a College of Pharmacy, Tianjin Medical University, Tianjin 300070, China
b State Key Laboratory of Element-organic Chemistry, Institute of Element Organic Chemistry,
Nankai University, Tianjin 300071, China
c National Chromatographic Research and Analysis Center, Dalian Institute of Chemical Physics,
Chinese Academy of Sciences, Dalian 116023, China

A tetrapeptide-imprinted capillary monolithic column was synthesized successfully in the presence of YPLG (Tyr-Pro-Leu-Gly) as template by in situ thermo-initiated polymerization. For exploring the recognition mechanism of molecularly imprinted polymer in a capillary electrochromatography (CEC) mode, YPLG and its structural analogue, YPGL (Tyr-Pro-Gly-Leu), differing in amino acid sequence, were used as model compounds. It is hard work to separate the two tetrapeptides by a simple CEC or a capillary electrophoresis mode due to their similar chemical structures and values of pI. However, the results showed that YPLG could be recognized specially by the imprinted monolith. The separation factor (α’) and the resolution (Rs) between YPLG and YPGL were 1.73 and 3.72, respectively. The effects of organic modifier concentration, pH value of buffer, salt concentration of buffer and column temperature on the recognition of YPLG and YPGL were investigated. A non-linear Van’t Hoff behavior of the template was observed on a YPLG-imprinted column, which suggested the presence of multiple types of retention mechanisms or multiple types of binding sites. The results showed that the molecular recognition on MIP monolith in the CEC mode mainly derived from hydrogen bonding between YPLG and MIP and three-dimensional structure of the imprinting cavities.