An organic solvent/reagent-free and space-saving procedure for determining melamine residue in cow’s milk using 100% water in sample preparation and a reversed-phase high performance liquid chromatography (HPLC) equipped with diode array detector is described. Spiked and blank samples were prepared by homogenization with 100% water then centrifugal monolithic silica spin mini-column, MonoSpin®C18, with 100% water as an eluant. HPLC was performed on a ODS column with an isocratic 100% water mobile phase and diode array detector. The proposed method was validated by the analyses of spiked milk samples; resulting recoveries (≥ 96.8%; R.S.D. ≤ 2.0%), analytical total time (< 15 min/sample) and quantitation limit (0.05 μg/mL).