2. Introduction
• There are different types of centrifuge in
which there are two main categories that are:
1. Based on speed
a. Low speed
b. High speed
c. Ultra speed
2. Based on angle
a. Fixed angle
b. Vertical
c. Swing bucket
3. Based on rotors' speed
1. Low speed
centrifuge
Its speed is about
6000 rpm.
It can be operated at
room temperature.
4. 2. High speed centrifuge
It has speed up to 20k
to 30k
While operating the
centrifuge we can
control the temperature
as per our need.
6. Based on Rotors' angle
1. Fixed angle rotors
In fixed-angle rotor, the sample tubes are held fixed at the angle of the rotor cavity.
When the rotor begins to rotate, the solution in the tubes reorients to affect the separation.
This rotor is most used for pelleting by differential separation of biological particles.
It is also useful for isopycnic separations of macromolecules such as nucleic acids.
7. 2. Vertical rotors
In vertical rotor, sealed tubes are held parallel to the axis of rotation.
Samples are not separated down the length of the centrifuge tube, but across the diameter
of the tube.
The isopycnic separation time is shorter in this rotor as compared to swinging bucket
rotor.
This rotor is not suitable for pelleting applications but is most efficient for isopycnic
separations due to the short pathlength.
Most common applications are isolation of plasmid DNA, RNA, and lipoproteins.
8. 3. Swing bucket rotors
In swinging bucket rotor, the sample tubes are loaded into individual buckets that hang
vertically while the rotor is at rest.
When the rotor begins to rotate, the buckets swing out to a horizontal position. This rotor is
useful when samples are to be separated based on density gradients.
This rotor is inefficient for pelleting.
10. The different types of centrifuges are as follows:
1. Small benchtop centrifuges have a maximum rate of 3000 g–7000 g. They are used to precipitate
coarse granules, yeast cells, and so on.
2. Large-capacity refrigerated centrifuges have a maximum rate of 6500 g with a capacity of 100 cc. They
are refrigerated to control the temperature.
3. High-speed refrigerated centrifuges have a maximum rate of 60,000 g; are refrigerated; and are used to
sediment small microorganisms, cellular debris, and large cellular organelles.
4. Continuous-flow centrifuges are unlike other centrifuges where tubes are attached to the rotor; in
continuous-flow centrifuges, the rotor itself is tubular. Particles are sedimented against the wall of the
centrifuge and supernatant continuously flows out; they are used in the large-scale harvesting of bacteria.
5. A preparative ultracentrifuge has a maximum rate of 600,000 g. The rotor chamber is refrigerated,
sealed, and evacuated to minimize heat production due to friction between air and the spinning rotor.
11. 6. In an analytical ultracentrifuge, a sample being spun can be monitored in real time
through an optical detection system, using ultraviolet light absorption and/or interference
optical refractive index sensitive system known as the Schlieren optical system or the
Rayleigh interferometric system. This allows the operator to observe the evolution of the
sample concentration versus the axis of rotation profile as a result of the applied
centrifugal field. With modern instrumentation, these observations are electronically
digitized and stored for further mathematical analysis. Two kinds of experiments are
commonly performed on these instruments: (1) sedimentation velocity experiments and
(2) sedimentation equilibrium experiments. An analytical ultracentrifuge has a maximum
rate of 500,000 g.
