High-performance liquid chromatography (HPLC) is a technique in analytic chemistry used to separate the components in a mixture, to identify each component, and to quantify each component. How it works is very similar to column chromatography. Each component interacts differently with the absorbent material. One widely used absorbent material is silica gel. The difference in polarity will result in different flow rates for the different components, leading to the separation of the components as they flow out the column. The difference between column chromatography and HPLC is column chromatography flashes nitrogen to the column to speed up the separation. However, HPLC passes a pressurized liquid solvent containing the sample mixture through the column.