Centrifuge is device for centrifugation to separate particles from a solution based on their size, shape, density and viscosity of the medium. It employs centrifugal force to separate phases of different densities.
It consists of rotor enclosed in refrigerated chamber which is spun by electric motor. A common feature in all centrifuges is the central motor that spins a rotor containing the samples to be separated.
Basic components of a centrifuge are:
- A metal rotor with holes in it to accommodate vessel of liquid
- A motor or alternative means of spinning the rotor a selected speed.
Types of Centrifuge
Depending on particular application, centrifuges differ in their overall design and size. The most obvious differences between centrifuges are:
- Maximum volume of samples and capacity for individual centrifugation tubes.
- Maximum speed at which biological specimens are subjected to increased sedimentation.
- Potential for refrigeration or general manipulation of the temperature during a centrifugation run.
- Presence or absence of a vacuum.
Many different types of centrifuges are commercially available including:
- Analytical ultracentrifuge.
- Large-scale clinical centrifuge.
- Refrigerated high-speed preparative centrifuge.
- Large-capacity low-speed preparative centrifuge.
- Small-scale laboratory microfuge.
- Preparative ultracentrifuge.
However, centrifuge can be broadly classified into three types:
- Low speed centrifuge
- High speed centrifuge
Low speed centrifuge
Different types of large-capacity low speed preparative centrifuges are available but they are quite demanding on space and also generate considerable amounts of heat and noise. Hence, use of small capacity desk- top centrifuges are more common in use.
Most laboratories have a standard low-speed centrifuge used for routine sedimentation of heavy particles. The low speed centrifuge has a maximum speed of 4000-5000 rpm. These centrifuges are simple, small as well as least expensive & also called as clinical centrifuge.
These instruments usually operate at room temperatures and lacks any temperature regulatory system. Two types of rotors are used in it.
- Fixed angle
- Swinging bucket.
It is used for sedimentation of red blood cells, yeast cells or bulky precipitates of chemical reactions.
High speed centrifuge
These are usually equipped with refrigeration system to remove heat generated due to friction between the air and the spinning rotor as it has higher speed of rotation. High speed centrifuge has a maximum speed of about 25,000 rpm.
The operator of this instrument can carefully control speed and temperature which is required for sensitive biological samples.
It is commonly used to collect microorganisms, cell debris, large cellular organelles, precipitates of chemical reactions, immunoprecipitates, isolating subcellular organelles such as chloroplasts, nuclei, mitochondria, lysosomes etc.
Rotors used in high speed centrifugation includes:
- Fixed angle
- Swinging bucket
- Vertical rotors
It is sophisticated, expensive and requires special rotors made up of aluminium, titanium or fiber-reinforced composites to withstand at high speeds. They have maximum speed of 75,000rpm.
As Intense heat is generated due to high speed it must be refrigerated and kept at high vacuum. Refrigeration system can maintain temperature between (0-4)0C. 2 pumps work in tandem making it possible to attain and hold vacuums of 1-2 µ.
It is an important tool in biochemical research & through rapid spinning imposes high centrifugal forces on suspended particles, or even molecules in solution and causes separations of such matter on the basis of differences in weight.
It can be used for both preparative as well as analytical studies for decisively advanced detailed biochemical analysis of subcellular structures and isolated biomolecules.
Besides, these centrifuge, microfuge is a type of centrifuge which is mainly used to collect small volume of samples in biochemistry/biology/molecular biology lab. E.g. To concentrate protein samples.
Refrigerated and non-refrigerated microfuges are available. To prevent denaturation of protein samples, non-refrigerated microfuges are often used in old rooms. It have centrifugal fields of approx. 10,000g and sediments biological samples in a minute.
Download link: Centrifuge and its types.pdf