(i) Chromatography is a technique of separation of biomolecules involves a sampling mixture containing biomolecules being dissolved in a mobile phase (which may be a gas, a liquid or a supercritical fluid) due to their differential adsorption over an adsorbent medium. The mobile phase is then forced through an immobile, immiscible stationary phase. The phases are chosen such that components of the sample mixture have differing solubilities in each phase.
A component which is quite soluble in the stationary phase will take longer to travel through it than a component which is not very’ soluble in the stationary phase but very soluble in the mobile phase. As a result of these differences in mobilities, sample mixture components will become separated from each other as they travel through the stationary’ phase.
Techniques such as H.P.L.C (High Performance Liquid Chromatography) and GC. (Gas Chromatography) use columns—narrow tubes packed with stationary phase, through which the mobile phase is forced. The sample is transported through the column by continuous addition of mobile phase. This process is called elution. The average rate at which an analyte moves through the column is determined by the time it spends in the mobile phase.
(ii) Centrifugation is a process that involves the use of the centrifugal force for the sedimentation of the components of a mixture with a centrifuge. More-dense components of the mixture migrate away from the axis of the centrifuge, while less-dense components of the mixture migrate towards the axis. Chemists and biologists may increase the effective gravitational force on a test tube so as to move rapidly and completely cause the precipitate (‘’pellet”) to gather on the bottom of the tube. The remaining solution is properly called the “supernate” or ‘ supernatant liquid”. The supernatant liquid is then either quickly decanted from the tube without disturbing the precipitate, or withdrawn with a Pasteur pipette.
For example,
microcentrifuges are used to process small volumes of biological molecules, cells, or nuclei.
