Centrifugation Definition, Principle, Types & Applications

Centrifugation is a common process used in science labs to separate mixtures. You may have seen a washing machine spinning clothes. Centrifugation works in a similar way by using fast spinning to separate heavier and lighter parts of a mixture. It is especially useful in biology and chemistry to separate things like cells, blood, or proteins. In this article, you’ll learn what centrifugation is, how it works, the different types, and where it’s used in real life and lab work.

What is Centrifugation?

A technique for separating mixtures that makes use of spinning and centrifugal force is called centrifugation. The force that is generated when anything rotates or spins is known as centrifugal force. Particles can be divided by several characteristics during centrifugation, including size, shape, density, and viscosity.

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Materials suspended in a liquid media can be separated or concentrated using the centrifugation process. The impact of gravity on suspended particles serves as the conceptual framework for this method. In response to gravity, particles with different masses settle in a tube at various rates based on their densities. The centrifuge is a device used for the process of centrifugation to separate different materials. The most common example of centrifugation is a washing machine that separates water from clothes based on their densities as water has lower density than clothes . Other examples are the application of a centrifuge in the production of cream from milk, the separation of blood particles into RBCs, WBCs, Platelets and Plasma is also done by using centrifuge in which the red blood cells (RBCs) being the heavier precipitate first followed by WBCs, Platelets and Plasma. Centrifugation is also used in urine materials testings, and the purification of beverages.

The process of centrifugation is based on the following principle:

• The idea behind the centrifugation process is to use a centrifugal force to separate particles suspended in liquid media. These are put in a rotor of the centrifuge either in tubes or containers.
• The centrifuge operates according to the sedimentation principle, which states that the less dense materials and particles flow outward in the radial direction as a result of centripetal acceleration. The influence of centrifugal force and gravity causes suspended material to separate from fluids in this process.
• Particles in a solution having a greater density than the solvent sink to the bottom as sediment, while those that have a density lower than the solvent float to the top. The larger the density difference, the more quickly they move.

Types of Centrifugation

There are several techniques of centrifugation available for the separation of materials but the most common types are as follows:

1. Differential Centrifugation

In the domains of biochemistry and cell biology, differential centrifugation is frequently used to separate organelles and other subcellular particles according to their rates of sedimentation.

In differential centrifugation, a tissue sample must be churned out or lysed first to break open the cell membranes, release organelles, and release cytosol. The lysate is then centrifuged many times.

Particles that can dissolve under specific centrifugal conditions for a fixed period create an elongated “pellet” at the base of the centrifuge tube. After each centrifugation, the supernatant (non-pelleted solution) is taken out of the tube and centrifuged once more, but with a stronger centrifugal force and/or longer separation time.

2. Density Gradient Centrifugation

A procedure in which the components of a sample are separated based on their densities by employing the centrifugal force in a dense medium or density gradient created inside a centrifuge is known as the density gradient centrifugation.

The principle of density gradient centrifugation is the idea that molecules will settle down through centrifugal force until they encounter a medium with a density with the same density as their own.

The density gradient centrifuge is further divided into two types:

• Isopycnic Centrifugation
• Rate Zonal Centrifugation

3.Isopycnic Centrifugation

In isopycnic centrifugation, the only factor used to separate particles is their density. Depending on the size of the particles, the particles migrate in a downward direction. Once the particle’s density reaches parity with that of the medium it stops flowing. While descending through the tube toward the bottom, the density of the gradient rises. As a result, the less dense particles form bands above the denser particles, which are followed by the denser particles that fall to the bottom.

Since this is directly dependent on the buoyant densities and not the particle sizes, it is regarded as a true equilibrium. Therefore, it is also known as buoyant or sedimentation equilibrium centrifugation.

4. Rate Zonal Centrifugation

Particles are separated by size and shape using rate zonal centrifugation. By stacking the sample as a small zone on top of a density gradient, the problem of cross-contamination of particles with differing sedimentation rates can be avoided in rate-zonal centrifugation. In this method, unlike in differential centrifugation, the faster sedimenting particles are not contaminated by the slower ones. Size and shape are the main factors used to divide the particles. The rate of sedimentation of a particle increases with its size. Particle deposits more quickly the more spherically symmetrical it is. The rate at which the particles settle through the gradient depends on the sedimentation coefficient of the particle or material.

Types of Centrifuges and Their Uses

Centrifuges come in different types, each designed for specific tasks in labs. It’s

• • Microcentrifuge- Used to spin liquids samples(like in tiny test tubes). It is commonly DNA or protein labs.

• High Speed Centrifugate- Spins faster than a microcentrifugate and can handle bigger tubes. It’s useful for separating cell parts, proteins, and other medium sized particles.

• Ultra centrifugate- This is the fastest type of centrifuge. It’s used for very tiny particles like viruses or molecules. Often used in advanced research.

• Refrigerated Centrifugate- Keeps samples cool while spinning. This is important for temperature-sensitive materials like enzymes or blood.

Difference Between Filtration & Centrifugation

Filtration and centrifugation have quite similar applications but both the processes differ from each other in several ways:

Filtration	Centrifugation
The process of eliminating undesirable elements from a liquid based on their size is called filtration.	The process of removing lighter components from a mixture or solution based on their densities is known as centrifugation.
It works under the effect of gravitational force.	The centrifugal force is responsible for the separation of particles.
In this process, sieves, perforated layers, strangers, filter funnel, or membranes are used for filtration.	A centrifuge machine and centrifuge tubes are the important components required for the conduction of this process.
The main goal of filtration is to get the desired result by eliminating contaminants from a mixture or separating larger insoluble solids from a mixture.	The separation of solids or denser particles from a solution is the main objective of centrifugation.
It is less efficient and takes more time to separate the material.	It is more efficient than filtration as separation occurs more quickly.

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