Centrifuges are common laboratory tools used to remove particles from a solution. These particles are sorted based on the medium's size, shape, density, and viscosity. The separation process is affected by the rotor speed.
Centrifuges are one of the most common pieces of laboratory equipment nowadays. They are found in a variety of laboratories, including chemistry, biochemistry, and molecular biology labs, and are employed in both research and therapeutic contexts.
Separation, purification, and isolation of organelles, cells, and cell components, as well as more complicated mixtures of nucleic acids, proteins, and viruses for further study, are some of their most common applications.
Although centrifuges have a lengthy history—they were first used to separate cream from milk in the late 1800s—their capabilities (maximum centrifugal force) did not experience much growth until biochemistry progressed, resulting in a subsequent demand for machines with higher levels of centrifugal force.
These demands—the necessity to separate cell components, and later, an increased demand in virus research—led to various advances in centrifugation technology, eventually culminating in the commercial centrifuge.
What Is the Purpose of a Centrifuge?
Centrifuges separate heterogeneous mixtures into their many components based on their densities – liquids in liquids, solids in liquids, and liquids in gasses. The separation of red blood cells and other blood components from whole blood is one of the most popular applications.
The sedimentation principle governs how a centrifuge works. The tendency of particles in suspension to settle out of the medium where they are confined and come to rest against a barrier is referred to as sedimentation. The centrifuge separates the particles from the solution using centrifugal acceleration.
The particles will sink to the bottom of the tube if the solution has a higher density than the solvent. The particles float to the top if the solution has a lower density than the solvent.
The larger the density difference between the solution and the solvent, the faster the particles migrate. If the density between the two remains constant, the particles in the solution remain stable.
In instances when particles must be separated from a solution with little to no variation in density, the centrifuge uses centrifugal force to separate the particles rather than gravity.
What Is the Function of a Centrifuge?
A centrifuge spins liquid samples at high speeds using a motor. The rotational speed of a centrifuge's rotor is commonly written as RCF, short for relative centrifugal force, in units of gravity (x g).
Many devices, however, will indicate the speed in RPM, or revolutions per minute. The dense components are pushed to the exterior of the container by centrifugal force, allowing the solids to settle fully and quickly.
Centrifuges are classified according to their size, sample volume, and rotor type. When it comes to purchasing a centrifuge for your laboratory, the rotor type is extremely important. This is because the rotor influences the types of programs you can run.
Additionally, centrifuges use glass or plastic tubes that fit into the rotor chambers. The samples that can be utilized in the unit are influenced by the size and type of sample tubes.
Glass tubes, for example, can be used with the majority of solvents but are frequently more expensive. When used properly, plastic tubes can be just as durable; however, water is the recommended solvent. If you need to work with larger samples, you should utilize centrifuge bottles rather than tubes.
Centrifuge Types and Applications
Bench Centrifuges for Small Areas
These centrifuges, also known as tabletop centrifuges, capture small amounts of material like yeast cells and erythrocytes. Small bench centrifuges have a maximum relative centrifugal field of 3,000 to 7,000 times the gravitational force, also known as g-force (g).
These are relatively slow in comparison to other solutions. These are general-purpose centrifuges that are among the most cost-effective alternatives on the market today.
Refrigerated Centrifuges with Large Capacity
A chilled rotor chamber is standard on large capacity refrigerated centrifuges. To accommodate a different size, the rotor chambers can be changed. They capture fast sedimenting material at a maximum speed of 6,500 g, similar to tiny tabletop models.
Refrigerated High-Speed Centrifuges
High-speed centrifuges are similar to large capacity types, but they can achieve speeds of up to 60,000 g. These models may gather bigger cellular organelles, cellular detritus, bacteria, and ammonium sulfate-precipitated proteins. A refrigerated rotor chamber is also available in refrigerated variants.
Centrifuges ultrasonic
Ultra centrifuges are designed to spin at extremely high speeds, up to 1,000,000 g (9,800 kilometers per second or 6,089 miles per second). Centrifuges of this type are classified as either preparative or analytical.
Ultracentrifuges for Preparation
Preparative ultracentrifuges have a capacity of 600,000 g. They are used to determine the shape and mass of macromolecules, as well as to separate lipoprotein molecules from plasma and for a variety of other purposes. Preparative ultracentrifuges have refrigerated, sealed, and evacuated chambers.
Ultracentrifuges for Analytical Purposes
There are three optical systems available with an analytical ultracentrifuge: a light absorption system, the Schlieren system, and the Rayleigh interferometric system.
The Schlieren and Rayleigh systems are used to detect changes in the solution's refractive index, whereas a light absorption system detects changes by ultraviolet light absorption. These models weigh around 500,000 g.
