Phenyl columns provide unique selectivity when compared to aliphatic straight chain reversed-phase materials such as C18, C8, and C4. The π electrons of the phenyl group can interact with the aromatic ring(s) of an analyte to increase retention relative to non-aromatic species. Phenyl also has application as an alternative to C18 and C4 for the analysis of peptides and proteins on both small-pore (120Å) and wide-pore (300Å) silica supports. Retention is decreased on wide-pore phenyl phases relative to 120Å material. Generally, as pore size increases, surface area decreases, resulting in shorter retention times.