 The most popular column is an octadecyl carbon chain (C18)-bonded silica (USP classification L1).This is followed by C8-bonded silica (L7), pure silica (L3), cyano-bonded silica (L10) and phenyl-bonded silica (L11).Note that C18, C8 and phenyl are dedicated reversed-phase resins, while cyano columns can be used in a reversed-phase mode depending on analyte and mobile phase conditions.