Liquid chromatography is a type of chromatography where the mobile phase is a liquid, while the stationary phase can be solid or liquid.

According to the interaction between phases, which will define the method of sample separation, there are several types of liquid chromatography:

Schematic representation of sample flow in liquid chromatography. From the blue flask, named “mobile phase”, a grey arrow points towards the grey box, called “pump”, from which another arrow points towards the second grey box, named “injector”. From another blue flask, called “sample”, a grey arrow points towards the same grey box, called an “injector”. The arrow comes from the injector box towards the horizontally aligned cylinder, named “column - stationary phase”. From the column, the arrow points towards another grey box called “Detector”, from which an arrow goes to a blue flask named “Waste”. Finally, two lines go from the detector, one towards an image with a cylinder with tubes in it, called “Fraction collector”, and second one towards a computer screen named “Data acquisition”.
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).