Sedimentation rate of a given particle is directly proportional to the size of the particle. Sedimentation rate is proportional to the difference between the density of the particle and the density of the medium in which it is suspended. Sedimentation is ZERO when the density of particle and medium are equal. If the density of the medium exceeds that of the particle, flotation of the particle will occur. Sedimentation rate is directly proportional to centrifugal force.
Sedimentation rate is inversely proportional to the viscosity of the medium.
In this method, a centrifuge tube filled with a uniform mixture of a sample is centrifuged at an appropriate speed and time. These two fractions can then be recovered simply by decanting the supernatant from the pellet. The supernatant can then be recentrifuged at a higher centrifugal force to obtain further purification, with the formation of a new pellet and supernatant. The pellet can also be recentrifuged after suspension in a small volume of a suitable solvent. Purity of fractions can be increased further by repeating the process of differential centrifugation.