centrifugation Centrifugation is a mechanical process which involves the use of the centrifugal force to separate particles from a solution according to their size, shape, density, medium viscosity and rotor speed. The denser components of the mixture migrate ...

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 Sedimentation is the deposition of sediments. It takes place when particles in suspension 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 t ...

of a fraction with a known

sedimentation coefficient The sedimentation coefficient () of a particle characterizes its sedimentation during centrifugation. It is defined as the ratio of a particle's sedimentation velocity to the applied acceleration causing the sedimentation. : s = \frac The sedi ...

s

(in

svedberg A Svedberg unit or svedberg (symbol S, sometimes Sv) is a non- SI metric unit for sedimentation coefficients. The Svedberg unit offers a measure of a particle's size indirectly based on its sedimentation rate under acceleration (i.e. how fast a ...

s): :

t = \frac

The value of the clearing factor depends on the maximum

angular velocity In physics, angular velocity or rotational velocity ( or ), also known as angular frequency vector,(UP1) is a pseudovector representation of how fast the angular position or orientation of an object changes with time (i.e. how quickly an objec ...

\omega

of a centrifuge (in rad/s) and the minimum and maximum

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

r

of the

rotor Rotor may refer to: Science and technology Engineering *Rotor (electric), the non-stationary part of an alternator or electric motor, operating with a stationary element so called the stator *Helicopter rotor, the rotary wing(s) of a rotorcraft ...

: :

k = \frac \times \frac

As the rotational speed of a centrifuge is usually specified in

RPM Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is a unit of rotational speed or rotational frequency for rotating machines. Standards ISO 80000-3:2019 defines a unit of rotation as the dimension ...

, the following formula is often used for convenience:"Basics of Centrifugation"
/ref> :

k = \frac

Centrifuge A centrifuge is a device that uses centrifugal force to separate various components of a fluid. This is achieved by spinning the fluid at high speed within a container, thereby separating fluids of different densities (e.g. cream from milk) or ...

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: :

k_ = k \left( \frac \right)

² The K-factor is related to the sedimentation coefficient

S

by the formula:

T = \frac

Where

T

is the time to pellet a certain particle in hours. Since

S

is a constant for a certain particle, this relationship can be used to interconvert between different rotors.

\frac = \frac

Where

T_1

is the time to pellet in one rotor, and

K_1

is the K-factor of that rotor.

K_2

is the K-factor of the other rotor, and

T_2

, the time to pellet in the other rotor, can be calculated. In this manner, one does not need access to the exact rotor cited in a protocol, as long as the K-factor can be calculated
Many online calculators
are available to perform the calculations for common rotors.

References

External links

Beckman Coulter lab resources
and manuals

of th

Laboratory techniques Unit operations {{fluiddynamics-stub