A filtration cell (10) for a biological sample having an outer housing (12) defining a first chamber and an inner housing (14) defining a second chamber is disclosed. The inner housing is disposed within the first chamber and rotatable with respect to the outer housing and at least a portion of the inner housing includes a filtration membrane (52). Upon rotation of the inner housing a first portion of the biological sample passes from the first chamber into the second chamber and a second portion of the biological sample is restrained in the first chamber. Alternatively the filtration cell may also include a rotation element disposed in the inner housing. Upon rotation of the rotation element with respect to the inner housing a first portion of the biological sample to passes from the second chamber into the first chamber and a second portion of the biological sample is restrained in the second chamber.
