Comparison of different types of rotor for density-gradient techniques.

Centrifugal separations can be classified into three categories, namely differential pelleting, rate-zonal centrifugation and isopycnic centrifugation. Although differential pelleting is the most widely used technique, it has only a limited potential for providing the investigator with purified material. Thus only the last two techniques, both of which involve separations on density gradients, can be used to obtain homogeneous populations of particles.