dg2m7zWuuDZ0MUcV7Sdqw&r=CLFZJ3fvGSmDp7xK1dNZfh6uGV_h-8NVlo3fXNoRNzI&m=dJo2jLcsWcYEYDAw5hIx5-keoCRISJ9nMwm_Xh3EQrU&s=1f1Pyb1AX11PAF15Las-XYQW3LsZ-kTx8vZa4-C_aNs&e=>
> .
>
>
>
> And, we just published this paper suggesting that fish specimen shape is
> stable over decades of isopropanol storage.
>
>
>
> https://urldefense.proofpoint.com/v2/url?u=http-3A__www.bioone.org_doi_abs_10.1643_CG-2D15-2D303&d=AwIFaQ&c=-dg2m7zWuuDZ0MUcV7Sdqw&r=CLFZJ3fvGSmDp7xK1dNZfh6uGV_h-8NVlo3fXNoRNzI&m=2CnusiGBumMVXgNtNoRMdjcY5Y-p-VyoKfXwYQx4aFw&s=hjHfhhi-6gX_X2VpRsZwQb14XEx-QeS8shAzTzC4CaQ&e= 
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.bioone.org_doi_abs_10.1643_CG-2D15-2D303&d=AwMGaQ&c=-dg2m7zWuuDZ0MUcV7Sdqw&r=CLFZJ3fvGSmDp7xK1dNZfh6uGV_h-8NVlo3fXNoRNzI&m=dJo2jLcsWcYEYDAw5hIx5-keoCRISJ9nMwm_Xh3EQrU&s=0esFdfGbfJcHNMO0tSarf5Px7YjOIt7KtyHt-mwtym8&e=>
>
>
>
> So, I’d be very interested to hear about whether there’s actually good
> data suggesting that isopropanol storage is seriously problematic!
>
>
>
> Thanks for reading, and best fishes,
>
>
>
> Brian
>
>
>
>
>
> --
>
> Brian Sidlauskas
>
> Associate Professor and Curator of Fishes
>
> Department of Fisheries and Wildlife
>
> Oregon State University
>
> 104 Nash Hall
>
> Corvallis, OR 97331
>
>
>
> brian.sidlauskas at oregonstate.edu
>
> 541-737-6789 (office) 541-224-3850 (cell)
>
> https://urldefense.proofpoint.com/v2/url?u=http-3A__ichthyology.oregonstate.edu&d=AwIFaQ&c=-dg2m7zWuuDZ0MUcV7Sdqw&r=CLFZJ3fvGSmDp7xK1dNZfh6uGV_h-8NVlo3fXNoRNzI&m=2CnusiGBumMVXgNtNoRMdjcY5Y-p-VyoKfXwYQx4aFw&s=2gAKICbnPwHgKYNKKm0knlK6MsAIRnmMmbhVlWPvNsY&e= 
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>
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