Cryogenic vials...really necessary?

Martin Goodson bapn4 at central.susx.ac.uk
Thu Oct 9 07:14:39 EST 1997


Peter (pxpst2 at vms.cis.pitt.delet.edu) wrote:
: In article
: <Pine.SOL.3.96.971008155727.25806A-100000 at ascc.artsci.wustl.edu>, Alex
: Brands <abbrands at artsci.wustl.edu> wrote:
: > 
: > 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. 

I have a feeling that the reason that air in a freezer is so dry is that all
of the vapour condenses and freezes into ice. This ice does not then melt and 
evaporate because it is so cold. This as true for the ice in a glycerol
as it is for the ice sheet in the freezer. There is no reason why water
would be drawn out of a tube and onto the freezer wall since they are
both in the same environment (ie very cold).

martin



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