The media is chemically bonded with nonpolar alky chains such C4, C8 or C18 groups. The term reversed-phase describes the separation mode that just the opposite of the normal phase chromatography. In reversed-phase mode, non-polar or hydrophobic compounds are strongly retained, and polar samples are weakly retained, moving faster through the packing bed. The use of reversed-phase media for purification is becoming more popular because of its high reproducibility and broad applicability. A blend of water and miscible polar organic solvents such as acetonitrile or methanol is used as mobile phase to ensure the proper interaction of analytes with the non-polar alky packing surface. C18 or octadecyl silane (ODS) is the most popular type of reversed-phase packing. It applies to the separation of many compounds.