A fixed angle rotor holds tubes at a fixed angle, usually 45° during centrifugation.   The densest particles in the solution will then separate towards the angle of the centripetal force.  In many cases, dense particles will form a concentrated pellet at the bottom of the tube.  Fixed angle rotors are useful for a variety of applications from pelleting bacterial and cells to isopycnic separation of macromolecules.


In a swing out rotor, tubes are placed in buckets that are not fixed to the rotor. As spinning starts, these buckets can swing out and spin at a horizontal angle out from the axis of rotation.  This horizontal spinning allows samples to be resolved in density gradients and can promote more effective separation of individual particles.  This type of roto is not as useful in pelleting applications but it is very effective when used for the separation of solutions that contain large particles.

So, now you ask yourself, which rotor is best for me? First, consider your lab’s throughput. A Fixed Angle Rotor is capable of accommodating a great number of tubes at once so it might be better for high-volume applications.  Secondly, you should think about the spin speed that you need from your centrifuge.  Fixed angle rotors are designed to withstand much higher speeds than swing out rotors, so they are the best choice for separating biological macromolecules.

Once the rotors are in the laboratory, it is important to establish a regular rotor maintenance program. This will increase lab safety, extended rotor life span, and reduce centrifugation and contamination problems.  You should follow the manufacturer’s recommended schedule to have rotors inspected, and retire them when they show wear.  

As a leader in Scientific Equipment Repair and Medical Equipment Calibrations, Scientific Instrument Center works with many corporations, universities, and hospitals providing the highest level of laboratory services. Our team of experienced technicians are dedicated to offering reliable and accurate services. We keep your equipment performing to industry codes and regulations. 

Feel free to contact us at (614) 771-4700 to learn more about our calibration services.