Ask the expert - Answer by Dr. Jan Bebermeier, Global Marketing Manager Cold Storage at Eppendorf
This article appeared first in “ Inside Cell Culture ”, the monthly newsletter for cell culture
The storage style of samples in the ULT freezer can result in a lively discussion in lab teams. Freelance storage with hundreds of single microtubes in a plastic bag or even spread in one ULT freezer compartment can end up in tough discussions within the lab team.
For optimal and economical usage of the existing storage room at -80°C, vessels should be stored in freezer boxes which fit exactly to the vessel dimensions. For sure, 2 mL vessels can be stored in boxes dedicated for 25 mL conical tubes. But this style is uneconomic as you waste a lot of storage space. Besides, removing microtubes out of the 70 mm deep boxes is quite uncomfortable. Nowadays, there are all kind of different box sizes available, fitting to all commonly used vessel types. Different inner grid variants provide a perfect fit to these formats: cryogenic tubes, microtubes, conical tubes 15 and 50 mL, and other laboratory vessels. Common size standard is “inch”, e.g. 2 in boxes for 53 mm microtubes. The footprint of the freezer boxes is by standard 133 mm x 133 mm. Metal racks
Related metal racks are standardized for these footprints. Make your scientific life easier: store your freezer storage boxes within organized freezer racks. These metal racks optimize your freezer space and make it easy to find the items you desire. Don’t waste time sifting through unsorted samples. Keep in mind, your other samples will defrost as well when the freezer door is open. Sorting of samples
At the beginning of a research life, the number of samples resp. vessels is limited. The approach “all protein samples belong to the first box, the DNA samples belong to the second box, ...” fits. Over the time, the accumulation of samples exceeds the capacity of this sorting style.
A sorting system based on metal racks provides a systematic approach. Sample management for easy refinding of samples can be handled by dedicated databases. Sample management software
based lists or even paper-based lists for sample management are a way to go as long as your stock of samples is limited. The more samples you have, the more you need a dedicated sample management software. This kind of software enables you to document and monitor your sample treasures. Besides the exact position within the freezer, the software also stored further background information about the sample.
Please benefit from free test trials to check out if the software fits to your needs before you decide, e.g. www.elabnext.com/eppendorf Person in charge
As freezers are quite often used and shared by different people and sometimes even by different teams, the feeling of responsibility is sometimes suboptimal. It is recommended to define one person per freezer who is in charge. Not in charge of cleaning up for everyone but to take care of the freezer as an instrument and define guidelines about storage and handling of all samples. Regular clean-up day once a year
Even with the best sample management system, freezers tend to fill up pretty soon. Before ordering a further, new freezer, you may check if all samples really need to be stored longterm. We recommend to perform a freezer-clean-up-day once a year to check which samples may be discarded (via autoclave).