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Applications, advantages and disadvantages of Centrifugal field flow fractionation

Applications of the Centrifugal  Feild Flow Franctionation
This technique of characterization and separation is more efficient than all other techniques and separates a wide range of particles. The advantage of centrifugal FFF lies in the broad range of samples and high resolution that can be achieved by varying the speed and force applied. It is mostly used for biological separations and some of its applications are as follows:











The FFF in Heamatology
In 1989 rat lymphocytes were separated by using a new hybrid process coupled with Gravitational FFF and an adhesion mechanism. This experiment was carried out five years after the first publishment about FFF technique by Cladwell. In this new experiment the basic principle of separation is the duality of the relative strengths of adhesion of T and B cells and the hydrodynamic flow forces able to unbind theses cells. A scientist Urbankova used the Gravitational FFF technique and checked the size of RBC and showed that they can be separated acoording to their size. Later after that various scientists characterized, purified and separated the RBC on the basis of their size and density.






    The FFF in Infectiology
Sedimentation FFF has large effects and applications in bacteriology and parasitology. It is possible to separate the normal E. coli can be separated easily by Sedimentation FFF. In this case the separation is based upon the motility of the cell. If the cell is more motile it will be separated first due its higher diffusing capability. For the first time in history viruses were the first bioparticles to be characterized by their size, density and their molecular weight.

    Biotechnological applications of FFF
Various bioprocesses have been studied using Gravitational and Centrifugal FFF like the growth and cell cycle of yeast cells.

Advantages of FFF:
Advantages of the centrifugal FFF are given below:
Operating time
For maximum separation and less time consumption there should be a balance between flow force and the external applied force. And this technique these forces are always balanced by each other. So it is less time consuming process and the carries out fast characterization of the cellular species. In almost less than 15 minutes 0.1 retention ratios is obtained.

Recovery and integrity
This technique is non-destructive as the sample separated can be used for secondary characterization and small analyte concentration is used. As compared to all other techniques it gives better recovery and viability rates if the choice of the biocompatible material is adequate.







Selectivity
The multipolydispersity of the RBC is well known, these cells consist of various other sub-types differing in size, density and molecular weight. So the best way was thought to carry out the separation of RBC according to their volume because during their ageing RBCs increase in their density and become smaller. Later on Cardot separated RBCs on the basis of their age and showed the selectivity of Gravitational and Centrifugal FFF.





Disadvantages of FFF:
Some disadvantages or drawbacks of this technique are as follows:
Dilution
In order to carry out the separation by using Centrifugal FFF it is necessary that the particle-particle interactions or particle-wall interactions should be negligible. For this purpose it is necessary to dilute the sample to an extent that is why after fractionation it is necessary to enrich the sample.






Adsorption

The effective separation and characterization requires no interactions between the particles and the walls of the channel. But due to the externally applied field the particles are driven towards the wall of the channel. So the problem is the selection of such wall materials which have no adhesive capabilities. 



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