QC OF PORTABLE LN2 DEWAR

[NMATTEU]

LOOKING FOR METHOD TO QC TEMPERATURE OF PORTABLE LN2 DEWAR. NEED TEMP READINGS TO QUALIFY DEWAR AS PATENT, i.e. HOLDS TEMPERATURE OVER REQUIRED TIME INTERVAL (DAYS)

[Bonni Hazelton]

You can use a number of methods to verify the holding temperature of the LN2 dryshippers.

1-If you have a monitor with a thermocouple for temperatures as low as

-120 degrees C (the temp you will need to maintain in transit) and associated printer you can use it to record the temperature of the charged shipper every 4 hours. The length of time it takes for the temp to go above the -120 degree C mark, becomes your "holding time". For shipping, that time should be decreased by at least 24 hours for safety (we decrease by 48 hours to leave time for redirection of mis-shipped specimens!)

2-If you do not have the above equipment, CryoGuard M120 (Controlled Chemicals Inc.) temperature monitor can be used in somewhat the same fashion. This would require manual monitoring and recording and would also necessitate the opening of the shipper. Check the status of the monitor at set intervals (eg 4 hrs) and document (green= still below -120/red above -120).

Using the same criteria as above, set your "holding time".

3-The weight of the shipper can also be used to monitor holding time by measuring the weight of the shipper at each step in procedure #2.

First, weigh the completely empty chamber prior to charging. Weigh the chamber at the start of the procedure (full) and at each subsequent time point.

What you should see is that as long as their is nitrogen in the shipper (wieght is > empty weight) the temperature will hold. After validating and documenting this you can use the weight of the shipper not only to verify the holding time but also to ensure proper temperature at the receiving end (eg weight at time of receipt).

With all the verifications of holding time, do them routinely as when the shippers get "bounced around" during transport the vacuum can be lost very rapidly. You would probably notice changes during charging if there is a problem.