Summary on the difference between positive and negative chro

Its essence is the difference of packing (stationary phase). The polarity of packing in normal phase is stronger than that in reversed phase.
Normal phase column
Most of the stationary phases used in normal chromatography are silica gel or silica gel columns with strong polar cyanogen group (- CN) and amine group (- NH3) on the surface of silica gel.
Reversed phase column
The packing used in reversed phase chromatography is usually based on silica gel. The surface bonded non-polar octadecyl functional group (ODS) is called C18 column. Other commonly used reversed phase columns are C8, C4, C2 and phenyl columns.
Normal phase column
The polarity of mobile phase used is weak. Such as hexane, chloroform, methylene chloride, etc.
Reversed phase column
The polarity of mobile phase used is strong. It is usually a mixture of water, buffer solution and methanol, acetonitrile, etc.
When running the liquid phase, the ratio of organic phase and aqueous phase can be adjusted to change the peak time of drugs. The organic phase usually includes acetonitrile, methanol, etc. The water phase is usually water, phosphoric acid water, etc.
Normal phase column
When the organic phase increases, the aqueous phase decreases and the peak appears later.
Reversed phase column
When the organic phase increases, the aqueous phase decreases and the peak appears earlier.
Normal phase column
The smaller the polarity of the component (drug), the earlier the peak appears.
Reversed phase column
The smaller the polarity of components (drugs), the later the peak appeared.
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