How Centrifugation Works


Centrifuges such as benchtop centrifuges and veterinary centrifuges are used in different laboratories to separate fluids based on density. In clinical and research laboratories, centrifuges are used for virus, protein, cell, organelle, and nucleic acid purification.

A centrifuge in a clinical setting can be used to separate whole blood components. Various assays necessitate plasma or serum which can be obtained through centrifugation. Serum is obtained by allowing a whole blood sample clot at room temperature.

From there the sample is centrifuged. The clot is also removed, which leaves a serum supernatant. Unlike serum, plasma can be obtained from whole blood treated with anticoagulants.

Principles of Centrifugation

A centrifuge works by separating particles suspended in a liquid according to rotor speed, viscosity of the medium, and particle density and size. Within a solution, gravitational force causes particles of higher density to sink. Particles that are less dense than the solvent will float to the top.

Centrifugation will take advantage of even the most minute differences in density in order to separate the particles within a solution. As the rotor spins around the central axis, it will generate a centrifugal force that moves particles away from the axis of rotation.

If the centrifugal force will exceed the buoyant forces of the liquid and the frictional force that is created by the particle, the particles can sediment.