TRIS or tris(hydroxymethyl)aminomethane, is a hydrophilic basic compounds widely used in chemistry, biochemistry, and molecular biology. TRIS pKa (8.1) makes it an effective buffer in pH range of 7-9.2. TRIS is not retained on reversed-phase column and is not UV active, making it hard to be analyzed by HPLC. TRIS was analyzed by mixed-mode HPLC on a Primesep 100 column. Retention time of compound is controlled by the amount and pH of the buffer. No ion-pairing reagent is required for HPLC retention of hydrophilic basic molecules like TRIS. TRIS can be monitored by ELSD/CAD with trifluoroacetic acid in the mobile phase, or by LC/MS with ammonium formate or acetate in the mobile phase.