What is centrifugation ? Explain
briefly
Answers
Explanation:
Centrifugation is a technique used for the separation of particles from a solution according to their size, shape, density, viscosity of the medium and rotor speed. The particles are suspended in a liquid medium and placed in a centrifuge tube. The tube is then placed in a rotor and spun at a define speed.
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Explanation:
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Explanation:
Centrifugation is the technique which involves the application of centrifugal force to separate particles from a solution according to their size, shape, density, viscosity of the medium and rotor speed.[1] Not only is this process used to separate two miscible substances, but also to analyze the hydrodynamic properties of macromolecules.[2] More-dense components of the mixture migrate away from the axis of the centrifuge (move to the outside), while less-dense components of the mixture migrate towards the axis, i. e., move to the center. Chemists and biologists may increase the effective gravitational force on a test tube so as to more rapidly and completely cause the precipitate (pellet) to gather on the , allows elimination of impurities into the supernatant.
There is a correlation between the size and density of a particle and the rate that the particle separates from a heterogeneous mixture, when the only force applied is that of gravity. The larger the size and the larger the density of the particles, the faster they separate from the mixture. By applying a larger effective gravitational force to the mixture, like a centrifuge does, the separation of the particles is accelerated. This is ideal in industrial and lab settings because particles that would naturally separate over a long period of time can be separated in much less time.[3]
The rate of centrifugation is specified by the angular velocity usually expressed as revolutions per minute (RPM), or acceleration expressed as g. The conversion factor between RPM and g depends on the radius of the centrifuge rotor. The particles' settling velocity in centrifugation is a function of their size and shape, centrifugal acceleration, the volume fraction of solids present, the density difference between the particle and the liquid, and the viscosity. The most common application is the separation of solid from highly concentrated suspensions, which is used in the treatment of sewage sludges for dewatering where less consistent sediment is produced.[4]
In the chemical and food industries, special centrifuges can process a continuous stream of particle-laden liquid.
Centrifugation is the most common method used for uranium enrichment, relying on the slight mass difference between atoms of U238 and U235 in uranium hexafluoride gasMathematical formula
The general formula for calculating the revolutions per minute (RPM) of a centrifuge is
{\displaystyle RPM={\sqrt {g \over r}}}{\displaystyle RPM={\sqrt {g \over r}}},
where g represents the respective force of the centrifuge and r the radius from the center of the rotor to a point in the sample.[5] However, depending on the centrifuge model used, the respective angle of the rotor and the radius may vary, thus the formula gets modified. For example, the Sorvall #SS-34 rotor has a maximum radius of 10.8 cm, so the formula becomes {\displaystyle RPM=299{\sqrt {g \over r}}}{\displaystyle RPM=299{\sqrt {g \over r}}}, which can further simplify to {\displaystyle RPM=91{\sqrt {g}}}{\displaystyle RPM=91{\sqrt {g}}}.[6] the applied centrifugation field is square angular velocity in radians per sec, the radial distance o the particle from the axis;
The most common formula used for calculating Relative Centrifugal Force (x g) is: RCF (x g) = 1.118 x Radius (mm) x (rpm/1000)²
Many clinical separations have historically been carried out at 3000 rpm. This is a somewhat arbitrary approach as the RCF applied is dependent upon the radius in a linear fashion - so a 10% larger radius means that a 10% higher RCF is applied at the same speed. To discover the RCF that you have been applying at 3000 rpm, the above formula can be simplified to:
[Short cut for 3000 rpm, with only a 0.62% error:] RCF (x g) = 10 x Radius (mm)
Centrifugation in biological research
Microcentrifuges
Microcentrifuges are used to process small volumes of biological molecules, cells, or nuclei. Microcentrifuge tubes generally hold 0.5 - 2.0 mL of liquid, and are spun at maximum angular speeds of 12,000–13,000 rpm. Microcentrifuges are small enough to fit on a table-top and have rotors that can quickly change speeds. They may or may not have a refrigeration function.
High-speed centrifuges
High-speed or superspeed centrifuges can handle larger sample volumes, from a few tens of millilitres to several litres. Additionally, larger centrifuges can also reach higher angular velocities (around 30,000 rpm). The rotors may come with different adapters to hold various sizes of test tubes, bottles, or microtiter plates.