Search
Generic filters

Fixed Angle vs. Swing Out Rotors: What’s the difference?

Swing out centrifuge rotor with four blue sample buckets

What is the difference between fixed-angle and swing-out centrifuge rotors?

The names are something of a giveaway in this comparison: Fixed angle centrifuge rotors are designed to hold samples at a fixed angle while the rotor spins. This is typically around 30-45°, but depends on the individual rotor. Swing out rotors on the other hand hold sample buckets on an axle allowing the sample to swing outwards at a varying angle, depending on the RPM (revolutions per minute, or ‘speed’) and RCF (relative centrifugal force, g).

Centrifuges are used to separate materials by density. As the rotor spins, the denser part of the sample is pulled toward the bottom of the tube, at an angle defined by the centrifugal force. This means that solids, or denser materials, will be pulled directly to the bottom of the tube in a swing-out rotor, but usually collects at an angle at the bottom of the tube in a fixed angle rotor.

Diagram showing pellet differences when using swing out or fixed angle centrifuge rotors.
Pellet difference for swing out or fixed angle centrifuge rotor. The pellet forms perpendicular to the direction of the centrifugal force.

Comparison of fixed angle vs. swing out rotors

Fixed angleSwing out
Holds samples at ‘fixed angle’ – typically around 45 degrees to the groundSamples are free to swing out at various angles depending on the centrifugal force
Sediment forms at an angle on the tubeSediment forms at the bottom of the tube
Can usually withstand higher centrifugal force than swing out rotorsTypically withstands a lower centrifugal force than fixed angle
Tends to hold more samples due to more efficient sample spacingTends to hold fewer samples to accommodate ‘swing out’ space
Example of fixed angle rotor:
Frontier Rotors 1 600x600
Example of swing out rotor:
Swing out Rotor 4x100ml Auto ID 30314822 DMX ID 4294984179 WebShop

Which type of centrifuge rotor do I need?

There’s an argument that swing out rotors offer the best separation location within the container: By ensuring the sediment settles at the bottom of the tube it reduces the risk of sediment getting swept back up into the supernatant. This is ideal for separations prior to sensitive analysis such as LCMS, where solid residue may cause errors; or other applications requiring extremely precise separation. Swing out rotors are also used for gradient centrifugation, as the gradient layers are able to stay in position as the centrifuge stops spinning. Swing out rotors are also needed for centrifugation of plates.

Fixed angle, on the other hand, are often the rotor of choice for separating biological material such as DNA, as this requires a greater centrifugal force, which fixed angle rotors can accommodate. Higher RCF is also desirable when very compact pellets are required, since the sediment is formed at greater pressure. Additionally, if the centrifugal force is higher, there is generally less time required for centrifugation. This can be important for processing large sample numbers.

If you would like help choosing the which centrifuge rotor is best for your application, give our team a call on 01257 270 433

Stock image of swing out centrifuge rotor holding samples