Amino acids serve as building blocks, drugs and nutrients. The usual approach for analysis of amino acids include reversed-phase chromatography with an ion-pairing reagent, derivatization, and hydrophilic interaction chromatography (HILIC). Three amino acids (phenylalanine, tyrosine, and DOPA) were retained and separated in underivatized form in HILIC cation-exchange mode of core-shell mixed-mode HPLC column. This method is fast and reliable and provides base-line separation for all amino acids in the application. Method can be adopted for analysis of other amino acids.