What is a centrifuge?

Centrifuge is a device that separates the components of liquids, gases and solids based on their density difference by centrifugal force. thisSeparation is achieved by rapid rotation of a rotor (moving parts of an electromagnetic system that is placed in an electric motor, alternator, and electric generator) containing the sample tubes. Centrifugal force drives heavier materials outward from the center of the rotor.

This rotation causes materials and particles that have a higher density to move outward in the radial direction, and at the same time, materials that have a lower density are displaced and move towards the center, but in a laboratory centrifuge, radial acceleration causes dense particles go down the pipe . Sometimes a centrifuge can be a suitable filter to remove contamination from the main body of liquids.

Centrifuge components

Its most important components are the electric motor, rotor, timer, device shaft, speed controller, key and tachometer, which determines the number and amount of revolutions.

The basis of the work of the centrifuge

Samples rotate around a center at a certain speed. A force enters the samples in the direction perpendicular to the direction of rotation and toward the outside of the center, which is known as centrifugal force.

Centrifuges exist in most laboratories, including academic, research, and clinical laboratories, which are used to purify and separate cells, intracellular organelles, proteins, nucleic acids, and viruses.

Of course, there are other centrifuges that are designed purely for industrial applications, but in the end, the use of all of them is the same and for separating different components of materials.

The main part of the centrifuge is the rotor, whose structure and rotation speed are a suitable criterion for classifying centrifuges.

Types of centrifuges and applications

Laboratory centrifuge: This model with a smaller size is often used to separate different components of biological or chemical materials, which consists of a rotor with angled holes for storing samples, and its types are mentioned below.

Since the most important factors affecting the efficiency of the rotor are the maximum rotation speed  (rpm), the maximum radius (r _max ) and the minimum radius (r _min ), all of which affect the amount of centrifugal force and centrifugation time.

k is a factor or coefficient that relates these factors together and with its help, the time required for the samples to settle in the test tube can be obtained.

Centrifuge with constant rotation angle : this model has no moving parts, so it is exposed to less tension, which causes more centrifugal forces and less time, although the variety of sample tubes and containers in this model is limited and relative to the axis The rotation has a constant angle that the placement of the sediment is completely dependent on the same angle and this angle varies between 25 and 45 degrees, and naturally, as this angle increases, the sediments are denser and less scattered.

Centrifuge with variable rotation angle: unlike the above model, this centrifuge brings a variety of containers with different volumes from 1 to 100 liters due to the presence of more diverse adapters.

In this model, due to the variable angle, the rotor tension increases and its weight exerts pressure on the rods and grooves, as a result, the centrifugal force will be less and the centrifugation time will be longer.

During the rotation of these rotors, when the pipes are horizontal, the suspended particles are directed to the end of the pipe and the sediment is deposited in the form of single layers and uniformly. At the end of the process, the pipes return to the vertical position and the sediments at the end of the pipe and the clear solution are placed on them, as a result, it will be easier to collect and separate these sediments from the sediments formed on the wall.

Microcentrifuge:  This model is used to study biological materials and cells in small volumes between 0.5 and 2 mm. Microcentrifuges for routine laboratory applications typically spin at speeds around 16,000xg, while for more specialized applications they can reach speeds as high as 30,000xg.

High-speed centrifuge:  This centrifuge is the opposite of the microset model and is used for volumes of 10 mm and above. One of the features of this device is the simultaneous accompanying of the rotor with the converter, which increases the access to the laboratory tubes.

Industrial Centrifuge: This type is mostly used for water purification, drying of material moisture and separation of colloidal components, which is based on sedimentation and sedimentation of materials.

Ultra Centrifuge: This device is used to analyze and examine biological particles using the same centrifugal force. This centrifuge has a very high speed and is able to separate the smallest components such as ribozymes, viruses and proteins. As one of the applications of ultracentrifuge, it can be mentioned to separate the internal components of blood serums to reduce their turbidity.

Unlike microcentrifuges, which separate particles in batches, ultracentrifuges can separate particles both continuously and discontinuously. In addition to the possibility of purification, AUC ultracentrifuge can be used to determine the properties of macromolecules such as mass, shape, composition and conformation.

A type of this model for uranium enrichment is also a suitable choice, which is used for the extraction and purification of uranium from ore and is known as a gas centrifuge or cores.

Differential centrifugation: In this model, the centrifugal force increases continuously and gradually in a certain period of time, and its job is to separate organelles, cell membranes, and mitochondria (in general, cell extracts).

Density gradient centrifuge: This centrifuge is one of the best models for separating particles, which, according to the explanations we had in the first part of the article, is also a suitable measure for measuring the density of molecules in the mixture, and finally, the existing particles, according to their density along Tubes are placed.

Contrary to the mentioned conditions, sometimes, unwanted sediments are created, the reason for this problem is the unwanted accumulation of particles. Another problem is the sedimentation of solution droplets containing particles, which is due to the time when the solution layer is a suspension and this solution moves on layers that have a higher density, in which case the solution either has a low density gradient or no gradient at all. is

Refrigerated centrifuges: This model is an ideal device for temperature-sensitive samples. For example, these centrifuges are used in examining living cells of animals or proteins. Most of them have variable rotors and adapters to accommodate a wider range of samples from 1 to several liters. The speed in this example is very different and may reach xg60000 in some models.

Vacuum centrifuges: This device is a more advanced type and can use both vacuum and centrifugal force, temperature and gas to remove liquid solvents for the purity of samples. (Vacuum mechanism with heating system is used to evaporate and remove solvents) This sample is used to purify or prepare micromolecules, proteins, peptides, nucleic acids and other compounds.

Cell washing centrifuges: This model is used to wash blood cells in the commiss test or antiglobulin test, which is taken to identify antibodies attached to the surface of red blood cells. In addition, this device is used for tests such as blood group determination, body compatibility before injection, and Rh factor identification.

Clinical centrifuge: This device is used to separate different biological compounds and in medical science, such as examining blood cells, which has different types such as cytology or cytology and hematocrit.

Cytology: It is used to break cells and study cellular components, such as uterine mucosa cells.

Hematocrit: used to measure blood hematocrit (the ratio of the volume of red blood cells to the total volume of blood).

From the series of other applications of centrifuge, the following can be mentioned:

• Separation of fat from milk
• Separation of gypsum powder from water
• Separation of particles from air flow
• Separation of urea and blood components in laboratories

Centrifuge maintenance conditions

Centrifuges are expensive laboratory equipment, so to keep them healthy, we must follow some points:

The first point is how to clean and disinfect them, which if not done correctly can lead to wear or corrosion.

The next point is the method of decontamination, which means removing blood, environmental pollution or various solutions that remain in the seams and layers of the centrifuge; If they are not cleaned properly, in addition to wear, they bring diseases and risks to employees.

In the following, due to the vastness of the content, we point out some important points in a list-like manner:

• to sterilize
• Lubrication
• Considering the resistance of the rotor against the chemical substance
• Attention to aerosols

Finally, we realized that the centrifuge is one of the most important devices for separating particles and molecules with a very high variety and wide efficiency, and knowing how each of its types works and works will lead to an increase in lifespan and productivity.

Even though the centrifuge is considered one of the best methods for separating material components, there are alternative methods in the industry such as filtration, screening, distillation, decanting, and chromatography, and this choice depends on the properties and volume of the sample.