Centrifugation

Centrifugation is a process which separates or concentrates materials suspended in a liquid medium. The theoretical basis of this technique is the effect of gravity on particles in suspension. 2 particles of different masses will settle in a tube at different rates in response to gravity. The centrifugal force is proportional to the rotation rate of the rotor. The centrifuge consists of a rotor and closed in a refrigerated chamber buy an electric motor.

Definition of Centrifugation

It is a unit operation working for separation separating the consequent present in a dispersion with the help of centrifugal force for example centrifugal force includes the earth revolves around the sun. It is a technique which involves the application of centrifugal force to separate particles from a solution according to their size, shape, density, the viscosity of the medium and rotor speed.

Principle of Centrifugation

1) The centrifuge involve the s principle of sedimentation.

2) The principle of the centrifugation technique is to separate the particles suspended in liquid media under the influence of a centrifugal field. These are placed either in tubes or bottles in a rotor in the centrifuge.

3) Sedimentation is a phenomenon where suspended material settles out of the fluids by gravity. The suspended material can be particles such as clay or powder. Example, tea leaves falling to the bottom in a teacup.

4) The particles having size more than 5 micrometres are separated by simple filtration process while the particles having size 5 micrometre or less do not sediment under gravity. The central force is useful to separate those particles.

Objectives of Centrifugation

1) To separate the immiscible liquids

2) To purify the component by removing impurities in the supernatant liquid.

3) To separate crystalline drugs from the mother liquor.

4) To test the emulsion and suspensions for creaming and sedimentation at an accelerated speed.

Application of Centrifugation

1) Production of bulk drugs.

2) Production of biological products.

3) Evaluation of suspensions and emulsion.

4) Determination of molecular weight of collides.

5) Separating chalk powder from water.

6) Removing fat from milk to produce skimmed milk.

7) The clarification and stabilization of the wine.

8) Biopharmaceutical analysis of drugs.

9) Use in water treatment.

10) Removing water from lettuce after washing it in a salad spinner.

11) Separating particles from an airflow using cyclonic separation.

Theory of Centrifugation

In centrifugation, centrifugal force is used as the driving force for the separation of particles. Centrifugal force is replacing a gravitational force which is responsible for the sedimentation of two particles. Thus centrifugation is useful when the ordinary filtration methods do not apply to the separation of particles. When two particles having different sizes but same densities are suspended in any liquid medium then they may not be able to separate by a simple filtration method. In such kind of cases, centrifugation method is useful.

The particle size above 5-micrometre sediment at the bottom with the help of gravity but the particles having a size less than 5 micrometres, start Brownian motion and do not sediment because of the gravity that’s why they require the centrifugal force to separate properly. The centrifugal force causes the denser dense particle direction of the radical where writer practical moves to the centre. The ratio of the force acting on radical the direction to the gravitational force is the centrifugal effect.

Process of Centrifugation

1) The centrifuge consists of a container in which a mixture of solid and liquid or two liquids is placed. Then this container is rotated at very high speed. When this container is rotated at high-speed mixture separated into its constituent parts by the action of centrifugal force on their density.

2) The solid or liquid of higher specific gravity is thrown out word with greater force.

Types of Centrifugation Techniques

1) Density gradient centrifugation

It allows separation of many or all components in a mixture and allows for measurement also. There are 2 forms of density gradient centrifugation one is rate zonal centrifugation and the second is I saw pyknic or sedimentation equilibrium centrifugation.

A)Rate zonal centrifugation – In rate zonal centrifugation the solution has a density gradient. The sample has a density therefore greater than all the layers the solution. The sample is applied in a thin zone at the top of the centrifuge tube on a density gradient. Under centrifugal force, the particles will begin segmenting through the gradient. The particles will begin segmenting in separate zones according to their size, shape and density.

B) Isopycnic or sedimentation equilibrium centrifugation – In this type of centrifugation, the solution contains a greater range of densities. The density gradient contains the whole range of densities of the particle in the sample pool stop each particle with sediment only to the position in the centrifuge tube at which the gradient density is equal to the phone density. In sedimentation centrifugation separation of particles occur into the zone based on their density difference, independent of time.

2) Differential Centrifugation

Differential centrifugation is a common procedure in microbiology and cytology useful to separate certain organelles for further analysis of specific parts of cells. In the process, a tissue temple is first homogenised generalized to break the cell membranes and mix up the cell contents. The homogenate is then subjected to repeated centrifugation, each time remove in the palate and increasing the centrifugal force.

3) Ultracentrifugation

Svedberg coined the term “ ultracentrifugation”.He was a chemist. He used the ultra fuse to determine the MW and subunit structure of emo globin. The first commercial ultra fuse was produced in 1940. An important tool in biochemical research is the centrifuge, which through rapid spinning imposes hi centrifugal forces on suspended particles, or even molecules in solution, and causes separation of such matter on the basis ultracentrifugation of differences in weight. For example, red cells may be separated from the plasma of blood, nuclei from mitochondria and cell homogenate, and one protein from another in complex mixtures.

FAQs about Centrifugation

Q.1. What is sedimentation?

Answer – Sedimentation is the tendency for particles in suspension to settle out of the fluid in which enter and come to rest against a barrier.  This is due to their motion through the fluids in response to the forces acting on them.

Q.2. How is the principle of centrifugation helpful in blood banks?

Answer- We know that blood is a colloidal solution ( neither dissolve not settle down ). In blood banks, a centrifuge machine is useful. In the centrifuge machine, a test tube with blood sample us rotated with a very high speed. Due to centripetal acceleration the heavier component settle down and the components of blood separate.

Q.3. What is a centrifugal pump?

Answer- Centrifugal pump is a hydraulic machine which converts mechanical energy to hydraulic energy by centrifugal force. It works on the principle that when pressure head increases its tangential velocity also increase.