CHROMATOGRAPHY - Basic defintion and idea

          Definition:

Chromatography is defined as a procedure by which solutes are separated by

dynamic differential migration process in a system consisting of two or more
phases, one of which moves continuously in a given direction and in which the
individual substances exhibit different mobilities by reason of differences in
adsorption, partition, solubility, vapor pressure, molecular size, or ionic charge
density.
Greek words chroma and graphs meaning “color” and “writing” respectively.

Discovery of chromatography

❑ Chromatography is relatively a new technique that was first invented by M. Tswett, a botanist in 1906 in Warsaw.

❑ In that year, he was successful in doing the separation of chlorophyll, xanthophyll and several other colored substances by percolating vegetable extracts through a column of calcium carbonate.

❑ The separated species appeared as colored bands on the column, which accounts for the name he chose for the method (Greek chroma meaning "color“ and graphing meaning "writing"),

❑ The tremendous impact of these methods on science is attested by the 1952 Nobel Prize in Chemistry that was awarded to A. J P, Martin and R. LM, Synge for their discoveries in the field.

Advantages of Chromatographic Processes:

❑ Capable of separating complex mixtures at low operating temperatures

❑Large scale batch or continuous operation possible

❑Capable of separating materials according to size and/or chemical properties

❑Can be used to separate delicate or heat-labile compounds

❑Separation can be achieved by a variety of methods

❑Very pure products can be recovered

Disadvantages of Chromatographic Processes

❑ Process scale-up is a problem (hence low throughput)

 ❑ Irreversible adsorption of materials creates problems 

❑ To achieve efficient separations, high operating pressures may be required.

 ❑ Over-loading of columns with feed material may cause incomplete separation

 ❑ Feed material is diluted by flowing mobile phase 

❑ Non-uniform column packing can lead to a significant decrease in separation 

performance

 ❑ Pre-filtration of feed material is usually required 

❑ Periodic column re-packing / regeneration required

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