This is very common separation method. With gradually increasing centrifugal speed or low speed and high speed separation alternately, it makes different particles have different centrifugal velocity and separate in different centrifugal time. This method is commonly used in separation of subsidence coefficient for large particles.
Differential velocity separation must select the particles sediment centrifugal force and the centrifugal time. During separation, When it keeps a certain centrifugal force during separation, it will gain the largest and heaviest particles sediments at the bottom of the centrifuge tube, separated supernatant fluid will be separated again under the increasing speed of centrifugal force, it will gain the second part bigger and heavier particles sediments with supernatant liquid which containing smaller and lighter particles, so after multiple centrifugal processing, it will separate the different particles in the liquid very well. Under this method, the gained sediment is inhomogenous, it often mixed with other ingredients, so it still need 2 ~ 3 times separation again and get a pure grain.
This method was mainly used to separate organelles and viruses in sera, the centrifuge advantage is easy to operate, it can pour out the separated supernatant and sediment after separation, it also can use a larger angle of rotor. The disadvantage is it must be separated for several times, the sediment has impurity, separation effect is poor, it cannot obtain a pure particles upon one time, the separated sediment on the bottom of the tube is easily become inactivation.
2. Density gradient zone separation (hereinafter referred to as Zone separation method) :
Zones separation method is adding inert density gradient into samples, and then separate it. The particles can be distributed to the gradient of specific position and different separation zone under a certain centrifugal force. The method advantage is: (1) the separation effect is good, can a get the pure particles; (2) the range is wide, can separate particles with differential subsidence coefficient at differential separation speed ,it also separate some different buoyancy density particles; (3) particles won't be squeezed deformation, it can keep activation and prevent mixing formed zone which caused by convection.