Cryogenic vials...really necessary?

Peter pxpst2 at vms.cis.pitt.delet.edu
Wed Oct 8 17:34:01 EST 1997


In article
<Pine.SOL.3.96.971008155727.25806A-100000 at ascc.artsci.wustl.edu>, Alex
Brands <abbrands at artsci.wustl.edu> wrote:
> I've been keeping my glycerol stocks in 2ml snap-cap eppendorf type tubes.
> Today, someone told me that glycerol stocks will eventually dessicate in
> those types of tubes, and that's why the screw-cap cryogenic tubes are
> sold.
> 
> So, can anyone confirm or deny that the snap-cap tubes are inappropriate
> for long term frozen storage?  If they are, roughly how long the stocks
> will last in a snap-cap tube?

Depends on how long you plan to store them and what you will store them in.  
The drawback to snap caps is firstly contaimination.  Snap cap seals are
not 100% airtight.   And with the way they(the snap cap tubes) will be
opened and closed, one will greatly increase the chance of
contaimination.  Obviously, if they are bacterial cells and can be grown
under selection this is not that big of a deal but for eukaryotic cells
this is a big problem.
As I said earlier the snap caps are not air tight so exchange of air
between the inside and outside does occur, and since the outside air is
very dry(air at -20C does not have the capability of holding moisture in a
liquid state) the moisture will be drawn out of the tubes.  Remember back
to general chemistry the princible of sublimation(  WATER(solid)------>
WATER(gas) skips the liquid pase altogether).  It is what drives the water
out of the tube and onto the ice sheet in the freezer on the condensor. 
Since you have glycerol this process will be greatly impeeded due to the
lowering of the water Vapor pressure.
Storage time for bacteria in this manner would probably be no more than 9
months to a year and assuming that you put a secondary seal of parafilm
around the top.
As for Nitrogen storage, SNAP CAPS ARE A REAL BAD IDEA AND CRYOTUBES
SHOULD ALWAYS BE USED.  Snap caps will fail.


Hope this helps
Peter



More information about the Methods mailing list