This application shows the effect of mobile phase composition on retention of acidic, basic and neutral compound. Retention of basic and acidic compounds is controlled by buffer pH and concentration, while retention of neutral compound is controlled by the amount of acetonitrile. Buffer pH changes not only ionization state of ionizable basic and acidic compounds, but ionization state of trimodal stationary phase Obelisc R. Available detection techniques include UV, ELSD, LC/MS, and Corona.