High performance liquid chromatography (HPLC) is a very powerful technique that can be used to identify, quantify or purify components of a mixture.
As shown below, HPLC uses a column filled with fine beads that form the stationary phase and a solvent (or mobile phase) that moves over the stationary phase in the column due to the pressure generated by the pump.
HPLC output is recorded as a chromatogram. Compounds that interact the least with the stationary phase, move faster and have a shorter retention time. Compounds that interact the most with the stationary phase, move slower and have a longer retention time.
Figure 1. Components of an HPLC instrument