[Nhcoll-l] Answering a question about isopropanol storage

[Sidlauskas, Brian]

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=dJo2jLcsWcYEYDAw5hIx5-keoCRISJ9nMwm_Xh3EQrU&s=q6zvUEehcR5ufI4tBasH_JE4CZ7zwvfOjEhtrTAtrlM&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=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=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<mailto:brian.sidlauskas at oregonstate.edu>
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