Preparation And Evaluation Of Low Cross-Linked Molecularly Imprinted Monolithic Column

Molecularly imprinted polymers (MIPs) are new technique for synthesizing the stationary phase with the ability of pre-selectivity and monolithic column is is a new type of chromatographic stationary phases. The combination of monolithic column and MIPs will be the chromatographic stationary phases with potential applications and play an important role in the area of analytical chemistry. Synthesised of low cross-linked imprinted monolithic columns with different methods, and different synthesize conditions, chromatographic conditions and the characteristic of MIP columns were systematically investigated. The results as follows:1Molecular crowding is a new approach to promoting molecular imprinting more efficiently. In this work, this concept was applied to the preparation of low cross-linked imprinted polymers in the presence of an immobilised template for stabilizing binding sites and improving molecular recognition. An imprinted monolithic column was synthesized using a mixture of2,4-diamino-6-methyl-1,3,5-triazine (template),2,4-diamino-6-(methacryloyloxy) ethyl-1,3,5-triazine (polymerisable template), methacrylic acid, ethylene glycol dimethacrylate, and polystyrene (molecular crowding agent). Some polymerization factors, such as template-monomer molar ratio, the composition of the porogen and crosslinking density, on the imprinting effect of resulting MIP monolith were systematically investigated. The results indicated that the imprinted monolithic columns prepared in the presence of molecular crowding agent retained affinity and specificity for template even when prepared with a level of cross-linker as low as9%. Moreover, a stoichiometric displacement model for retention was successfully applied to evaluate the interaction between the solute and the stationary phase. Compared with the low cross-linked MIP prepared by conventional polymerization, the molecular crowding-based low cross-linked monolithic MIPs showed higher selectivity. The results suggested that molecular crowding is a powerful strategy to increase the effect of molecular imprinting at a low level of crosslinker.2A new approach based on liquid crystal with recognition ability is demonstrated for synthesis of molecularly imprinted polymer in a low level of crosslinking. The monolithic skeleton in a stainless steel column was prepared with a solution of TRIM with a mixture of isooctane and toluene as porogen. The prepolymerization mixture which had S-ofloxacin (template) and liquid crystalline monomer was pumped into the monolithic column. Some important parameters in the preparation, i.e., Second polymerization time, crosslinking density and different kinds of liquid crystalline monomer were investigated. The resulting low crosslinking (26%) molecularly imprinted polymer exhibited excellent retention capability and large imprinted factor for template (the retention factor and imprinted factor for S ofloxacin on MIP column were14.04and12.33, respectively). The resolution of enatiomers separation achieved on the S-ofloxacin-imprinted column was up to1.59. Performance of imprinting comparable to that recorded in conventional MIP stationary phase was observed even in a crosslinking degree of10%. The results illustrate that the synthesis of low crosslinked MIP based on liquid crystal is an approach to producing chiral stationary phase comparable to other chiral stationary phase.