Although the use of alkyl phases, such as C 18 and C8, has dominated the applications in reversed-phase HPLC, their application in separation of polar compounds is limited.In recent years, polar embedded alky phase, fluorinated phase and other alternative phases have been developed to overcome the drawbacks of the alkyl phases.Because of the difference in retention mechanisms, they exhibit different retention and selectivity from conventional C 18 phase, and are often deployed for the separations not easily obtained using C18 phase.The applications of those phases have gained popularity in biopharmaceutical, pharmaceutical, natural product and environmental analyses.