[Nhcoll-l] Answering a question about isopropanol storage

Sun Jun 12 22:27:53 EDT 2016

Thank you for sharing this John!

________________________________
From: nhcoll-l-bounces at mailman.yale.edu <nhcoll-l-bounces at mailman.yale.edu> on behalf of John E Simmons <simmons.johne at gmail.com>
Sent: Sunday, June 12, 2016 10:09 PM
To: Sidlauskas, Brian
Cc: nhcoll-l at mailman.yale.edu
Subject: Re: [Nhcoll-l] Answering a question about isopropanol storage

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
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On Fri, Jun 10, 2016 at 2:04 PM, Sidlauskas, Brian <Brian.Sidlauskas at oregonstate.edu<mailto: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=AwIGaQ&c=-dg2m7zWuuDZ0MUcV7Sdqw&r=CLFZJ3fvGSmDp7xK1dNZfh6uGV_h-8NVlo3fXNoRNzI&m=mUXFU-TPuXgFgPS9i-sjfik9mkbpeIJUtbhiqqeYVR0&s=AHxuKWHv-JVA_ql0AS8bXBpzQRMer6FL5iyPlW7bSVU&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=AwIGaQ&c=-dg2m7zWuuDZ0MUcV7Sdqw&r=CLFZJ3fvGSmDp7xK1dNZfh6uGV_h-8NVlo3fXNoRNzI&m=mUXFU-TPuXgFgPS9i-sjfik9mkbpeIJUtbhiqqeYVR0&s=3a4Wer3a0V8eTe8QM_Mi6nrUHCcH-q1rhAd6DihFDF0&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=AwIGaQ&c=-dg2m7zWuuDZ0MUcV7Sdqw&r=CLFZJ3fvGSmDp7xK1dNZfh6uGV_h-8NVlo3fXNoRNzI&m=mUXFU-TPuXgFgPS9i-sjfik9mkbpeIJUtbhiqqeYVR0&s=GbvxC3SDwvJ_Y5i3QqWfYLe7z0q1Gp-gEoMhPgOC4Uo&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

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