The PRP-C18 reversed-phase HPLC column expands the pH range of reversed-phase chromatography, providing separations over an extended column life. Stability to pH extremes extends the application of reversed-phase chromatography to the separation of amines and other organic bases. The rigid stationary phase of the PRP-C18 is stable mechanically (up to 5,000 psi) and thermally (greater than 100°C), which can enable separations at high temperatures and pressures, shorten run times, and requires less organic solvent.