CENTRIFUGE

By

Smt Shilpa Bandrad

Dept of Microbiology

Smt. V. G. Degree College for Women

​

INTRODUCTION

• A centrifuge is an instrument which can produce centrifugal force because of the accelerated rotation around an axis.
• Centrifuge makes use of centrifugal force & brings about sedimentation (separation) of particles based on their density.
• A centrifuge is a device for separating particles from a solution according to their size, shape, density, viscosity of the medium & rotor speed.
• In a solution, particles whose density is higher than that of the solvent sink (sediment), and particles that are lighter than it float to the top.

CENTRIFUGE ROTOR

• A centrifuge rotor is the rotating unit of the centrifuge, which has fixed holes drilled at an angle.
• Test tubes are placed inside these holes and the rotor spins to aid in the separation of the materials.

​

​

TYPES OF ROTORS

1. Analytical rotor-
1. Rotors used for analytical purposes are constructed in such a way so that light which is used for determining the position of the solute boundary can pass through the sample and the container when the rotor is spinning.

2. Preparative rotor-

• Preparative rotors are of three types

1. Angle rotor-
1. Here sample tubes are inserted into cavities in the rotor, that are constructed at an angle to the axis of rotation.

​

2. Swinging bucket-
1. Tubes are located in bucket.
2. They will be not rigidly attached to the rotor.
3. The sample tubes are placed in holders which is attached to the rotor body by a pair of yokes.
4. The metal holder are allowed to swing.

​

c. Zonal rotor-

• The container tubes are parallel to the rotor axis but at operational period.

​

​

TYPES OF CENTRIFUGE

1. Bench top centrifuge-
1. These are frequently used

in microbiological lab.

• These are simple, small

and least expensive.

• Max. speed – 3000 rpm.
• Used to collect rapidly

sedimenting substances such as RBC, yeast cells or bulky ppt of chemical reactions.

2. High speed centrifuge-

• Max speed – 25,000 rpm.
• Equipped with

refrigeration to remove

heat generated due to

friction between the air

& the spinning rotor.

• Used to collect micro organisms cell debris, cells, large cellular organelles.

​

3. Ultra centrifuge-

• Max speed – 75,000 rpm.
• Has refrigeration system

to maintain the

temperature.

• Used for sedimentation of

cell fraction like ribosomes, ER.

• Viruses can also be isolated in pure form.
• DNA, RNA & proteins can be analysed completely.

​

​

​

​

THANK YOU