 In a "hydride surface" the terminal groups are primarily -Si-H.The hydride surface can also be functionalized with carboxylic acids and long-chain alkyl groups.Mobile phases for ANPC are based on an organic solvent (such as methanol or acetonitrile) with a small amount of water; thus, the mobile phase is both "aqueous" (water is present) and "normal" (less polar than the stationary phase).