Brief Introduction of Mobile Phase Polarity
The essence of the chromatographic process is the process of distributing the equilibrium of the molecules of the substance to be separated between the stationary phase and the mobile phase. The distribution of the different substances between the two phases will be different, which causes the movement speed of the mobile phase to be different, with the flow. The movement of the phases separates the different components of the mixture from each other on the stationary phase.
Normal phase chromatography Liquid chromatography is divided into normal phase and reversed phase chromatography depending on the relative polarities of the mobile phase and the stationary phase.
The case where the polarity of the stationary phase is greater than the polarity of the mobile phase is called normal phase chromatography. Silica gel chromatography and polar bonded phase chromatography can be used for normal phase chromatography. The separation principle of normal phase chromatography is mainly based on the partition coefficient of the compound in the stationary phase and the mobile phase, and it is not suitable for separating geometric isomers.
In reversed-phase chromatography, the polarity of the mobile phase is stronger than that of the stationary phase. The separation principle is hydrophobic, also known as solvophobic. Reversed-phase chromatography is suitable for the separation of compounds bearing different hydrophobic groups, ie compounds of non-polar groups.