[Nhcoll-l] storage of 70% ethanol specimens at low temperatures for an extended period

Tue Nov 8 17:26:11 EST 2016

Dear Dirk

Thanks for your advice.  I am currently weighing up my options.  Perhaps the problems associated with storing the specimens at below 15°C are not worth the risk.  After all, as a collection manager it is my responsibility to store our material in the best conditions possible to ensure that it is available in good condition for future researchers.

Cheers

Al

From: nhcoll-l-bounces at mailman.yale.edu [mailto:nhcoll-l-bounces at mailman.yale.edu] On Behalf Of Dirk Neumann
Sent: Friday, 4 November 2016 7:20 PM
To: nhcoll-l at mailman.yale.edu
Subject: Re: [Nhcoll-l] storage of 70% ethanol specimens at low temperatures for an extended period

Hi Al,

you might see yourself confronted with the following problems:

fatty specimens: if you have specimens that are very fatty or include a lot of oils (e.g. some larger cyprinids or sharks), you may have problems with fatty deposits that build up on the specimens and which might be hard to remove afterwards (e.g. cholesterol, but also thin oil films on sharks). This can leads to acidic and highly reactive surface layers which may damage specimens, especially fish with their thin bony structures such as scales or in the head skeleton. Similar depositions can be observed in insects if these are stored refrigerated (e.g. in tissue collections at 4+°C or below) because of fats released from fat bodies. It is worth to consider to check each single drum after removing it from the cold storage period and to consider time and workforce to remove such deposits from specimens thereafter.

reactions inside the holding fluid: inside each jar, you have a complex chemical mixture (preservative, residual fixatives & body fluids that leach from specimens, denaturing agents, etc.). When lowering the temperature, you shift the equilibrium and some of these may start to fall out (this is the paraformaldehyde needles or "coudiness" you already mentioned). This might not be that much of a problem in your drums (because of the given fluid : specimen ratio), but it might be worth to check if after the cooler storage it is necessary to exchange the holding fluid. At this point, when you discover "Yes, I need to exchange it", you change also the stable equilibrium of preservative(s) and specimens inside your drums. This means that you may trigger a couple of deteriorating processes again (e.g. oxidisation because of O2 influx, leaching of body fluids, decolourisation, etc.). For some specimens this might be less critical, for others more. In any case you should clean the respective drums if specimens ought to go back in the same containers.

reactions of the holding containers: should be that critical with your plastic drums; in fact lower temperatures and thus shrinkage of the lids should increase tightness of the drums and decrease evaporation losses. However, I would avoid such experiments with glass containers, especially historic ones (such as old battery or ground stopper jars), as this could have potential to break the necks of such jars or the jar itself (because of the tension that builds up inside the glass melt on the one, and - for stopper jars - in the neck of the jars on the other). Might be worth to check the gaskets (shrinkage) after you have removed the drums from the cold storage again. Could happen that they do not expand to the original size again, so evaporation from these drums might increase (some sort of monitoring is surely advisable).

Condensation issues: when bringing your specimens in the cooler storage, you may have issues with condensation of water inside the container (depending on how often the material / storage area is accessed from the outside during this time. It shouldn't be that much of an issue for specimens inside the drum, but maybe for any labels / inscriptions on the outside of your drums (if this is the case).

Hope this gives you some guidance.

Have a nice weekend & all the best for the move of your fish collection!
Dirk

Am 04.11.2016 um 04:15 schrieb Alastair.Graham at csiro.au<mailto:Alastair.Graham at csiro.au>:
Hello all

Does anyone have any experience with storing preserved specimens at temperatures below 15°C (59°F) for an extended period?  Or, what is the lowest temperature that preserved specimens can be safely stored?

A portion of our fish collection needs to be re-located for 4-6 months (perhaps even longer) during building works.  Our specimens were originally fixed in 10% formalin and have been transferred to 70% ethanol for long-term storage.  The specimens are stored in 30 litre plastic drums (high density polyethylene), which have rubber gaskets.  I will be re-locating about 150 drums.  I had originally suggested hiring a hazardous materials shipping container with temperature control (15-22°C or 59-72°F).  However, such a container is proving difficult to source.  Now, a refrigerated shipping container has been suggested, although I do not know the temperature range it can be set at.

John Simmons in his Fluid Preservation - A Comprehensive Reference (2014) states on page 122 that the preferred storage environment for fluid collections is 18-21°C (65-70°F)".  Also on pages 103-104, John refers to a test where he placed jars of specimens in a refrigerator, demonstrating that the 70% ethanol turned cloudy below about 60°F (16°C).  "The cloudiness may have been caused by the formation of paraformaldehyde from the trace amounts of formaldehyde in the preservative, the congealing of lipids extracted by the alcohol, or other causes, but in any case, it was an unacceptable change in the preservative."

It has also been suggested that storing the specimens below 15°C and then moving them for examination to a lab at room temperature (22°C) could be harmful to the specimens.  Additionally, the humidity of the shipping container may promote mould growth on the drums.

Perhaps I have (or actually John in his book has) answered my question about what is the lowest temperature that specimens can be safely stored.  However, I would be interested to hear your views on storing specimens for an extended period below 15°C.

Cheers

Al

Alastair (Al) Graham
Fish Collection Manager
Australian National Fish Collection
National Research Collections Australia
CSIRO National Facilities and Collections

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