Clearing factor
Encyclopedia
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
(in hours) required for sedimentation
of a fraction with a known sedimentation coefficient
(in svedberg
s):
The value of the clearing factor depends on the maximum angular velocity
of a centrifuge (in rad/s) and the minimum and maximum radius
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
factor of a centrifuge-rotor combination.
For runs with a rotational speed lower than the maximum rotor-speed, the
factor has to be adjusted:
Centrifugation
Centrifugation is a process that involves the use of the centrifugal force for the sedimentation of mixtures with a centrifuge, used in industry and in laboratory settings. More-dense components of the mixture migrate away from the axis of the centrifuge, while less-dense components of the mixture...
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
(in hours) required for sedimentationSedimentation
Sedimentation is the tendency for particles in suspension to settle out of the fluid in which they are entrained, and come to rest against a barrier. This is due to their motion through the fluid in response to the forces acting on them: these forces can be due to gravity, centrifugal acceleration...
of a fraction with a known sedimentation coefficient
Sedimentation coefficient
The sedimentation coefficient s of a particle is used to characterize its behaviour in sedimentation processes, notably centrifugation. It is defined as the ratio of a particle's sedimentation velocity to the acceleration that is applied to it .The sedimentation speed v_t is also known as the...
(in svedbergSvedberg
A svedberg is a non-SI physical unit used for sedimentation coefficients. It characterizes the behaviour of a particle type in sedimentation processes, notably centrifugation. The svedberg is technically a measure of time, and is defined as exactly 10-13 seconds A svedberg (symbol S, sometimes...
s):
The value of the clearing factor depends on the maximum angular velocity
Angular velocity
In physics, the angular velocity is a vector quantity which specifies the angular speed of an object and the axis about which the object is rotating. The SI unit of angular velocity is radians per second, although it may be measured in other units such as degrees per second, revolutions per...
of a centrifuge (in rad/s) and the minimum and maximum radiusRadius
In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...
of the rotorTurbine
A turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work.The simplest turbines have one moving part, a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they move and...
:
As the rotational speed of a centrifuge is usually specified in RPM, the following formula is often used for convenience:
Centrifuge
Centrifuge
A centrifuge is a piece of equipment, generally driven by an electric motor , that puts an object in rotation around a fixed axis, applying a force perpendicular to the axis...
manufacturers usually specify the minimum, maximum and average radius of a rotor, as well as the
factor of a centrifuge-rotor combination.For runs with a rotational speed lower than the maximum rotor-speed, the
factor has to be adjusted:-
2