The Principle Of Centrifugation

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Centrifugation is a process used to separate or concentrate materials suspended in a liquid medium. It is a method used to separate molecules under the centrifugation field based on their sedimentation rate with the help of centrifugal force. It is also used to measure the physical properties of a molecule like molecular weight, density, shape, etc. If it is used for the separation of one type of materials from others is termed as preparative centrifugation and when used for measurement of physical properties of macromolecules, then it is known as analytical centrifugation.

Principle of centrifugation:
Particles suspended in a solution are pulled downwards by Earth’s gravitational force. In a solution, particles with higher mass
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It has units of seconds. A sedimentation coefficient of 1x10-13 seconds is defined as one Svedberg, S.

• The sedimentation velocity of a particle is directly proportional to its phase.
• A dense particle moves more rapidly than a less dense one because the opposing buoyant force is smaller for a dense particle.
• The sedimentation velocity depends also on the density of the solution (ρ). Particle sinks when vρ1. Relative Centrifugation Field: Particles suspended in a fluid move under the influence of gravity, towards the bottom of the vessel at a rate that depends on their size and density. Centrifugation utilizes centrifugal forces which are greater than the Earth’s gravitational force and is achieved by spinning the vessel containing the fluid and particles about an axis of rotation so that the particle experiences a centrifugal force acting away from the axis. This force is measured in terms of Earth’s gravitational force and is known as relative centrifugation
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This process is mainly used for separation of sub-components.

fig: differential centrifugation of various particles based on sedimentation rate.

In this process, the broken cells is poured into a centrifuge tube and is initially centrifuged at low centrifugal force long enough to completely sediment the largest and heaviest sub-cellular component. The supernatant obtained is carefully decanted and the above step is repeated and centrifugal force and time is increased successively at each ensuring step to sediment the lighter components and

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