A stationary phase for high-performance liquid chromatography including monofunctional primary silane functionalized silica provides improved separation performance for the preparative or process scale purification of cannabidiol (CBD) and tetrahydro-cannabinol (THC). Silica bonded with monofunctional primary silane(s) provides more efficient separation of these molecules through higher resolution values, reduced peak broadening and lower separation impedance, thus enabling higher purity product or more efficient purification process.