Preparation of 4-aminopyridine imprinted polymer-based monolithic capillary column and evaluation of electrochromatography

The 4-aminopyridine(4-AP) molecularly imprinted polymer (MIP)-based monolithic capillary column was prepared by an in situ thermal-initiated polymerization process; the preparation process is simple and quick. The MIP was covalently linked to the inner wall of fused silica capillary. The performance of the column was evaluated by capillary electrochromatography (CEC). Under the optimal CEC conditions, the resolution of 4-AP and 2-AP was 2.5 on the 4-AP MIP based monolithic column, while only 0.35 on the reference column without any imprint of 4-AP. The recognition ability of MIP for 4-AP was influenced by a lot of factors including pH, sort of buffers, ionic strength and the content of organic modifier in the mobile phase. The recognition of the MIP was enhanced with decreasing the salt concentration of the buffer or increasing the acetonitrile content in the mobile phase. The phenomena are ascribed to the reduction in the amount of cationic ions in the mobile phase, which compete with 4-AP in combination with carboxyl in the cavity of MIP, and weaken the specific affinity of the imprint cavity for the imprinted molecule. The effect of the sort and pH of buffer on the recognition of the MIP is complicated. For phosphate buffer, the effect of pH is parabolic, giving the best recognition at pH=5, while for acetate buffer, increase in pH benefits the recognition.