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Sunday, September 5, 2021

Advantages and disadvantages of normal phase chromatography

Chromatography is a technique for separating the mixtures of substances into their constituents based on their molecular structure and composition. High-performance liquid chromatography is essentially a more advanced version of column liquid chromatography. Instead of allowing a solvent to flow naturally through a column, it is forced through at high pressures by the pump. Based on the phase system (stationary) in the process, HPLC has different types such as normal phase, reverse phase, size-exclusion, and ion-exchange HPLC.

What is NP chromatography?

Normal phase chromatography is a type of HPLC chromatography. In which the mobile phase is moderately polar and the stationary phase is used to separate the analytes, which are freely soluble in moderate solvents. Less polar molecules in NP-chromatography elute first than the polar molecules. The retention time (RT) of the analyte is reduced by the use of more polar solvents in the mobile phase. Normal phase chromatography is preferable to separate molecules that differ in functional groups.

Advantages of normal phase chromatography:

  • The major advantage of normal phase chromatography is that it is used for the separation of polar molecules.
  • The non-polar solvent can be used to dissolve a sample.
  • It is perfect for isomer isolation, and very hydrophilic or hydrophobic molecules.
  • NP-chromatography is the most preferred technique for column chromatography.
  • Using low viscosity solvents can have higher flow rates.
  • It can be used for compounds that can decompose in water.
  • Nonpolar hydrocarbons such as hexane, diethyl ether, chloroform, octane, and mixtures are used as mobile phases in normal phase chromatography which is also more common such as methanol and acetonitrile. etc.
  • The nature of the added solvent is controlled by solvent selectivity.

Disadvantages of normal phase chromatography:

  • This method of separation is not suitable for the analysis of a wide range of compounds.
  • Due to the solvent de-mixing, gradient elution is not possible in this type of HPLC.
  • The formation of bubbles and evaporation can cause by lower boiling point solvents.
  • It is difficult to control the strength of the solvent.
  • The retention time of components can be variable.


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