Missing Housekeeping in Your Freezer?

21/11/18

Sorting of samples in the ULT freezer is often a lively discussion in lab teams. Freelance storage with single 50 mL conical tubes or microtubes in a plastic bag can create at least irritation in the lab team. Even piled freezer boxes are suboptimal if you store four piles in a row and six piles side-by-side.

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.

Type of racks
In general, there are two rack styles available to make your freezer usage the most efficient: Side access racks or drawer racks. So-called bins are subversions of drawer racks to store bags or similar non-standardized containers.

Side-access racks
The side-access rack is an open rack with access from the side. When using side access racks, accessing samples means removing a good portion of the side access rack completely removed from the ULT. During this process, most of the sample storage boxes are removed from the cold interior of the ULT freezer facing the warm environment.

Stainless steel side access rack

Racks for chest freezers are a sub-type of side-access racks, called tower racks. They can be equipped with locking rods to secure freezer boxes when pulling the rack out of the chest freezer.

Stainless steel rack for chest freezer

Drawer racks
A drawer rack contains a multiple of drawers. This type of racks works like a dresser where you pull-out that very drawer where you expect your object of interest. When using racks with drawers, only that relevant drawer with the freezer boxes of interest is pulled-out. All other freezer boxes, incl. all samples, safely stay in the cold interior of the ULT freezer. Drawer racks are mostly heavier but as most of the weight is not moved when pulling out the drawer-of-interest, this is less relevant.
Good-designed drawers should be engineered in a way to enable smooth movement at -80 °C for ergonomic handling.

Stainless steel drawer rack

Depth of rack - 4 or 5 boxes?
There are two rack size systems used in laboratories - the standard 4-boxes deep racks and 5-boxes deep racks. Why is this of any interest? In case of an emergency, you want to save your valuable samples. The easiest way is to take out all racks (with the samples/ boxes included) and store those racks in some backup freezer. To be compatible with most common ULT freezer suppliers, you should select an ULT with 4-boxes deep racks.

Stainless steel or aluminum
By standard, there are two types of rack materials available: Stainless steel is a very robust and stable material. This results in longevity and higher capacity. The higher weight of stainless steel can be counterbalanced by thinner sheets of the rack.
Aluminum as non-corrosive anodized metal is very light but less stable. The racks need more massive sheets to be stable enough.

Sample storage rack selection
Though you often only hear about the safety of your samples, the method of sample storage and organization can be just as important. To select the right set of racks for optimal usage of your freezer, we advise you to consider a few questions:

1. What type of freezer do you need to equip?
2. Do you prefer stainless steel or aluminum racks?
3. Do you need drawer or side access?
4. What type of vessels do you use?
5. How can you organize your freezer in an easy and logical way?