In mixed-mode HILIC chromatography, selectivity of separation can be adjusted by amount of acetonitrile, amount of buffer and buffer pH. Buffer concentration and pH will affect retention of ionizable compounds to a different degree. Retention of neutral compounds can be adjusted by the amount of acetonitrile. Carboxylic acid, three amino acids and two sugars are separated by combination of HILIC and ion-exchange mechanisms. Compounds can be monitored by ELSD, Corona (CAD), LC/MS or low UV. UV-transparent mobile phase /buffer is required for UV monitoring of this mixed-mode separation. This HPLC method can be adopted as general approach for analysis of sugars, amino acids and carboxylic acids.