Internally threaded CryoTube Vials are designed for vapor phase liquid nitrogen freezing. The cap incorporates a silicone gasket to enhance sealing properties. Externally threaded CryoTube Vials are designed for mechanical freezing. The external screw cap reduces risk of contamination due to handling.
The CryoTube Vial of choice for liquid N2 immersion is the internally threaded design, incorporating a silicone gasket. At ultra low temperatures, any sealing material becomes inflexible. A theoretical risk of leakage is present when any mechanical closure is used. To facilitate leakproof storage, mechanically closed containers must be hermetically sealed in a protective envelope. The Nunc CryoSystem includes CryoFlex Tubing, a heat sealable polyethylene tubing designed for CryoTube Vial encasement. The use of CryoTube vials for freezing in liquid nitrogen (liquid phase) storage without CryoFlex Tubing poses a safety hazard.
Warning: Do not use NUNC CryoTube Vials in liquid phase of liquid nitrogen unless correctly sealed in NUNC CryoFlex Tubing, LS-2000 (343958). Improper use may cause entrapment of liquefied nitrogen inside the vial and lead to pressure build-up, resulting in possible explosion or biohazard release. Use appropriate safety procedures as outlined in the Nalge Nunc International Cryopreservation Manual when handling and disposing of the vials.
Wear appropriate protective clothing including gloves, face guard, etc., during all transfer processes.
The CryoTube Vials should be stored at least 24 hours in the gas phase of the liquid nitrogen freezer. This should allow trapped liquid nitrogen to evaporate and escape slowly, thereby reducing the possible pressure in the CryoTube Vial. After at least 24 hour storage in the gas phase, the CryoTube Vials may be put into a water bath and covered with a towel. After thawing, tube contents can be transferred.