Purospher® RP-18 is designed for the separation of problematic basic compounds with simple neutral eluents. In addition Purospher® RP-18 allows the separation of hydrophilic compounds with aqueous mobile phase. Purospher® RP-18 is based upon a high-purity, metal free silica. The multi-step chemical modification and deactivation of the surface enables a peak-tailing free elution of basic and chelating compounds. Purospher® RP-18 is not suitable for the separation of acidic compounds. The good chemical stability of Purospher® RP-18 enables the use of mobile phase conditions at pH 8 for a long period of time.