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Selected Definitions Centrifugation:
It is the process in which centrifugal force is used as driving force for phase separation.
Centrifuge: The equipment used for separation is known as centrifuge. Centrifugal effect (C) or Relative Centrifugal Force: It is the ratio of the centrifugal force (F) and gravitational forces (G).
10.1 INTRODUCTION Centrifugation is the process in which centrifugal force is used as driving force for phase separation. The separation between the liquid and solid phases are on the basis of the particle size and density difference. The equipment used for separation is known as centrifuge. Centrifuges are also used for separation of macromolecules, separation of two immiscible liquids, to concentrate small molecular species, and to concentrate gases having different molecular weight. Centrifugation is widely employed when filtration process is not applicable.
10.1 APPUCATIOfIS 1. Centrifugation is widely used in bulk drug industry to separate crystalline material from suspension. 2. Centrifugation is used for isolation of bacterial cells, actinomycetes mycelium and spores from liquid growth. 3. Centrifugation is used for separation of blood cells from blood 4. Ultracentrifuge is used for separation of virus particle which are utilize in industrial applications 5. Centrifugation is used for separating drug present in blood, urine and tissue fluid. This is essential for evaluation of pharmacokinetic parameters and bioequivalence studies. 6. Centrifugation is used to obtain pure form of insulin by selective precipitating other fraction of protein and separating them by ultracentrifugation. 7. Ultracentrifugation is used to determine molecular weight of polymers, serum albumin, insulin and methyl cellulose.
10.3 PRINCIPLE OF CENTRIFUGATION The centrifuge involves the principle of sedimentation, where the acceleration at centripetal force causes denser substances to separate along the radial direction at the bottom of the tube and the lighter objects will tend move up the tube. The particle having size more than 5 urn are separated by simple filtration process while the particle having size 5 urn or less do not sediment under gravity. The centrifugal force is used to separate them.