Polarity
The
arrangement of atoms and the corresponding bonds in a molecule determine its
activity, structure, and physiochemical properties. A particular arrangement of
these atoms and their corresponding bonds (called functional group) is
responsible for the characteristics and chemical reactions of the molecule.
This structure helps in finding out the polarity of the molecule. Hence, two
separation methods use these principles, Normal-Phase HPLC and Reversed-Phase
HPLC. The Normal-Phase HPLC has one non-polar mobile phase and one polar
stationary phase. The Reversed-Phase HPLC has one polar mobile phase and one
non-polar stationary phase.
Molecular
Size
This
separation characteristic is commonly used in Gel Permeation Chromatography
which separates analytes using the molecular size as the basis. Usually,
polymer analysis uses this technique.
Electrical
Charge
Contrary to polarity-based techniques, in
electrical charge-based techniques such as ion-Exchange Chromatography,
opposites attract and likes repel.
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