Abstract: By the reaction of aminopropyl triethoxy silane bonded silica phase with octodecanoyl chloride, a RP-HPLC packing with immobilized organic modifier for the separation of nitrogen-containing organic compounds was obtained. With this packing the separation of neutral organics is as good as the thaditional C₁₈ bonded phase while for good separation of basic organics neither inorganic salts nor organic modifiers such as organic acids or bases are required in the mobile phase.