- Clearing factor
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In centrifugation the clearing factor or k factor represents the relative pelleting efficiency of a given centrifuge rotor at maximum rotation speed. It can be used to estimate the time t (in hours) required for sedimentation of a fraction with a known sedimentation coefficient s (in svedbergs):
The value of the clearing factor depends on the maximum angular velocity ω of a centrifuge (in rad/s) and the minimum and maximum radius r of the rotor:
As the rotational speed of a centrifuge is usually specified in RPM, the following formula is often used for convenience:
Centrifuge manufacturers usually specify the minimum, maximum and average radius of a rotor, as well as the k factor of a centrifuge-rotor combination.
For runs with a rotational speed lower than the maximum rotor-speed, the k factor has to be adjusted:
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References
- Beckman Coulter lab resources and manuals
- Appendix F of the Cell Biology Laboratory Manual
Categories:- Laboratory techniques
- Unit operations
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