Manual vs. Automated LN2 Storage – Workflow & Temperature Comparisons
May 26, 2016
The International Society of Biobanking and Biorepository Annual Conference (ISBER) was held in April in Berlin, Germany. We conducted some new experiments and published a new poster at ISBER that compared typical workflow, time and temperature of manual vs. automated LN2 storage.
The Manual workflow, as you would expect, included racks pulled out by hand into the air. For the automated system we used the BioStore III Cryo storage system.
A summary of the results follows:
As one would expect with any automation, the user steps are greatly reduced and any time you can reduce manual intervention you will reduce the risk of human errors. Also ergonomics and user safety were improved.
On the temperature side, the results were interesting. Keep in mind that we previously found that convection was the primary source of innocent sample warming. Because of these findings, the BioStore III Cryo was designed to pull racks into an insulated sleeve. Our test data showed a 70% reduction in innocent sample warming during the first 30 seconds of exposure using the BioStore III Cryo vs. Manual.
With both Manual and BioStore III Cryo workflows, the top box innocent sample warmed the quickest. During the first 30 seconds of manual workflow a vial in the top box warmed at about 20°C/min, whereas in the BioStore III Cryo workflow it was near 7°C/min. Keep in mind that shelf height, sample volume, vial location and the presence of surrounding vials all affect the rate of warming. There is no one rate-of-warming for all situations.
Furthermore, a common manual workflow practice is to leave the rack out of the LN2 freezer while picking vials. Testing this workflow we found the top box innocent sample in a manually lifted rack to cross Tg (-135°C) in approximately 2 mins, whereas with the BioStore III Cryo it takes over 4 mins. Again, keep in mind that samples continue to warm after returned to the freezer, so if you returned your samples before 2 mins at -140°C they would warm far above Tg during the next few minutes of being back inside the freezer.