Preparation Of Nicotine And Formaldehyde Molecularly Imprinted Polymer And Its Recognition Behavior In The Liquid And Gas Phase

In present work, nicotine and formaldehyde were utilized as target molecules toprepare molecularly imprinted monolithic column by different synthesis techniques andthe retention and adsorption behavior for these polymers in liquid phase and gas phaseenvironment were studied, respectively. All of work is abstracted as follows.（1）Synthesis of nicotine imprinted polymer (MIP)-derivatized silica monolithiccolumn was carried out based on in situ polymerization on the surface of macroporoussilica gel, as the matrix, which was first prepared in stainless column and thenchemically modified by using γ-MAPS. Structural characterization was performed byFTIR, SEM and the total pores volume and microspores volume measured based on sizeexclusion chromatography. In HPLC system, the retention and selective recognition ofMIP monolith were tested and chromatographic conditions influenced selectivity, suchas water content in the mobile phase, pH values of the buffer and column temperatureoptimized. Results showed that selectivity factor of nicotine, relative to8-hydroxyquinoline and pyridine, was4.31and2.95, and the optimized chromatographicconditions were pH=7.5. Additionally, frontal analysis was utilized for measuringabsorption isotherm and standard adsorption models for studying sites distribution onthe MIP monolithic column. Freundlich model was shown better than Langmuir modelto describe isotherm adsorption behavior of MIP monolith toward nicotine.Thermodynamic analysis indicated a spontaneous exothermic process for the adsorptionof template on the MIP monolithic column.（2）Above molecularly imprinted monolith was studied in present work. Thebinding capacity of the MIP monolith toward the template and its structural analoguewas evaluated by testing equilibrium adsorption amount through frontalchromatographic technique using NaH2PO4-Na2HPO4buffer solution containingnicotine as mobile phase. The influence of mobile phase pH value on adsorptioncapacity and elution recovery for this monolith were researched in detail and theoptimized loading and elution conditions used for solid phase extraction. Resultsindicated that the optimized pH values in loading and elution steps were pH5.0and9.0and the highest adsorption amount of nicotine on the MIP column and product recoveryin MIP solid phase extraction were6.4mg/L and99.6%, respectively. In addition, nogreat loss in recovery happened for this MIP monolith when it was used for twelveextraction cycles.（3）Nicotine molecularly imprinted monolith was studied by inverse gaschromatography (IGC) technique in its retention and adsorption characteristics. Nicotinemolecularly imprinted monolith fabricated by in-situ polymerization was acted as gaschromatographic stationary phase. Nicotine and its structural analogue pyridine was regarded as probe molecules in order to test its retention capacity, adsorption isothermand chromatographic thermodynamics characteristics to the compound. Results showedthat under the same chromatographic conditions, the capacity factors of the MIP weremuch higher than that of non-imprinted monolith, and the highest capacity factorreached87.88. The maximum separation factor of nicotine, relative to pyridine, was10.15. However, the capacity factor of nicotine imprinted column to the template wasincreased first and then decreased with injection volume, indicating that, to some extent,retention behavior of the column was not entirely consistent with that characteristic ofgeneral adsorbents. Adsorption heat for nicotine imprinted column to template orpyridine was obtained by testing chromatographic retention volume under differentcolumn temperature. The adsorption heat for template molecule on imprinted columnwas higher than that for pyridine. Chromatographic retention values and thechromatographic peaks were acquired at different injection volume. Results indicatedthat adsorption isotherm for nicotine on molecular imprinted column was in conformitywith BET Ⅱ adsorption type. However, adsorption isotherm for nicotine onnon-imprinted column and that for pyridine on both kinds of chromatographic columnwere approximately linear, fitting with Henry’s law.(4) Gas phase recognition of molecularly imprinted polymers (MIP), a metalion-mediated formaldehyde imprinted polymer which was prepared by using Co2+asmedia to coordinate with the template and functional monomer followed byco-polymerizing with crossing linker, was studied by inverse gas chromatography (IGC)technique. This MIP stationary phase was detected in recognition capability toward gasprobe molecules (formaldehyde and aldehyde) in order to evaluate chromatographyretention selectivity, isotherm adsorption and adsorption thermodynamics of thismaterial. Results endowed this MIP a much higher capacity factor to formaldehyde thanto aldehyde under the same chromatography conditions. The selectivity and capacityfactor for the MIP decreased with the increase of column temperature. From the gaschromatography plots obtained under various temperatures, adsorption thermodynamicparameters for the MIP toward the template and analogue can be calculated and byusing different injection volumes, the adsorption isotherms constructed. An approximatelinear adsorption isotherm for the template and a type of BET Ⅲ one for the analogueon the MIP was observed.