Utilising liquid nitrogen to preserve the viability of living cells and other organisms was established in the 1950’s and has been used over the decades to enable the safe storage of materials such as Human and Animal tissue, microbiology cultures and more recently T-cells for CAR T-cell therapy. For long term storage liquid nitrogen with a boiling temperature of 77.2 K (-196°c) is recognised as the safest temperature because it is -68°c below the glass transition temperature (Tg) of water (-132°c).

Samples can be stored within many types of containers, such as cryogenic vials (ampoules), straws, or bags. It is important to use a suitable container when storing in the liquid phase of a cryogenic vessel to ensure the closure of the container is near to 100% leak proof as possible. Liquid nitrogen ingress into the sample container can cause a rapid expansion of the liquid to gas when removing the container from the liquid storage, with the possible result of a health risk to the user or samples being lost.

Canisters inside storage vessel

Having established the appropriate sample container you can now look at which cryogenic vessel is best for you. Small volumes (up to 1,500 x 2ml vials or 3,500 x 0.5cc straws) can be held in canisters within the storage vessels, these would typically be stored within the liquid phase. Canister type storage vessels are available in various sizes and can be selected for maximum volume or for low evaporation rates of LN2 which if you do not want to fill the vessel so often. The higher volume vessels typically have larger diameter canisters which means the neck opening of the vessel is wider resulting in a higher evaporation rate. For larger vial quantities (up to 6,000) square boxes held in racks can be used. The material used for the canister rods is carefully selected to ensure minimal heat transfer from the outside of the vessel to your liquid nitrogen reservoir. These vessels can be fitted with temperature or low-level alarms to ensure the integrity of your samples. Vapour storage is possible by only partially filling the vessels so that your samples are suspended above the liquid however the liquid level needs to be monitored carefully as your safely margins will be reduced. These storage vessels are the XTL, HCL and LS range shown on our website.

Narrow neck vessel

For larger sample storage quantities, you need to make a decision as to whether your samples should be stored in the vapour or liquid phase. As previously discussed, sample closure integrity is an area of concern with liquid storage not just due to liquid nitrogen ingress into the container but also because of the risk of cross contamination from sample to sample.  When selecting to store your valuable product in the vapour space of a liquid nitrogen vessel you will reduce the amount of liquid nitrogen available as your energy source to keep your samples under the correct temperature conditions. To compensate the risk to your samples narrow neck vessels are available which dramatically reduces the liquid nitrogen consumption and therefore increases your safety margins and avoids constant filling. By design these vessels, by design allow for as close to cryogenic temperatures (-190°c) at the highest point of your sample area. Vapour storage in conventional wide neck vessels is obtainable by adding a vapour phase platform in the bottom of

Wide opening vessel

the vessel which lifts the samples out of the liquid. These may offer easier access however the increased evaporation of the liquid nitrogen needs to be considered for the safety of your samples. Vapour storage vessels are the LABS series with conventional wide storage offered in the K Series.