According to the interaction between phases, which will define the method of sample separation, there are several types of liquid chromatography:
Normal phase chromatography.
Reverse phase chromatography.
Figure 1. General path flow in liquid chromatography.
Liquid chromatography typically uses the gravity force to pass the mobile phase through the stationary phase. However, when a significantly higher operational pressure (50-350 bar) is used to move the mobile phase through the system, the technique is called High-Performance liquid chromatography (HPLC).