Purospher® HPLC columns are based on high purity, metal-free silica for outstanding separations with excellent peak symmetry. This makes them the ideal choice for modern Reverse Phase HPLC. Phenyl phases are π-basic (electron donating) and are similar in overall retention to alkyl and EPG phases for easy column screening. The alternate selectivity of phenyl phases is often explained by the π-π interactions available through the phenyl ring.