Centrifugation is a method for separating solids from liquids of different densities in a mixture , provided the former are insoluble, using rotational or centrifugal force. For example :the washing machine, DNA separation, drying of solids.
For this purpose, an instrument called a centrifuge is often used , which rotates the mixture on a fixed and determined axis.
As its name suggests ( centrifugal : away from the center), this force tends to draw the denser components away from the axis of rotation , leaving the less dense components at the very center. It is the opposite of the centripetal force.
See also: Chromatography
Types of centrifugation
- Differential. Based on the difference in density of substances , this is a basic but inexact technique .
- Isopycnic. This technique is used, for example, to separate particles of similar size but with different densities.
- Zonal . The difference in the sedimentationspeed of substances (due to their different masses) is used to separate them within a given centrifugation time.
- Ultracentrifugation. Its power allows the separation of molecules and subcellular substances.
Examples of centrifugation
- The washing machine. This appliance uses centrifugal force to separate clothes (solid) from water (liquid) based on their densities. Therefore, clothes are usually almost dry when removed from the machine.
- Dairy industry. Milk is centrifuged to separate its water and lipid content , the latter of which is used to make butter, or from the remainder, skimmed milk.
- Cars on a curve. When we drive fast through a curve in the road, we often feel a force pulling us outward, away from the axis of the curve. This is centrifugal force.
- Obtaining enzymes. In the medical and pharmaceutical industries , centrifugation is often used to obtain certain enzymes from the specialized cells that produce them.
- DNA separation. Isopycnic centrifugation is often used in genetic laboratories to separate cellular DNA and allow for further study and manipulation.
- Foods for celiacs. When it comes to separating gluten protein from foods that contain it, centrifugation is essential. It is performed on starch paste, whose gluten content reaches 8%, and is reduced to below 2% through successive selective centrifugations.
- Blood tests. A centrifuge is used to separate the elements in the blood, such as plasma and other elements commonly found in it.
- Sedimentation acceleration. In various food industries, such as brewing and grain processing , centrifugation speeds up the sedimentation processes that gravity spontaneously generates, reducing the waiting time for raw materials .
- Latex cleaning. In the latex industry, cleaning the substance, whose surface is particularly prone to the adhesion of other particles, is necessary. This is accomplished through centrifugation, given the substance’s low density.
- Drying of solids. Another industrial application of the centrifuge is the drying of crystals or other materials obtained with water. As the centrifuge spins, the water separates from the solids and is discarded, leaving the desired solids without the liquid.
- Wastewater treatment. Centrifuging contaminated water extracts dense substances, not only solids but also oils, grease , and other unwanted components, which, once centrifuged, could be discarded.
- Amusement parks. Many amusement park rides employ centrifugal force to create a vacuum effect on their riders, who are rapidly spun around a fixed axis, tightly secured in a seat that prevents them from being thrown off the axis of rotation.
- Stunt riders. A classic circus stunt, the rider in a sphere is able to ride across the roof of the sphere, defying gravity. This is achieved after spinning many times on a horizontal axis, building up speed and subjecting himself to the centrifugal force that holds him to the inside of the sphere. Eventually, this force will be so strong that he will be able to verticalize his movement and defy gravity.
- Incline of railroad tracks. To counteract centrifugal force, railroad tracks are often inclines inward on curves, providing resistance so that the railroad does not succumb to the outward force and derail.
- The Earth’s rotation. The reason the Sun’s gravitational pull doesn’t push us headfirst into its interior is also due to the centrifugal force, which, as it rotates on the Sun’s axis, pushes it outward, counteracting and balancing the gravitational pull.
