Microcentrifuge tubes/cap bursting - (Aug/29/2013 )
I have had a problem, along with others in my lab, in which we snap freeze tissue samples in liquid nitrogen. When the tubes are removed before placing in a -80 degree C freezer, some tube caps burst off. . I have never had this problem before until recently. My guess is that some caps may not have a strong enough seal which is causing a small amount of N2 to enter the tube and then evaporate as the tube warms (causing it to expand and burst). But again I have never had a problem with this before. Does any one have suggestions to prevent this from occurring.
Mike
you could either change to locking (or sealing) tubes or try cap locks like these from usa scientific or similar.
As far as I know no tube can stay completely sealed when entered in LN, not even cryogenic tubes. Some girl in our lab use cryotubes like these for freeze-thaw cells for protein extraction using LN and I never heard about any problem.
These tubes sometimes even have an O-ring for better sealing. If you still have problems let them warm up a bit in the gas phase.
As you are going into the -80 you could snap-freeze in a dry ice/methanol (or isopropanol) bath, if you don't have dry ice, just place a container of methanol/IPA in the -80 to pre-cool, then use it.
El Crazy Xabi on Fri Aug 30 00:39:25 2013 said:
As far as I know no tube can stay completely sealed when entered in LN, not even cryogenic tubes. Some girl in our lab use cryotubes like these for freeze-thaw cells for protein extraction using LN and I never heard about any problem.
These tubes sometimes even have an O-ring for better sealing. If you still have problems let them warm up a bit in the gas phase.
I second these tubes. They are not rated for liquid phase but I have successfully used them. I prefer storage in the gas phase in which they have been flawless.
I've had similar "explosive" problems like this before and I solved them by snap freezing my samples in an upward position. Basically I put a standard tube rack in a cooler, pour liquid nitrogen until it fills the whole bottom and enter the slots of the racks (wait for temperature to stabilize, otherwise the bubbling nitrogen will make holding the tubes in the rack impossible). Then I just collect my sample on a labelled tube and snap freeze it by placing it in the rack. If you have many samples, just remember of refilling the N2 a little bit from time to time...
If liquid LN2 leaks into the screw top vials, and they are then removed from liquid, they can explode. This is the reason for the use of vapor phase cooling. If you do this, be very careful!