Snap Freezing With Dry Ice or Liquid Nitrogen


Snap freezing is the technique in which a sample is rapidly frozen using dry ice, a dry ice/ethanol slurry or liquid nitrogen.  Samples frozen in this manner include bacteria and viral stocks, cell lysates, proteins, and tissues.  Snap freezing reduces the chance of water present in the sample forming ice crystals during the freezing process, and better maintains the integrity of the sample.  In the case of tissue or lysates, snap freezing slows the actions of proteases and nucleases to inhibit degradation of molecules such as RNA or proteins.

Typically, snap freezing is performed either directly in dry ice or in a bath containing dry ice with ethanol or isopropanol.  Liquid nitrogen is commonly used for snap freezing tissue pieces.  BioCision tools including CoolRack, CoolBox and ice buckets, are easily adapted to these techniques and eliminate alcohol from the process, providing easier handling, organization and better reproducibility.

Snap freezing in dry ice
Current method of snap-freezing samples in dry ice. The random layout can result in misidentification and errors in processing, and non-uniform dry ice contact can result in freezing variability.

Snap freezing in dry ice using a CoolRack

CoolRack tube modules rapidly adapt to the dry ice temperature (-78ºC in approximately 6-7 minutes from room temperature), allowing you to snap freeze your samples in the CoolRack module without direct contact with dry ice.  Samples stay organized and freeze upright and uniformly.


CoolRack thermo-conductive sample modules can also be used in liquid nitrogen.* After approximately 15 minutes, a room temperature CoolRack module will equilibrate to approximately -140ºC and remain there while surrounded by LN2. Freezing tubes in a CoolRack keeps all tubes upright and organized, and provides uniform effortless freezing at ultra-low temperature.




Use of CoolRack Module in Snap Freezing Increases Reproducibility



Performance test: Tests were performed with a 0.5 ml Sarstedt tube (#72.785)containing 0.25 ml water.  The interior water temperature was measured using a thermocouple probe inserted through a hole introduced into the cap and held in an axial orientation by a custom cap adaptor. Vials were placed in a dry well in the CoolRack (green) or directly into dry ice (red) and the temperature recorded. Data shown are from three different vials.




Type of Tube

CoolRack (# of samples)

CoolRack Catalog #

Ice Pan

Microfuge tubes

1.5 or 2.0 mL

CoolRack M6 (6)

CoolRack M15 (15)

CoolRack M30 (30)

CoolRack M90 (90)

CoolRack M96 (96)






1L Mini Ice Pan

1L Mini ice Pan

4L Midi Ice Pan

9L Maxi Ice Pan

9L Maxi Ice Pan

Cryogenic vials

CoolRack CF15 (15)

CoolRack CFT30 (30)

CoolRack CF45 (45)




1L Mini Ice Pan

4L Midi Ice Pan

4L Midi Ice Pan

Centrifuge tubes

CoolRack 15ml (9)

CoolRack 50ml (4)



4L Midi Ice Pan

4L Midi Ice Pan

*It is important to adhere to laboratory safety protocols when handling dry ice or liquid nitrogen. CoolRack modules can cause skin burns when cooled to ultra-low dry ice or LN2 temperatures.  Use extreme caution and protective clothing and equipment when handling CoolRack modules in dry ice or LN2.

Application Note:
Click herefor a printable version of this application
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Quick Protocol:

Snap Freezing with CoolRack
1)  Place pelleted or crushed dry ice in your ice pan
2)  Place CoolRack module of choice on top of the dry ice for 5-7 minutes to equilibrate to temperature of dry ice
3)  Place your samples in CoolRack module and wait 3-4 minutes
Depending upon your sample, freezing can be complete within 3-4 minutes, but we suggest waiting for the full ten minutes before transferring to a -80°C freezer or liquid nitrogen.



Snap Freezing in Dry Ice Using a CoolRack Module >

Snap Freezing of Tissue Samples >

Bacteria Cryopreservation using a CoolRack Module >
Virus Cryopreservation using a CoolRack Module >



Learn more about:

CoolRack thermo-conductive tube

Ice pans and buckets
made from non-toxic EVA foam

TruCool leak-proof cryogenic vials

vial grabbers to protect fingers from frozen vials >


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