XP tC18-AX is hybrid silica with reverse phase and anion exchange mixed mode, which is stablein the pH range of 2-10 and compatible with 100% aqueous phase. The design of XP tC18-AXwith positively charged functional groups enables it to generate ion exchange forces withnegatively charged compounds, thereby enhancing the retention of polar acidic compounds andproviding selectivity different from C18 columns. When analyzing alkaline compounds underacidic conditions, the retention of alkaline compounds is weakened due to the repulsive forcesbetween the same charges, and the tailing factor decreases, thereby improving the peak shapeof alkaline compounds.