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What is the difference between a fixed-angle and a swing-out rotor?

November 29,2023

In the world of centrifugation, the choice between a fixed-angle rotor and a swing-out rotor is a critical decision that can significantly impact experimental outcomes. Both rotor types serve distinct purposes, and understanding their differences is essential for optimizing centrifugation protocols in various laboratory applications.

Fixed-Angle Rotor:

A fixed-angle rotor, as the name suggests, holds tubes at a fixed angle relative to the axis of rotation. Common angles include 45 degrees and 90 degrees. This design results in the sedimentation of particles along the tube wall during centrifugation.

Fixed-angle rotors are the most common type of rotor. They are simple to design and manufacture, and they are relatively efficient. Fixed-angle rotors are often used in applications where precise control of the rotor's position is not required.


The isolation of biological macromolecules, including RNA, DNA, and proteins, demands a higher gravitational force compared to the pelleting of animal and plant cells. For instance, achieving the isolation of bacterial ribosomes may necessitate centrifugation at 100,000 x g. Consequently, fixed-angle rotors prove essential for ensuring the efficient sedimentation of these macromolecules.

Furthermore, due to the reduced time required for pelleting, any application that calls for the swift pelleting of a sample would be optimally served by a fixed-angle rotor.

Swing-Out Rotor:

In contrast, a swing-out rotor allows tubes to swing out horizontally as the centrifuge rotates. This design maintains tubes in a more horizontal position during centrifugation, leading to a different sedimentation pattern. Swing-out rotors are preferred for applications requiring gentle separation of samples, such as density gradient centrifugation and the isolation of delicate biomolecules.


Swing-out rotors are more complex than fixed-angle rotors, but they offer a number of advantages.

Swing-out rotors can be used to provide a wider range of motion than fixed-angle rotors. They can also be used to generate more torque, which can be useful in applications where high power is required.

In clinical scenarios that involve the separation of plasma and serum for clinical chemistry, swing-out rotors are typically favored. The stability of the barrier between plasma and serum components in blood makes swing-out rotors particularly suitable for such applications. However, it is noteworthy that smaller and more cost-effective fixed-angle centrifuges marketed as "clinical" centrifuges, such as the MKE Low Speed Clinical Centrifuge, are more prevalent in clinical laboratories.

Low Speed Clinical Centrifuge

Key Differences of Fixed Angle Rotor and Swing out Rotor:

The following table summarizes the differences between fixed-angle and swing-out rotors:


In terms of centrifugal material and capacity etc., fixed-angle rotors and Swing out rotors differ as follows

Sedimentation Pattern:

Fixed-Angle Rotor: Particles sediment along the tube wall.

Swing-Out Rotor: Tubes swing out horizontally, resulting in a more even sedimentation across the tube.


Fixed-Angle Rotor: Ideal for pelleting applications, such as isolating cellular components.

Swing-Out Rotor: Suitable for gentle separations, like isolating gradient layers or fragile biomolecules.

Sample Capacity:

Fixed-Angle Rotor: Typically has a lower sample capacity.

Swing-Out Rotor: Allows for a higher sample capacity due to the horizontal orientation of tubes.

Rotor Design:

Fixed-Angle Rotor: Tubes are fixed at a specific angle.

Swing-Out Rotor: Tubes can swing out horizontally during centrifugation.

Considerations for Choosing the Right Rotor:

Sample Type:

Choose a fixed-angle rotor for pelleting dense particles.

Opt for a swing-out rotor for applications requiring gentle separation.

Experimental Goals:

Consider the specific requirements of your experiment – whether pelleting or gentle separation – and select the rotor accordingly.

Sample Volume:

Evaluate the volume of your samples, as swing-out rotors often accommodate larger sample volumes.

Centrifuge Compatibility:

Ensure that the selected rotor is compatible with the centrifuge model you are using.

In conclusion, understanding the differences between fixed-angle and swing-out rotors is crucial for optimizing centrifugation protocols. The choice of whether to use a fixed-angle or swing-out rotor depends on the specific application. Fixed-angle rotors are a good choice for applications where precise control of the rotor position is not required. Swing-out rotors are a good choice for applications where a wider range of motion or more torque is required. Selecting the right rotor type can greatly enhance the efficiency and success of centrifugation processes in the laboratory.

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