To fit different vessels into one bucket (for swing-out rotors) and ensure that a wide variety of tubes can be accommodated, it is often necessary to use an adapter designed for the specific vessel. These adapters are inserted into the bucket.
Most centrifuge manufacturers differentiate between one-piece and modular adapters. A modular adapter consists of several layers that are stacked. This has the advantage that the user can simply remove layers of the adapter to adjust it to different vessel lengths.
Why is an adapter necessary?
Let’s say you want to use a swing-out rotor and 50 mL conical tubes. The bucket cannot hold the tubes without an adapter (in contrast to fixed-angle rotors with boreholes, such as those dedicated to 50 mL conical tubes). Usually, centrifuge manufacturers offer a huge number of adapters for all kinds of vessels, so it can become a challenge to find the correct one for your tube!
First, it is important to use original adapters from the manufacturer of the rotor and centrifuge. Manufacturers test their adapters for centrifugation stability and safety at the end of the adapter development process, so the customer can always be sure that this adapter/rotor/centrifuge combination is safe. Trying to fit adapters from other manufacturers or even “do-it-yourself” adapters in a rotor can lead to all kinds of problems – from imbalance, a non-correct swing-out of the bucket, or even a rotor crash.
When looking for the correct adapter for your tube, there are a few things to keep in mind:
- The adapter should always cover at least 2/3 of the tube length to provide optimal support during the centrifugation run.
- On the other hand, the adapter should not be longer than the tube length, because in that case the tube will only “hang in there” instead of touching the bottom of the adapter. This can lead to the breakage of the tube lid or the tube itself, or the tube may “disappear” inside the adapter and be difficult to remove without mixing its contents.
- The adapter should support the vessel bottom. Therefore, you can find adapters for conical tubes, skirted conical tubes, round-bottom or flat-bottom tubes, etc.
- Once you have the correct information about the tube diameter, length and bottom shape, it is easy to find the right adapter. If there is no perfect match, look for the closest diameter possible, since the tube walls should be supported by the adapter like a hand in a glove (if the glove is too big, it won’t keep your hands warm or fit securely).
- Do not squeeze or push vessels into non-fitting adapters. The forces exerted on the tube during the run can lead to tube deformation, with the possibilities that the tubes cannot be removed from the adapter after the run (if the adapter was too narrow) or break (if the bottom shape was not correct, e.g. a round-bottom tube in a conically shaped adapter).
- Since an adapter can change the rmax, make sure the adapter will not prevent your reaching the required g-force.
- If you are in doubt, contact your centrifuge manufacturer or consult the operating manual.