Seperation methods

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  • Created by: Vishaant
  • Created on: 03-04-16 14:00


Components of a mixture are separated based on differences in rate at which they are carried through a stationary phase by gaseous or liquid mobile phase 

Elution: the process of washing the componenet through the stationary phase with continuous flow of the mobile phase (the eluent)

-The components are identified by unique retention time. Factors afftecting tinclude velocity of mobile phase and chromatographic retention

Column Efficiency:
-expressed as plate height (H)
-we want the bands to be spread out. methods of doing this are:

1. Longitudinal diffusion
2.Resistance to mass transfer
3. Eddy diffusion

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High Performance Liquid Chromatography

-Solvent is forced through the column at high pressure of up to 400 atmosphers
-It allows you to use smaller particle size for column packing material giving it greater SA for interactions between stationary phasr and the molecules flowing past it.

*Normal Phase:
-polar stationary phase (silica) and non polar mobile phase (hexane)
-molecules elute in order of increasing polarity
-The more polar the mobile phase, the faster the elution of organic compound

*Reverse Phase:
-Non polar stationary phase (octadecysilane coated (ODS) silical gel) and polar mobile phase (water, methanol)
-The more lipophilic the mobile phase, the faster the elution of organic compound

Elution of ionisable components: alter pH of mobile phase 

-UV absorption or Fluorescence detector
-Refractive index detector 

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