[Nhcoll-l] Freezer storage of EtoH tissue samples

Mon Feb 2 04:21:23 EST 2015

We store majority of samples in a -25°C deep freezing chamber, 200 x 2 
ml tubes per rack, several ten thousand tubes are currently stored per 
chamber. Apparently we do not have this strict safety regulations for 
our -25°C storage; these do apply only for room temperature storage at 
the moment (where were are allowed to have no more than 20 L of 96 % 
Ethanol in a fireproof canister inside our alcohol collection) and 
inside the lab facilities (histology & DNA lab), where we were advised 
recently that we need to adjust & re-equip fridges and cupboards used 
for storage of chemicals. The only distinction here is that fluids and 
especially acids and bases must be stored separately from solids, and 
that storage of highly reactive peroxides would need special 
consideration (but we don't use such highly self-reactive peroxides).

It might be worth to check the flash point pure ethanol at -25°C; 
freezing point for 96% is between -73/-110 (°C/F) and -115/-175 (°C/F), 
so keeping ethanol tubes at -80°C means (depending on dilution of 
ethanol resulting from dehydrated cells / tissues) keeping tissues close 
to freezing point of the fluid (but exposing samples to physical damage 
resulting from formation of ice crystals).

Flash point at -25°C should be well below 16°C, and also evaporation 
pressure inside tubes (and thus building of highly combustible 
ethanol-air mixtures) is considerably lower. It might perhaps be worth 
checking this with colleagues from Chemistry departments at University. 
I doubt that a spark released at the inside of a freezer (which could 
either be released from the lamp or the control) could ignite the 
content of a tube. More likely in case of failure (of the compressor) 
would be that the insulation catches fire. Perhaps a physical test 
witnessed by the fire marshal helps: try to ignite a 2 ml ethanol tube 
at room temperature under controlled conditions, place a box with more 
ethanol tubes in close vicinity and see what happens. I seriously doubt 
that these would catch fire, too. But the devil is a squirrel and this 
is not a question about good judgement  but rather an administrative one 
which helps to demonstrate power ...

Hope this helps,
all the best
Dirk

Am 30.01.2015 um 19:24 schrieb John P. Sullivan:
> I am curious to know how people on this list deal with cold storage 
> for DNA samples in ethanol.
>
> We have thousands of tissue samples and fish fin clips preserved in 
> 95% EtOH in 2ml Sarstedt screw cap vials. We typically store 16 boxes 
> of 81 tubes per freezer rack and can fit 20 racks in a 
> refrigerator/freezer.  This makes for a maximum of 52 liters or 13.7 
> gallons of EtOH stored in such a refrigerator/freezer.
>
> We have been informed by Environmental Health and Safety at our 
> institution that it is improper to store these in regular freezers (as 
> opposed to prohibitively expensive, specialized “flammable material” 
> freezers).
>
> This person cited NFPA 45  10.5.2 and 12.2.2 and Article 501 of code 
> 70 the National Electrical code.
>
> Here are links to EH&S pages at several institutions that seem to 
> indicate ethanol storage requires flammable material freezers:
>
> https://urldefense.proofpoint.com/v2/url?u=http-3A__www.usd.edu_research_research-2Dand-2Dsponsored-2Dprograms_upload_Flammable-2DLiquids-2DStorage.pdf&d=AwID-g&c=-dg2m7zWuuDZ0MUcV7Sdqw&r=CLFZJ3fvGSmDp7xK1dNZfh6uGV_h-8NVlo3fXNoRNzI&m=EQOvb7tfOYP7DFTGQe7aTcg8IbeMrUIFY3w22ylp7Jo&s=hcca_EI9_YzWlS358en6nvshcyH3f5JbaP_c1wUZc_o&e=  
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>
> However, my informal polling of colleagues on Facebook suggests that 
> many of them do in fact store screw-top tubes with tissue samples in 
> ethanol in regular freezers (though perhaps without the 
> approval/oversight of their EH&S departments). My view is that 
> fire/explosion risk from storage of these vials must be negligible to 
> non-existent.  The flashpoint of pure EtoH is 16.6°C.  This temp would 
> only be reached if a freezer failed and no action was taken for a long 
> period of time. The risk of EtOH vapors concentrating in any quantity 
> near internal mechanisms that could spark are minimal since tubes are 
> sealed.
>
> My questions are:  Has anyone here received explicit clearance from 
> their EH&S to store EtOH tissue samples in regular freezers?  If you 
> got this, what was required to obtain it?  If you have 
> ethanol-preserved tissue samples, how do you store them?
>
> This could make for an interesting and useful conversation, but feel 
> free to contact me off-list if you’re concerned about being “on the 
> record.”
>
> - John Sullivan
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> John P. Sullivan, PhD
>
> Collections Archivist & Curatorial Affiliate - Cornell University 
> Museum of Vertebrates
> Research Associate - The Academy of Natural Sciences of Drexel University
>
> Cornell University Museum of Vertebrates
> 159 Sapsucker Woods Road
> Ithaca, New York 14850-1923 USA
>
> jpsullivan at cornell.edu <mailto:jpsullivan at cornell.edu> / office 
> 607.254.6237, cell 607.342.2234, fax 607.254.2415
>
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