Centrifuge Rotor Choose And Maintain

Centrifugation is a laboratory technique separate the liquid mixture to single components. The centrifuge forces spinning sample at high velocity.

Due to balancing of samples the rotor received most wear.

The centrifuge rotor is an essential element of the device, which determines not only the sample size but also how the particles migrate and distribute in solution after centrifugation.

Some centrifuges come with more than one rotor, widening the scope of their applications,The other centrifuges, however, are sold with only one undetachable rotor

Swinging Bucket Rotor

Swinging Bucket Rotor

Swinging Bucket Rotor

Rotor Types

Depending on the application, the centrifugal forces generated in laboratory centrifuges can vary from a few hundred g up to 1 000 000 × g

For a wide range of routine applications, the standard benchtop and clinical centrifuges may present one of the following types of rotors (Ohlendieck & Harding, 2017):

Multiple Container Rotors

1. Swinging-bucket rotors

During centrifugation, the rotor buckets swing out in the same direction of the centrifugal force, elevating the sample up to 90º relative to the rotation axis

This type of rotor is mainly used for rate zonal centrifugation, i.e., to separate particles as a function of their size and density, in which the maximum resolution in particle separation is needed

Swinging-bucket rotors are also suitable for isopycnic centrifugation, i.e., separation based on density only.

Given that during centrifugation, tubes reach a 90ºC angle, the overall particle migration distance is higher than in fixed-angle rotors. As particles with small sizes migrate to the complete extension of the sample tube, the time to reach the tube bottom is higher than fixed-angle or vertical-tube rotors.

Advantages: Higher separation resolution; adaptable to different sample containers and volumes (e.g., plates, 15mL tubes, 50 mL tubes and bottles)

Disadvantages: Longer centrifugation times; lower number of tubes per run than fixed-angle rotors

swinging bucket rotor

2. Fixed-angle rotors

Available for purchase here. Tubes are held in a fixed position (usually 45º) relative to the rotational axis. Because of that, particles migrate in a downward spiral manner, and sediment in the bottom of the tube. Smaller rotor angles result in more diffuse sediment (pellet).

Fixed-angle rotors are suitable for the fractionation of samples in which the sedimentation rates of the different components differ significantly, such as the separation of cellular components like mitochondria, cell nuclei, and cytoplasmic content

Fixed-angle rotors usually accommodate a higher number of samples than swing-bucket rotors, which makes them more suitable for high throughput applications;

Because of the rigid design of the metal alloy material, fixed rotors can resist much higher gravitational forces, with minimum metal stress, which are used for the separation of biological macromolecules such as RNA, DNA, and protein.

3. Vertical rotors and near-vertical rotors

Tubes are held between 0º – 9º from the axis of rotation, which represents the shortest radial distance, and therefore the shortest pathlength for particles during centrifugation. In vertical and near-vertical rotors, particles sediment throughout the wall of the tube. Due to the shorter radial distance, centrifugation time is reduced, which may be important for certain biological samples.

low speed centrifuge rotor 5ml test tube

low speed centrifuge rotor 5ml test tube

high speed centrifuge rotor 

Continuous Flow (“hollow”) Rotors

1. Continuous-flow rotors

They are used to process large volumes of samples with high centrifugal forces, in a less time-consuming manner, as their use avoids start-and-stop to consecutively decant the supernatant. This type of rotor is used to recover large volumes of biological components such as viruses, mitochondria, bacteria, and algae.

Does not allow gradient centrifugation;

2. Zonal rotors

They are similar to continuous flow rotors but suitable for differential centrifugation, as they allow for density gradient solutions to be loaded prior to the target solution

Zonal rotors are used for large-scale zonal centrifugation, recovering the sample components as bands in a gradient.

3. Airfuge rotors

They are specially designed for pelleting small particles such as viruses and proteins. The rotor is supplied and driven by a pressurized air source. Rotor speed can be determined by the conversion of the applied air pressure to rotations per minute (rpm).

Importantly, the deceleration process is very slow to avoid a mixture of the sample components. Airfuge rotors are held in place by a pressure differential created by the applied centrifugation force, which makes these rotors extremely safe. Furthermore, in Airfuge centrifuges, a filter is supplied with the ultracentrifuge for water and oil removal from the air supply.

4. Analytical Ultracentrifuge (AUC) Rotors

Analytical ultracentrifugation combines high-speed centrifugation with optical detection systems to observe particle separation in real-time. Therefore, AUC rotors must allow light to reach the sample.

5. Elutriation rotors

They are designed to concentrate monodisperse solutions of single cells or particles, according to their size. Elutriation rotors combine centrifugal force and fluid velocity, two forces that affect particle migration. Centrifugal force drives articles away from the rotational axis, while fluid velocity drives them in the opposite direction – counterflow elutriation