Supelco Supel-Select HLB SPE is a hydrophilic modified styrene based polymer developed for the solid phase extraction of a highly broad range of compounds from aqueous samples. The retention mechanism is predominately based on reversed-phase interaction. However, because the phase is hydrophilic modified, the phase is also selective for more polar compounds. Examples of more polar compounds that are retained and recovered on Supel-Select HLB include (but not limited to): pyridoxine (logPo/w 0.56), riboflavin (logPo/w 2.02), biotin (logPo/w 0.11).