A centrifuge is a piece of laboratory equipment that separates gas or liquid of minute density difference or same density through spinning the sample around a specific axis. It is a motor-driven device that provides a high spinning speed to the samples.
Uses of centrifuge
It is widely used in hospitals, nursing homes, and laboratories to separate liquid and gas samples. The basic use of centrifuge is seen in the case of the cell, organelle, virus protein, and nucleic acid purification. For separating whole-blood components, a centrifuge is a very widely used device.
Principle of Laboratory centrifuge
It works on the sedimentation principle. A centrifuge separates the sample by use of centripetal force. The rotor exhibits this force when it spins around a central axis. This force leads the particles to move away from the central axis. Apart from this force, there are also two types of force-
1. Buoyant force exhibited by liquid media
2. Frictional force exhibited by the sample particles
When centrifugal force is greater than these two forces, the particle will sediment. This force leads the heavier or denser substance to move away from the central axis, i.e., outward in a circular motion, whereas lighter substances move to the central axis.
Centrifuges used in laboratories:
There are various types of Laboratory centrifuges available for separating samples, but all of them work on the same sedimentation principle. Some of them are described below
1. Microcentrifuge: Microcentrifuge has a smaller footprint than others. It requires very little installation. The design of this centrifuge is very compact. It efficiently works with smaller tubes (up to 2 ml) and is used in biological fields. It is mainly used for separating pelleting protein and microfiltration of the same minor aqueous samples. The rotor also varies in size in this type of centrifuge.
2. Refrigerated centrifuge: Some samples need to be kept at a constant temperature or between temperature ranges. For handling this type of centrifuge, it is necessary to keep it at its maximum high speed without changing the temperature range. The temperature range fluctuates between -20 to 40 C. Maximum speed that the centrifuge can achieve is 30000 rounds/ min, producing 65000g centrifugal force. The centrifuge configuration may vary, such as swing bucket, fixed angle, or both.
3.Ultracentrifuge: This can accelerate speed greater than high speed refrigerated centrifuge i.e. - up to 1000000g (9800km/s2). As it runs at extremely high speed, it is capable of separating a sample of very minute differences such as protein and nucleic acid. Ultracentrifuge are of two types-
● Preparative ultracentrifuge: This type of ultracentrifuge produces relative centrifugal force up to 60 000g. It is widely used for separating particles on a density basis. Example - macromolecules and lipoprotein fraction from plasma. Preparative ultracentrifuge is equipped with various types of rotors that have the capacity of varying degrees.
● Analytical ultracentrifuge: This special centrifuge is where an optical detection system is installed. This system is made up of scanning visible light that helps to see the sample. This system allows real-time monitoring of the sample, thus watching the sedimentation process. It can produce 500000g of maximum centrifugal force.
Various types of optical systems are used here. Some of them are-
● The light absorption system
● The alternative Schlieren system
● Rayleigh interferometric system
4.PRP/PRF Centrifuge-A centrifuge that is common in dentists, aesthetics institutes and hair transplant institutes, allows the plasma to be separated from the patient's blood.
5.Blood Centrifuges-Suitable for removing plasma that is used for healing and reducing pain in various medical fields
Rotors For a Centrifuge
Rotors are the equipment within a centrifuge that rotates and generates centrifugal force. There are various types of rotors used in different kinds of centrifuges to meet the requirements of the sedimentation process. Some of them are described below-
1. Elutriator rotor: This rotor is highly modified and incorporates two technologies. It is used to separate multi particles from a single cell using two opposite forces- centrifugal l force and weight velocity.
2. Corrosion-free rotors: The most commonly used rotor in maximum centrifuges for biology purposes. It is durable and long-lasting. Also, it doesn't contaminate the material.
3. Fixed angle rotors: The rotors body in this type of rotor are placed vertically between 14 to a 40-degree angle
4. Swinging bucket rotor: The buckets (that hold the sample) are in a vertical position in the resting phase and a horizontal position with the starting of acceleration
5. Vertical tube rotors: The rotor tubes remain vertical in the aspect of the rotor body all the time regardless of rotation.